Metadata-Version: 2.0
Name: zc.buildout
Version: 2.4.3
Summary: System for managing development buildouts
Home-page: http://buildout.org
Author: Jim Fulton
Author-email: jim@zope.com
License: ZPL 2.1
Keywords: development build
Platform: UNKNOWN
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Zope Public License
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 2.6
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.2
Classifier: Programming Language :: Python :: 3.3
Classifier: Programming Language :: Python :: 3.4
Classifier: Topic :: Software Development :: Build Tools
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Requires-Dist: setuptools (>=8.0)
Provides-Extra: test
Requires-Dist: manuel; extra == 'test'
Requires-Dist: zope.testing; extra == 'test'

********
Buildout
********

.. image:: https://secure.travis-ci.org/buildout/buildout.png?branch=master
   :width: 82px
   :height: 13px
   :alt: Travis CI build report
   :target: https://travis-ci.org/buildout/buildout

.. image:: http://winbot.zope.org/buildstatusimage?builder=zc_buildout_dev%20py_270_win32%20master&number=-1
   :width: 82px
   :height: 13px
   :alt: winbot build report
   :target: http://winbot.zope.org/builders/zc_buildout_dev%20py_270_win32%20master/builds/-1

Buildout is a project designed to solve 2 problems:

1. Application-centric assembly and deployment

   *Assembly* runs the gamut from stitching together libraries to
   create a running program, to production deployment configuration of
   applications, and associated systems and tools (e.g. run-control
   scripts, cron jobs, logs, service registration, etc.).

   Buildout might be confused with build tools like make or ant, but
   it is a little higher level and might invoke systems like make or
   ant to get its work done.

   Buildout might be confused with systems like puppet or chef, but it
   is more application focused.  Systems like puppet or chef might
   use buildout to get their work done.

   Buildout is also somewhat Python-centric, even though it can be
   used to assemble and deploy non-python applications.  It has some
   special features for assembling Python programs. It's scripted with
   Python, unlike, say puppet or chef, which are scripted with Ruby.

2. Repeatable assembly of programs from Python software distributions

   Buildout puts great effort toward making program assembly a highly
   repeatable process, whether in a very open-ended development mode,
   where dependency versions aren't locked down, or in a deployment
   environment where dependency versions are fully specified.  You
   should be able to check buildout into a VCS and later check it out.
   Two checkouts built at the same time in the same environment should
   always give the same result, regardless of their history.  Among
   other things, after a buildout, all dependencies should be at the
   most recent version consistent with any version specifications
   expressed in the buildout.

   Buildout supports applications consisting of multiple programs,
   with different programs in an application free to use different
   versions of Python distributions.  This is in contrast with a
   Python installation (real or virtual), where, for any given
   distribution, there can only be one installed.

To learn more about buildout, including how to use it, see
http://buildout.org/.


Installation
************

There are a number of ways to install buildout.  You can install it as
you would any other package, using pip or easy_install.  In this case,
you'll get a buildout command that you can use to build projects.  To
build a project, just use::

  buildout

from a project directory.

Buildout's (stubborn) philosophy, however, is that projects should be
self-contained, and not require changes to a shared Python
installation. To avoid changing a shared Python installation you can
download a bootstrap script that, when run, will install buildout
locally in your project.

The bootstrap script for buildout version 2 is at:

  https://bootstrap.pypa.io/bootstrap-buildout.py

So, for example, to install buildout 2 in a project, you might::

  wget https://bootstrap.pypa.io/bootstrap-buildout.py
  python bootstrap-buildout.py

Then to build your project, you can just run::

  bin/buildout

from the project directory.

buildout 2 is somewhat backward-incompatible with version 1.  Most
projects will probably work fine with either.  If you need to keep
using version 1, however, specify a version requirement when you use
pip or easy_install, or use the version 1 bootstrap script at:

  http://downloads.buildout.org/1/bootstrap.py


Below, you'll find doctest-based documentation.  It was an experiment
in reusing tests as documentation.  The experiment didn't go that
well, but there may be details below that aren't easy to find on
buildout.org yet.

.. contents ::

doctest-based Documentation
***************************

Buildouts
=========

The word "buildout" refers to a description of a set of parts and the
software to create and assemble them.  It is often used informally to
refer to an installed system based on a buildout definition.  For
example, if we are creating an application named "Foo", then "the Foo
buildout" is the collection of configuration and application-specific
software that allows an instance of the application to be created.  We
may refer to such an instance of the application informally as "a Foo
buildout".

This document describes how to define buildouts using buildout
configuration files and recipes.  There are three ways to set up the
buildout software and create a buildout instance:

1. Install the zc.buildout egg with easy_install and use the buildout
   script installed in a Python scripts area.

2. Use the buildout bootstrap script to create a buildout that
   includes both the setuptools and zc.buildout eggs.  This allows you
   to use the buildout software without modifying a Python install.
   The buildout script is installed into your buildout local scripts
   area.

3. Use a buildout command from an already installed buildout to
   bootstrap a new buildout.  (See the section on bootstraping later
   in this document.)

Often, a software project will be managed in a software repository,
such as a subversion repository, that includes some software source
directories, buildout configuration files, and a copy of the buildout
bootstrap script.  To work on the project, one would check out the
project from the repository and run the bootstrap script which
installs setuptools and zc.buildout into the checkout as well as any
parts defined.

We have a sample buildout that we created using the bootstrap command
of an existing buildout (method 3 above).  It has the absolute minimum
information.  We have bin, develop-eggs, eggs and parts directories,
and a configuration file:

    >>> ls(sample_buildout)
    d  bin
    -  buildout.cfg
    d  develop-eggs
    d  eggs
    d  parts

The bin directory contains scripts.

    >>> ls(sample_buildout, 'bin')
    -  buildout

    >>> ls(sample_buildout, 'eggs')
    -  setuptools-0.7-py3.3.egg
    -  zc.buildout.egg-link

The develop-eggs and parts directories are initially empty:

    >>> ls(sample_buildout, 'develop-eggs')
    >>> ls(sample_buildout, 'parts')

The develop-eggs directory holds egg links for software being
developed in the buildout.  We separate develop-eggs and other eggs to
allow eggs directories to be shared across multiple buildouts.  For
example, a common developer technique is to define a common eggs
directory in their home that all non-develop eggs are stored in.  This
allows larger buildouts to be set up much more quickly and saves disk
space.

The parts directory provides an area where recipes can install
part data.  For example, if we built a custom Python, we would
install it in the part directory.  Part data is stored in a
sub-directory of the parts directory with the same name as the part.

Buildouts are defined using configuration files.  These are in the
format defined by the Python ConfigParser module, with extensions
that we'll describe later.  By default, when a buildout is run, it
looks for the file buildout.cfg in the directory where the buildout is
run.

The minimal configuration file has a buildout section that defines no
parts:

    >>> cat(sample_buildout, 'buildout.cfg')
    [buildout]
    parts =

A part is simply something to be created by a buildout.  It can be
almost anything, such as a Python package, a program, a directory, or
even a configuration file.

Recipes
-------

A part is created by a recipe.  Recipes are always installed as Python
eggs. They can be downloaded from a package server, such as the
Python Package Index, or they can be developed as part of a project
using a "develop" egg.

A develop egg is a special kind of egg that gets installed as an "egg
link" that contains the name of a source directory.  Develop eggs
don't have to be packaged for distribution to be used and can be
modified in place, which is especially useful while they are being
developed.

Let's create a recipe as part of the sample project.  We'll create a
recipe for creating directories.  First, we'll create a recipes source
directory for our local recipes:

    >>> mkdir(sample_buildout, 'recipes')

and then we'll create a source file for our mkdir recipe:

    >>> write(sample_buildout, 'recipes', 'mkdir.py',
    ... """
    ... import logging, os, zc.buildout
    ...
    ... class Mkdir:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         self.name, self.options = name, options
    ...         options['path'] = os.path.join(
    ...                               buildout['buildout']['directory'],
    ...                               options['path'],
    ...                               )
    ...         if not os.path.isdir(os.path.dirname(options['path'])):
    ...             logging.getLogger(self.name).error(
    ...                 'Cannot create %s. %s is not a directory.',
    ...                 options['path'], os.path.dirname(options['path']))
    ...             raise zc.buildout.UserError('Invalid Path')
    ...
    ...
    ...     def install(self):
    ...         path = self.options['path']
    ...         logging.getLogger(self.name).info(
    ...             'Creating directory %s', os.path.basename(path))
    ...         os.mkdir(path)
    ...         return path
    ...
    ...     def update(self):
    ...         pass
    ... """)

Currently, recipes must define 3 methods:

- a constructor,

- an install method, and

- an update method.

The constructor is responsible for updating a parts options to reflect
data read from other sections.  The buildout system keeps track of
whether a part specification has changed.  A part specification has
changed if it's options, after adjusting for data read from other
sections, has changed, or if the recipe has changed.  Only the options
for the part are considered.  If data are read from other sections,
then that information has to be reflected in the parts options.  In
the Mkdir example, the given path is interpreted relative to the
buildout directory, and data from the buildout directory is read.  The
path option is updated to reflect this.  If the directory option was
changed in the buildout sections, we would know to update parts
created using the mkdir recipe using relative path names.

When buildout is run, it saves configuration data for installed parts
in a file named ".installed.cfg".  In subsequent runs, it compares
part-configuration data stored in the .installed.cfg file and the
part-configuration data loaded from the configuration files as
modified by recipe constructors to decide if the configuration of a
part has changed. If the configuration has changed, or if the recipe
has changed, then the part is uninstalled and reinstalled.  The
buildout only looks at the part's options, so any data used to
configure the part needs to be reflected in the part's options.  It is
the job of a recipe constructor to make sure that the options include
all relevant data.

Of course, parts are also uninstalled if they are no-longer used.

The recipe defines a constructor that takes a buildout object, a part
name, and an options dictionary. It saves them in instance attributes.
If the path is relative, we'll interpret it as relative to the
buildout directory.  The buildout object passed in is a mapping from
section name to a mapping of options for that section. The buildout
directory is available as the directory option of the buildout
section.  We normalize the path and save it back into the options
directory.

The install method is responsible for creating the part.  In this
case, we need the path of the directory to create.  We'll use a path
option from our options dictionary.  The install method logs what it's
doing using the Python logging call.  We return the path that we
installed.  If the part is uninstalled or reinstalled, then the path
returned will be removed by the buildout machinery.  A recipe install
method is expected to return a string, or an iterable of strings
containing paths to be removed if a part is uninstalled.  For most
recipes, this is all of the uninstall support needed. For more complex
uninstallation scenarios use `Uninstall recipes`_.

The update method is responsible for updating an already installed
part.  An empty method is often provided, as in this example, if parts
can't be updated.  An update method can return None, a string, or an
iterable of strings.  If a string or iterable of strings is returned,
then the saved list of paths to be uninstalled is updated with the new
information by adding any new files returned by the update method.

We need to provide packaging information so that our recipe can be
installed as a develop egg. The minimum information we need to specify
is a name.  For recipes, we also need to define the
names of the recipe classes as entry points.  Packaging information is
provided via a setup.py script:

    >>> write(sample_buildout, 'recipes', 'setup.py',
    ... """
    ... from setuptools import setup
    ...
    ... setup(
    ...     name = "recipes",
    ...     entry_points = {'zc.buildout': ['mkdir = mkdir:Mkdir']},
    ...     )
    ... """)

Our setup script defines an entry point. Entry points provide
a way for an egg to define the services it provides.  Here we've said
that we define a zc.buildout entry point named mkdir.  Recipe
classes must be exposed as entry points in the zc.buildout group.  we
give entry points names within the group.

We also need a README.txt for our recipes to avoid an annoying warning
from distutils, on which setuptools and zc.buildout are based:

    >>> write(sample_buildout, 'recipes', 'README.txt', " ")

Now let's update our buildout.cfg:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = mystuff
    ... """)

Let's go through the changes one by one::

    develop = recipes

This tells the buildout to install a development egg for our recipes.
Any number of paths can be listed.  The paths can be relative or
absolute.  If relative, they are treated as relative to the buildout
directory.  They can be directory or file paths.  If a file path is
given, it should point to a Python setup script.  If a directory path
is given, it should point to a directory containing a setup.py file.
Development eggs are installed before building any parts, as they may
provide locally-defined recipes needed by the parts.

::

    parts = data-dir

Here we've named a part to be "built".  We can use any name we want
except that different part names must be unique and recipes will often
use the part name to decide what to do.

::

    [data-dir]
    recipe = recipes:mkdir
    path = mystuff


When we name a part, we also create a section of the same
name that contains part data.  In this section, we'll define
the recipe to be used to install the part.  In this case, we also
specify the path to be created.

Let's run the buildout.  We do so by running the build script in the
buildout:

    >>> import os
    >>> os.chdir(sample_buildout)
    >>> buildout = os.path.join(sample_buildout, 'bin', 'buildout')
    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Installing data-dir.
    data-dir: Creating directory mystuff

We see that the recipe created the directory, as expected:

    >>> ls(sample_buildout)
    -  .installed.cfg
    d  bin
    -  buildout.cfg
    d  develop-eggs
    d  eggs
    d  mystuff
    d  parts
    d  recipes

In addition, .installed.cfg has been created containing information
about the part we installed:

    >>> cat(sample_buildout, '.installed.cfg')
    [buildout]
    installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
    parts = data-dir
    <BLANKLINE>
    [data-dir]
    __buildout_installed__ = /sample-buildout/mystuff
    __buildout_signature__ = recipes-c7vHV6ekIDUPy/7fjAaYjg==
    path = /sample-buildout/mystuff
    recipe = recipes:mkdir

Note that the directory we installed is included in .installed.cfg.
In addition, the path option includes the actual destination
directory.

If we change the name of the directory in the configuration file,
we'll see that the directory gets removed and recreated:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = mydata
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling data-dir.
    Installing data-dir.
    data-dir: Creating directory mydata

    >>> ls(sample_buildout)
    -  .installed.cfg
    d  bin
    -  buildout.cfg
    d  develop-eggs
    d  eggs
    d  mydata
    d  parts
    d  recipes

If any of the files or directories created by a recipe are removed,
the part will be reinstalled:

    >>> rmdir(sample_buildout, 'mydata')
    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling data-dir.
    Installing data-dir.
    data-dir: Creating directory mydata

Error reporting
---------------

If a user makes an error, an error needs to be printed and work needs
to stop.  This is accomplished by logging a detailed error message and
then raising a (or an instance of a subclass of a)
zc.buildout.UserError exception.  Raising an error other than a
UserError still displays the error, but labels it as a bug in the
buildout software or recipe. In the sample above, of someone gives a
non-existent directory to create the directory in:


    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = /xxx/mydata
    ... """)

We'll get a user error, not a traceback.

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    data-dir: Cannot create /xxx/mydata. /xxx is not a directory.
    While:
      Installing.
      Getting section data-dir.
      Initializing section data-dir.
    Error: Invalid Path


Recipe Error Handling
---------------------

If an error occurs during installation, it is up to the recipe to
clean up any system side effects, such as files created.  Let's update
the mkdir recipe to support multiple paths:

    >>> write(sample_buildout, 'recipes', 'mkdir.py',
    ... """
    ... import logging, os, zc.buildout
    ...
    ... class Mkdir:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         self.name, self.options = name, options
    ...
    ...         # Normalize paths and check that their parent
    ...         # directories exist:
    ...         paths = []
    ...         for path in options['path'].split():
    ...             path = os.path.join(buildout['buildout']['directory'], path)
    ...             if not os.path.isdir(os.path.dirname(path)):
    ...                 logging.getLogger(self.name).error(
    ...                     'Cannot create %s. %s is not a directory.',
    ...                     options['path'], os.path.dirname(options['path']))
    ...                 raise zc.buildout.UserError('Invalid Path')
    ...             paths.append(path)
    ...         options['path'] = ' '.join(paths)
    ...
    ...     def install(self):
    ...         paths = self.options['path'].split()
    ...         for path in paths:
    ...             logging.getLogger(self.name).info(
    ...                 'Creating directory %s', os.path.basename(path))
    ...             os.mkdir(path)
    ...         return paths
    ...
    ...     def update(self):
    ...         pass
    ... """)

..

    >>> clean_up_pyc(sample_buildout, 'recipes', 'mkdir.py')

If there is an error creating a path, the install method will exit and
leave previously created paths in place:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = foo bin
    ... """)

    >>> print_(system(buildout)) # doctest: +ELLIPSIS
    Develop: '/sample-buildout/recipes'
    Uninstalling data-dir.
    Installing data-dir.
    data-dir: Creating directory foo
    data-dir: Creating directory bin
    While:
      Installing data-dir.
    <BLANKLINE>
    An internal error occurred due to a bug in either zc.buildout or in a
    recipe being used:
    Traceback (most recent call last):
    ... exists...

We meant to create a directory bins, but typed bin.  Now foo was
left behind.

    >>> os.path.exists('foo')
    True

If we fix the typo:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = foo bins
    ... """)

    >>> print_(system(buildout)) # doctest: +ELLIPSIS
    Develop: '/sample-buildout/recipes'
    Installing data-dir.
    data-dir: Creating directory foo
    While:
      Installing data-dir.
    <BLANKLINE>
    An internal error occurred due to a bug in either zc.buildout or in a
    recipe being used:
    Traceback (most recent call last):
    ... exists...

Now they fail because foo exists, because it was left behind.

    >>> remove('foo')

Let's fix the recipe:

    >>> write(sample_buildout, 'recipes', 'mkdir.py',
    ... """
    ... import logging, os, zc.buildout, sys
    ...
    ... class Mkdir:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         self.name, self.options = name, options
    ...
    ...         # Normalize paths and check that their parent
    ...         # directories exist:
    ...         paths = []
    ...         for path in options['path'].split():
    ...             path = os.path.join(buildout['buildout']['directory'], path)
    ...             if not os.path.isdir(os.path.dirname(path)):
    ...                 logging.getLogger(self.name).error(
    ...                     'Cannot create %s. %s is not a directory.',
    ...                     options['path'], os.path.dirname(options['path']))
    ...                 raise zc.buildout.UserError('Invalid Path')
    ...             paths.append(path)
    ...         options['path'] = ' '.join(paths)
    ...
    ...     def install(self):
    ...         paths = self.options['path'].split()
    ...         created = []
    ...         try:
    ...             for path in paths:
    ...                 logging.getLogger(self.name).info(
    ...                     'Creating directory %s', os.path.basename(path))
    ...                 os.mkdir(path)
    ...                 created.append(path)
    ...         except Exception:
    ...             for d in created:
    ...                 os.rmdir(d)
    ...                 assert not os.path.exists(d)
    ...                 logging.getLogger(self.name).info(
    ...                     'Removed %s due to error',
    ...                      os.path.basename(d))
    ...             sys.stderr.flush()
    ...             sys.stdout.flush()
    ...             raise
    ...
    ...         return paths
    ...
    ...     def update(self):
    ...         pass
    ... """)

..

    >>> clean_up_pyc(sample_buildout, 'recipes', 'mkdir.py')

And put back the typo:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = foo bin
    ... """)

When we rerun the buildout:

    >>> print_(system(buildout)) # doctest: +ELLIPSIS
    Develop: '/sample-buildout/recipes'
    Installing data-dir.
    data-dir: Creating directory foo
    data-dir: Creating directory bin
    data-dir: Removed foo due to error
    While:
      Installing data-dir.
    <BLANKLINE>
    An internal error occurred due to a bug in either zc.buildout or in a
    recipe being used:
    Traceback (most recent call last):
    ... exists...

we get the same error, but we don't get the directory left behind:

    >>> os.path.exists('foo')
    False

It's critical that recipes clean up partial effects when errors
occur.  Because recipes most commonly create files and directories,
buildout provides a helper API for removing created files when an
error occurs.  Option objects have a created method that can be called
to record files as they are created.  If the install or update method
returns with an error, then any registered paths are removed
automatically.  The method returns the files registered and can be
used to return the files created.  Let's use this API to simplify the
recipe:

    >>> write(sample_buildout, 'recipes', 'mkdir.py',
    ... """
    ... import logging, os, zc.buildout
    ...
    ... class Mkdir:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         self.name, self.options = name, options
    ...
    ...         # Normalize paths and check that their parent
    ...         # directories exist:
    ...         paths = []
    ...         for path in options['path'].split():
    ...             path = os.path.join(buildout['buildout']['directory'], path)
    ...             if not os.path.isdir(os.path.dirname(path)):
    ...                 logging.getLogger(self.name).error(
    ...                     'Cannot create %s. %s is not a directory.',
    ...                     options['path'], os.path.dirname(options['path']))
    ...                 raise zc.buildout.UserError('Invalid Path')
    ...             paths.append(path)
    ...         options['path'] = ' '.join(paths)
    ...
    ...     def install(self):
    ...         paths = self.options['path'].split()
    ...         for path in paths:
    ...             logging.getLogger(self.name).info(
    ...                 'Creating directory %s', os.path.basename(path))
    ...             os.mkdir(path)
    ...             self.options.created(path)
    ...
    ...         return self.options.created()
    ...
    ...     def update(self):
    ...         pass
    ... """)

..

    >>> clean_up_pyc(sample_buildout, 'recipes', 'mkdir.py')

We returned by calling created, taking advantage of the fact that it
returns the registered paths.  We did this for illustrative purposes.
It would be simpler just to return the paths as before.

If we rerun the buildout, again, we'll get the error and no
directories will be created:

    >>> print_(system(buildout)) # doctest: +ELLIPSIS
    Develop: '/sample-buildout/recipes'
    Installing data-dir.
    data-dir: Creating directory foo
    data-dir: Creating directory bin
    While:
      Installing data-dir.
    <BLANKLINE>
    An internal error occurred due to a bug in either zc.buildout or in a
    recipe being used:
    Traceback (most recent call last):
    ... exists...

    >>> os.path.exists('foo')
    False

Now, we'll fix the typo again and we'll get the directories we expect:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = foo bins
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Installing data-dir.
    data-dir: Creating directory foo
    data-dir: Creating directory bins

    >>> os.path.exists('foo')
    True
    >>> os.path.exists('bins')
    True

Configuration file syntax
-------------------------

A buildout configuration file consists of a sequence of sections.  A
section has a section header followed by 0 or more section options.
(Buildout configuration files may be viewed as a variation on INI
files.)

A section header consists of a section name enclosed in square braces.
A section name consists of one or more non-whitespace characters other
than square braces ('[', ']'), curly braces ('{', '}'), colons (':')
or equal signs ('='). Whitespace surrounding section names is ignored.

A section header can optionally have a condition expression separated
by a colon.  See `Conditional sections`_.

Options consist of option names, followed by optional space or tab
characters, an optional plus or minus sign and an equal signs and
values.  An option value may be spread over multiple lines as long as
the lines after the first start with a whitespace character.  An
option name consists of one or more non-whitespace characters other
than equal signs, square braces ("[", "]"), curly braces ("{", "}"),
plus signs or colons (":"). The option name '<' is reserved.  An
option's data consists of the characters following the equal sign on
the start line, plus the continuation lines.

Option values have extra whitespace stripped.  How this is done
depends on whether the value has non-whitespace characterts on the
first line.  If an option value has non-whitespace characters on the
first line, then each line is stripped and blank lines are removed.
For example, in::

  [foo]
  bar = 1
  baz = a
        b

        c

.. -> text

    >>> try: import StringIO
    ... except ImportError: import io as StringIO
    >>> import pprint, zc.buildout.configparser
    >>> pprint.pprint(zc.buildout.configparser.parse(StringIO.StringIO(
    ...     text), 'test'))
    {'foo': {'bar': '1', 'baz': 'a\nb\nc'}}

The value of of ``bar`` is ``'1'`` and the value of ``baz`` is
``'a\nb\nc'``.

If the first line of an option doesn't contain whitespace, then the
value is dedented (with ``textwrap.dedent``), trailing spaces in lines
are removed, and leading and trailing blank lines are removed.  For
example, in::


  [foo]
  bar =
  baz =

    a
      b

    c

.. -> text

    >>> pprint.pprint(zc.buildout.configparser.parse(StringIO.StringIO(
    ...     text), 'test'))
    {'foo': {'bar': '', 'baz': 'a\n  b\n\nc'}}

The value of bar is ``''``, and the value of baz is ``'a\n  b\n\nc'``.

Lines starting with '#' or ';' characters are comments.  Comments can
also be placed after the closing square bracket (']') in a section header.

Buildout configuration data are Python strings, which are bytes in
Python 2 and unicode in Python 3.

Sections and options within sections may be repeated.  Multiple
occurrences of of a section are treated as if they were concatenated.
The last option value for a given name in a section overrides previous
values.

In addition top the syntactic details above:

- option names are case sensitive

- option values can use a substitution syntax, described below, to
  refer to option values in specific sections.

- option values can be appended or removed using the - and +
  operators.

Annotated sections
------------------

When used with the `annotate` command, buildout displays annotated sections.
All sections are displayed, sorted alphabetically. For each section,
all key-value pairs are displayed, sorted alphabetically, along with
the origin of the value (file name or COMPUTED_VALUE, DEFAULT_VALUE,
COMMAND_LINE_VALUE).

    >>> print_(system(buildout+ ' annotate'), end='')
    ... # doctest: +ELLIPSIS +NORMALIZE_WHITESPACE
    <BLANKLINE>
    Annotated sections
    ==================
    <BLANKLINE>
    [buildout]
    allow-hosts= *
        DEFAULT_VALUE
    allow-picked-versions= true
        DEFAULT_VALUE
    bin-directory= bin
        DEFAULT_VALUE
    develop= recipes
        /sample-buildout/buildout.cfg
    develop-eggs-directory= develop-eggs
        DEFAULT_VALUE
    directory= /sample-buildout
        COMPUTED_VALUE
    eggs-directory= /sample-buildout/eggs
        DEFAULT_VALUE
    executable= ...
        DEFAULT_VALUE
    find-links=
        DEFAULT_VALUE
    install-from-cache= false
        DEFAULT_VALUE
    installed= .installed.cfg
        DEFAULT_VALUE
    log-format=
        DEFAULT_VALUE
    log-level= INFO
        DEFAULT_VALUE
    newest= true
        DEFAULT_VALUE
    offline= false
        DEFAULT_VALUE
    parts= data-dir
        /sample-buildout/buildout.cfg
    parts-directory= parts
        DEFAULT_VALUE
    prefer-final= true
        DEFAULT_VALUE
    python= buildout
        DEFAULT_VALUE
    show-picked-versions= false
        DEFAULT_VALUE
    socket-timeout=
        DEFAULT_VALUE
    update-versions-file=
        DEFAULT_VALUE
    use-dependency-links= true
        DEFAULT_VALUE
    versions= versions
        DEFAULT_VALUE
    <BLANKLINE>
    [data-dir]
    path= foo bins
        /sample-buildout/buildout.cfg
    recipe= recipes:mkdir
        /sample-buildout/buildout.cfg
    <BLANKLINE>
    [versions]
    zc.buildout= >=1.99
        DEFAULT_VALUE
    zc.recipe.egg= >=1.99
        DEFAULT_VALUE
    <BLANKLINE>

Variable substitutions
----------------------

Buildout configuration files support variable substitution.
To illustrate this, we'll create an debug recipe to
allow us to see interactions with the buildout:

    >>> write(sample_buildout, 'recipes', 'debug.py',
    ... """
    ... import sys
    ... class Debug:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         self.buildout = buildout
    ...         self.name = name
    ...         self.options = options
    ...
    ...     def install(self):
    ...         for option, value in sorted(self.options.items()):
    ...             sys.stdout.write('%s %s\\n' % (option, value))
    ...         return ()
    ...
    ...     update = install
    ... """)

This recipe doesn't actually create anything. The install method
doesn't return anything, because it didn't create any files or
directories.

We also have to update our setup script:

    >>> write(sample_buildout, 'recipes', 'setup.py',
    ... """
    ... from setuptools import setup
    ... entry_points = (
    ... '''
    ... [zc.buildout]
    ... mkdir = mkdir:Mkdir
    ... debug = debug:Debug
    ... ''')
    ... setup(name="recipes", entry_points=entry_points)
    ... """)

We've rearranged the script a bit to make the entry points easier to
edit.  In particular, entry points are now defined as a configuration
string, rather than a dictionary.

Let's update our configuration to provide variable substitution
examples:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir debug
    ... log-level = INFO
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... File-1 = ${data-dir:path}/file
    ... File-2 = ${debug:File-1}/log
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = mydata
    ... """)

We used a string-template substitution for File-1 and File-2.  This
type of substitution uses the string.Template syntax.  Names
substituted are qualified option names, consisting of a section name
and option name joined by a colon.

Now, if we run the buildout, we'll see the options with the values
substituted.

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling data-dir.
    Installing data-dir.
    data-dir: Creating directory mydata
    Installing debug.
    File-1 /sample-buildout/mydata/file
    File-2 /sample-buildout/mydata/file/log
    recipe recipes:debug

Note that the substitution of the data-dir path option reflects the
update to the option performed by the mkdir recipe.

It might seem surprising that mydata was created again.  This is
because we changed our recipes package by adding the debug module.
The buildout system didn't know if this module could effect the mkdir
recipe, so it assumed it could and reinstalled mydata.  If we rerun
the buildout:

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Updating data-dir.
    Updating debug.
    File-1 /sample-buildout/mydata/file
    File-2 /sample-buildout/mydata/file/log
    recipe recipes:debug

We can see that mydata was not recreated.

Note that, in this case, we didn't specify a log level, so
we didn't get output about what the buildout was doing.

Section and option names in variable substitutions are only allowed to
contain alphanumeric characters, hyphens, periods and spaces. This
restriction might be relaxed in future releases.

We can omit the section name in a variable substitution to refer to
the current section.  We can also use the special option,
_buildout_section_name_ to get the current section name.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir debug
    ... log-level = INFO
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... File-1 = ${data-dir:path}/file
    ... File-2 = ${:File-1}/log
    ... my_name = ${:_buildout_section_name_}
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = mydata
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Updating data-dir.
    Installing debug.
    File-1 /sample-buildout/mydata/file
    File-2 /sample-buildout/mydata/file/log
    my_name debug
    recipe recipes:debug

Automatic part selection and ordering
-------------------------------------

When a section with a recipe is referred to, either through variable
substitution or by an initializing recipe, the section is treated as a
part and added to the part list before the referencing part.  For
example, we can leave data-dir out of the parts list:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ... log-level = INFO
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... File-1 = ${data-dir:path}/file
    ... File-2 = ${debug:File-1}/log
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = mydata
    ... """)


It will still be treated as a part:

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Updating data-dir.
    Installing debug.
    File-1 /sample-buildout/mydata/file
    File-2 /sample-buildout/mydata/file/log
    recipe recipes:debug

    >>> cat('.installed.cfg') # doctest: +ELLIPSIS
    [buildout]
    installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
    parts = data-dir debug
    ...

Note that the data-dir part is included *before* the debug part,
because the debug part refers to the data-dir part.  Even if we list
the data-dir part after the debug part, it will be included before:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug data-dir
    ... log-level = INFO
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... File-1 = ${data-dir:path}/file
    ... File-2 = ${debug:File-1}/log
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = mydata
    ... """)


It will still be treated as a part:

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Updating data-dir.
    Updating debug.
    File-1 /sample-buildout/mydata/file
    File-2 /sample-buildout/mydata/file/log
    recipe recipes:debug

    >>> cat('.installed.cfg') # doctest: +ELLIPSIS
    [buildout]
    installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
    parts = data-dir debug
    ...

Extending sections (macros)
---------------------------

A section (other than the buildout section) can extend one or more
other sections using the ``<`` option.  Options from the referenced
sections are copied to the referring section *before* variable
substitution.  This, together with the ability to refer to variables
of the current section allows sections to be used as macros.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = myfiles
    ... log-level = INFO
    ...
    ... [debug]
    ... recipe = recipes:debug
    ...
    ... [with_file1]
    ... <= debug
    ... file1 = ${:path}/file1
    ... color = red
    ...
    ... [with_file2]
    ... <= debug
    ... file2 = ${:path}/file2
    ... color = blue
    ...
    ... [myfiles]
    ... <= with_file1
    ...    with_file2
    ... path = mydata
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Uninstalling data-dir.
    Installing myfiles.
    color blue
    file1 mydata/file1
    file2 mydata/file2
    path mydata
    recipe recipes:debug

In this example, the debug, with_file1 and with_file2 sections act as
macros. In particular, the variable substitutions are performed
relative to the myfiles section.

Conditional sections
--------------------

Sometimes, you need different configuration in different environments
(different operating systems, or different versions of Python).  To
make this easier, you can define environment-specific options by
providing conditional sections::

    [ctl]
    suffix =

    [ctl:windows]
    suffix = .bat

.. -> conf

    >>> import zc.buildout.configparser
    >>> zc.buildout.configparser.parse(
    ...     StringIO.StringIO(conf), 'test', lambda : dict(windows=True))
    {'ctl': {'suffix': '.bat'}}
    >>> zc.buildout.configparser.parse(
    ...     StringIO.StringIO(conf), 'test', lambda : dict(windows=False))
    {'ctl': {'suffix': ''}}

In this tiny example, we've defined a ``ctl:suffix`` option that's
``.bat`` on Windows and an empty string elsewhere.

A conditional section has a colon and then a Python expression after
the name.  If the Python expression result is true, the section
options from the section are included.  If the value is false, the
section is ignored.

Some things to note:

- If there is no exception, then options from the section are
  included.

- Sections and options can be repeated.  If an option is repeated, the
  last value is used. In the example above, on Windows, the second
  ``suffix`` option overrides the first.  If the order of the sections
  was reversed, the conditional section would have no effect.

In addition to the normal built-ins, the expression has access to
global variable that make common cases short and description as shown
above:

sys
  the ``sys`` module

os
  the ``os`` module

platform
  the ``platform`` module

re
  The ``re`` module

python2
  We're running Python 2

python3
  We're running Python 3

python26
  We're running Python 2.6

python27
  We're running Python 2.7

python32
  We're running Python 3.2

python33
  We're running Python 3.3

sys_version
  ``sys.version.lower()``

pypy
  We're running PyPy

jython
  We're running Jython

iron
  We're running Iron Python

cpython
  We're not running PyPy, Jython, or Iron Python

sys_platform
  ``str(sys.platform).lower()``

linux
  We're running on linux

windows
  We're running on Windows

cygwin
  We're running on cygwin

solaris
  We're running on solaris

macosx
  We're running on Mac OS X

posix
  We're running on a POSIX-compatible system

bits32
  We're running on a 32-bit system.

bits64
  We're running on a 64-bit system.

little_endian
  We're running on a little-endian system

big_endian
  We're running on a little-endian system

Expressions must not contain either the ``#`` or the ``;`` character.


Adding and removing options
---------------------------

We can append and remove values to an option by using the + and -
operators.

This is illustrated below; first we define a base configuration.

    >>> write(sample_buildout, 'base.cfg',
    ... """
    ... [buildout]
    ... parts = part1 part2 part3
    ...
    ... [part1]
    ... recipe =
    ... option = a1 a2
    ...
    ... [part2]
    ... recipe =
    ... option = b1 b2 b3 b4
    ...
    ... [part3]
    ... recipe =
    ... option = c1 c2
    ...
    ... [part4]
    ... recipe =
    ... option = d2
    ...     d3
    ...     d5
    ...
    ... """)

Extending this configuration, we can "adjust" the values set in the
base configuration file.

    >>> write(sample_buildout, 'extension1.cfg',
    ... """
    ... [buildout]
    ... extends = base.cfg
    ...
    ... # appending values
    ... [part1]
    ... option += a3 a4
    ...
    ... # removing values
    ... [part2]
    ... option -= b1 b2
    ...
    ... # alt. spelling
    ... [part3]
    ... option+=c3 c4 c5
    ...
    ... # combining both adding and removing
    ... [part4]
    ... option += d1
    ...      d4
    ... option -= d5
    ...
    ... # normal assignment
    ... [part5]
    ... option = h1 h2
    ...
    ... """)

An additional extension.

    >>> write(sample_buildout, 'extension2.cfg',
    ... """
    ... [buildout]
    ... extends = extension1.cfg
    ...
    ... # appending values
    ... [part1]
    ... option += a5
    ...
    ... # removing values
    ... [part2]
    ... option -= b1 b2 b3
    ...
    ... """)

To verify that the options are adjusted correctly, we'll set up an
extension that prints out the options.

    >>> mkdir(sample_buildout, 'demo')
    >>> write(sample_buildout, 'demo', 'demo.py',
    ... """
    ... import sys
    ... def ext(buildout):
    ...     sys.stdout.write(str(
    ...         [part['option'] for name, part in sorted(buildout.items())
    ...          if name.startswith('part')])+'\\n')
    ... """)

    >>> write(sample_buildout, 'demo', 'setup.py',
    ... """
    ... from setuptools import setup
    ...
    ... setup(
    ...     name="demo",
    ...     entry_points={'zc.buildout.extension': ['ext = demo:ext']},
    ...     )
    ... """)

Set up a buildout configuration for this extension.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = demo
    ... parts =
    ... """)

    >>> os.chdir(sample_buildout)
    >>> print_(system(os.path.join(sample_buildout, 'bin', 'buildout')), end='')
    ... # doctest: +ELLIPSIS
    Develop: '/sample-buildout/demo'...

Verify option values.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = demo
    ... extensions = demo
    ... extends = extension2.cfg
    ... """)

    >>> print_(system(os.path.join('bin', 'buildout')), end='')
    ['a1 a2/na3 a4/na5', 'b1 b2 b3 b4', 'c1 c2/nc3 c4 c5', 'd2/nd3/nd1/nd4', 'h1 h2']
    Develop: '/sample-buildout/demo'

Annotated sections output shows which files are responsible for which
operations.

    >>> print_(system(os.path.join('bin', 'buildout') + ' annotate'), end='')
    ... # doctest: +ELLIPSIS +NORMALIZE_WHITESPACE
    <BLANKLINE>
    Annotated sections
    ==================
    ...
    <BLANKLINE>
    [part1]
    option= a1 a2
    a3 a4
    a5
        /sample-buildout/base.cfg
    +=  /sample-buildout/extension1.cfg
    +=  /sample-buildout/extension2.cfg
    recipe=
        /sample-buildout/base.cfg
    <BLANKLINE>
    [part2]
    option= b1 b2 b3 b4
        /sample-buildout/base.cfg
    -=  /sample-buildout/extension1.cfg
    -=  /sample-buildout/extension2.cfg
    recipe=
        /sample-buildout/base.cfg
    <BLANKLINE>
    [part3]
    option= c1 c2
    c3 c4 c5
        /sample-buildout/base.cfg
    +=  /sample-buildout/extension1.cfg
    recipe=
        /sample-buildout/base.cfg
    <BLANKLINE>
    [part4]
    option= d2
    d3
    d1
    d4
        /sample-buildout/base.cfg
    +=  /sample-buildout/extension1.cfg
    -=  /sample-buildout/extension1.cfg
    recipe=
        /sample-buildout/base.cfg
    <BLANKLINE>
    [part5]
    option= h1 h2
        /sample-buildout/extension1.cfg
    [versions]
    zc.buildout= >=1.99
        DEFAULT_VALUE
    zc.recipe.egg= >=1.99
        DEFAULT_VALUE
    <BLANKLINE>

Cleanup.

    >>> os.remove(os.path.join(sample_buildout, 'base.cfg'))
    >>> os.remove(os.path.join(sample_buildout, 'extension1.cfg'))
    >>> os.remove(os.path.join(sample_buildout, 'extension2.cfg'))

Multiple configuration files
----------------------------

A configuration file can "extend" another configuration file.
Options are read from the other configuration file if they aren't
already defined by your configuration file.

The configuration files your file extends can extend
other configuration files.  The same file may be
used more than once although, of course, cycles aren't allowed.

To see how this works, we use an example:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... extends = base.cfg
    ...
    ... [debug]
    ... op = buildout
    ... """)

    >>> write(sample_buildout, 'base.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... op = base
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Installing debug.
    op buildout
    recipe recipes:debug

The example is pretty trivial, but the pattern it illustrates is
pretty common.  In a more practical example, the base buildout might
represent a product and the extending buildout might be a
customization.

Here is a more elaborate example.

    >>> other = tmpdir('other')

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... extends = b1.cfg b2.cfg %(b3)s
    ...
    ... [debug]
    ... op = buildout
    ... """ % dict(b3=os.path.join(other, 'b3.cfg')))

    >>> write(sample_buildout, 'b1.cfg',
    ... """
    ... [buildout]
    ... extends = base.cfg
    ...
    ... [debug]
    ... op1 = b1 1
    ... op2 = b1 2
    ... """)

    >>> write(sample_buildout, 'b2.cfg',
    ... """
    ... [buildout]
    ... extends = base.cfg
    ...
    ... [debug]
    ... op2 = b2 2
    ... op3 = b2 3
    ... """)

    >>> write(other, 'b3.cfg',
    ... """
    ... [buildout]
    ... extends = b3base.cfg
    ...
    ... [debug]
    ... op4 = b3 4
    ... """)

    >>> write(other, 'b3base.cfg',
    ... """
    ... [debug]
    ... op5 = b3base 5
    ... """)

    >>> write(sample_buildout, 'base.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... name = base
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    name base
    op buildout
    op1 b1 1
    op2 b2 2
    op3 b2 3
    op4 b3 4
    op5 b3base 5
    recipe recipes:debug

There are several things to note about this example:

- We can name multiple files in an extends option.

- We can reference files recursively.

- Relative file names in extended options are interpreted relative to
  the directory containing the referencing configuration file.

Loading Configuration from URLs
-------------------------------

Configuration files can be loaded from URLs.  To see how this works,
we'll set up a web server with some configuration files.

    >>> server_data = tmpdir('server_data')

    >>> write(server_data, "r1.cfg",
    ... """
    ... [debug]
    ... op1 = r1 1
    ... op2 = r1 2
    ... """)

    >>> write(server_data, "r2.cfg",
    ... """
    ... [buildout]
    ... extends = r1.cfg
    ...
    ... [debug]
    ... op2 = r2 2
    ... op3 = r2 3
    ... """)

    >>> server_url = start_server(server_data)

    >>> write('client.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ... extends = %(url)s/r2.cfg
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... name = base
    ... """ % dict(url=server_url))


    >>> print_(system(buildout+ ' -c client.cfg'), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    name base
    op1 r1 1
    op2 r2 2
    op3 r2 3
    recipe recipes:debug

Here we specified a URL for the file we extended.  The file we
downloaded, itself referred to a file on the server using a relative
URL reference.  Relative references are interpreted relative to the
base URL when they appear in configuration files loaded via URL.

We can also specify a URL as the configuration file to be used by a
buildout.

    >>> os.remove('client.cfg')
    >>> write(server_data, 'remote.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ... extends = r2.cfg
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... name = remote
    ... """)

    >>> print_(system(buildout + ' -c ' + server_url + '/remote.cfg'), end='')
    While:
      Initializing.
    Error: Missing option: buildout:directory

Normally, the buildout directory defaults to directory
containing a configuration file.  This won't work for configuration
files loaded from URLs.  In this case, the buildout directory would
normally be defined on the command line:

    >>> print_(system(buildout
    ...              + ' -c ' + server_url + '/remote.cfg'
    ...              + ' buildout:directory=' + sample_buildout
    ...              ), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    name remote
    op1 r1 1
    op2 r2 2
    op3 r2 3
    recipe recipes:debug

User defaults
-------------

If the file $HOME/.buildout/default.cfg, exists, it is read before
reading the configuration file.  ($HOME is the value of the HOME
environment variable. The '/' is replaced by the operating system file
delimiter.)

    >>> old_home = os.environ['HOME']
    >>> home = tmpdir('home')
    >>> mkdir(home, '.buildout')
    >>> write(home, '.buildout', 'default.cfg',
    ... """
    ... [debug]
    ... op1 = 1
    ... op7 = 7
    ... """)

    >>> os.environ['HOME'] = home
    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    name base
    op buildout
    op1 b1 1
    op2 b2 2
    op3 b2 3
    op4 b3 4
    op5 b3base 5
    op7 7
    recipe recipes:debug

A buildout command-line argument, -U, can be used to suppress reading
user defaults:

    >>> print_(system(buildout + ' -U'), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    name base
    op buildout
    op1 b1 1
    op2 b2 2
    op3 b2 3
    op4 b3 4
    op5 b3base 5
    recipe recipes:debug

If the environment variable BUILDOUT_HOME is non-empty, that is used to
locate default.cfg instead of looking in ~/.buildout/.  Let's set up a
configuration file in an alternate directory and verify that we get the
appropriate set of defaults:

    >>> alterhome = tmpdir('alterhome')
    >>> write(alterhome, 'default.cfg',
    ... """
    ... [debug]
    ... op1 = 1'
    ... op7 = 7'
    ... op8 = eight!
    ... """)

    >>> os.environ['BUILDOUT_HOME'] = alterhome
    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    name base
    op buildout
    op1 b1 1
    op2 b2 2
    op3 b2 3
    op4 b3 4
    op5 b3base 5
    op7 7'
    op8 eight!
    recipe recipes:debug

The -U argument still suppresses reading of the default.cfg file from
BUILDOUT_HOME:

    >>> print_(system(buildout + ' -U'), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    name base
    op buildout
    op1 b1 1
    op2 b2 2
    op3 b2 3
    op4 b3 4
    op5 b3base 5
    recipe recipes:debug

    >>> os.environ['HOME'] = old_home
    >>> del os.environ['BUILDOUT_HOME']

Log level
---------

We can control the level of logging by specifying a log level in out
configuration file.  For example, so suppress info messages, we can
set the logging level to WARNING

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... log-level = WARNING
    ... extends = b1.cfg b2.cfg
    ... """)

    >>> print_(system(buildout), end='')
    name base
    op1 b1 1
    op2 b2 2
    op3 b2 3
    recipe recipes:debug

Socket timeout
--------------

The timeout of the connections to egg and configuration servers can be
configured in the buildout section. Its value is configured in seconds.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... socket-timeout = 5
    ... develop = recipes
    ... parts = debug
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... op = timeout
    ... """)

    >>> print_(system(buildout), end='')
    Setting socket time out to 5 seconds.
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    op timeout
    recipe recipes:debug

If the socket-timeout is not numeric, a warning is issued and the default
timeout of the Python socket module is used.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... socket-timeout = 5s
    ... develop = recipes
    ... parts = debug
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... op = timeout
    ... """)

    >>> print_(system(buildout), end='')
    Default socket timeout is used !
    Value in configuration is not numeric: [5s].
    <BLANKLINE>
    Develop: '/sample-buildout/recipes'
    Updating debug.
    op timeout
    recipe recipes:debug

Uninstall recipes
-----------------

As we've seen, when parts are installed, buildout keeps track of files
and directories that they create. When the parts are uninstalled these
files and directories are deleted.

Sometimes more clean up is needed. For example, a recipe might add a
system service by calling chkconfig --add during installation. Later
during uninstallation, chkconfig --del will need to be called to
remove the system service.

In order to deal with these uninstallation issues, you can register
uninstall recipes. Uninstall recipes are registered using the
'zc.buildout.uninstall' entry point. Parts specify uninstall recipes
using the 'uninstall' option.

In comparison to regular recipes, uninstall recipes are much
simpler. They are simply callable objects that accept the name of the
part to be uninstalled and the part's options dictionary. Uninstall
recipes don't have access to the part itself since it maybe not be
able to be instantiated at uninstallation time.

Here's a recipe that simulates installation of a system service, along
with an uninstall recipe that simulates removing the service.

    >>> write(sample_buildout, 'recipes', 'service.py',
    ... """
    ... import sys
    ... class Service:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         self.buildout = buildout
    ...         self.name = name
    ...         self.options = options
    ...
    ...     def install(self):
    ...         sys.stdout.write("chkconfig --add %s\\n"
    ...                          % self.options['script'])
    ...         return ()
    ...
    ...     def update(self):
    ...         pass
    ...
    ...
    ... def uninstall_service(name, options):
    ...     sys.stdout.write("chkconfig --del %s\\n" % options['script'])
    ... """)

To use these recipes we must register them using entry points. Make
sure to use the same name for the recipe and uninstall recipe. This is
required to let buildout know which uninstall recipe goes with which
recipe.

    >>> write(sample_buildout, 'recipes', 'setup.py',
    ... """
    ... from setuptools import setup
    ... entry_points = (
    ... '''
    ... [zc.buildout]
    ... mkdir = mkdir:Mkdir
    ... debug = debug:Debug
    ... service = service:Service
    ...
    ... [zc.buildout.uninstall]
    ... service = service:uninstall_service
    ... ''')
    ... setup(name="recipes", entry_points=entry_points)
    ... """)

Here's how these recipes could be used in a buildout:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = service
    ...
    ... [service]
    ... recipe = recipes:service
    ... script = /path/to/script
    ... """)

When the buildout is run the service will be installed

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing service.
    chkconfig --add /path/to/script

The service has been installed. If the buildout is run again with no
changes, the service shouldn't be changed.

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Updating service.

Now we change the service part to trigger uninstallation and
re-installation.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = service
    ...
    ... [service]
    ... recipe = recipes:service
    ... script = /path/to/a/different/script
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling service.
    Running uninstall recipe.
    chkconfig --del /path/to/script
    Installing service.
    chkconfig --add /path/to/a/different/script

Now we remove the service part, and add another part.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling service.
    Running uninstall recipe.
    chkconfig --del /path/to/a/different/script
    Installing debug.
    recipe recipes:debug

Uninstall recipes don't have to take care of removing all the files
and directories created by the part. This is still done automatically,
following the execution of the uninstall recipe. An upshot is that an
uninstallation recipe can access files and directories created by a
recipe before they are deleted.

For example, here's an uninstallation recipe that simulates backing up
a directory before it is deleted. It is designed to work with the
mkdir recipe introduced earlier.

    >>> write(sample_buildout, 'recipes', 'backup.py',
    ... """
    ... import os, sys
    ... def backup_directory(name, options):
    ...     path = options['path']
    ...     size = len(os.listdir(path))
    ...     sys.stdout.write("backing up directory %s of size %s\\n"
    ...                      % (path, size))
    ... """)

It must be registered with the zc.buildout.uninstall entry
point. Notice how it is given the name 'mkdir' to associate it with
the mkdir recipe.

    >>> write(sample_buildout, 'recipes', 'setup.py',
    ... """
    ... from setuptools import setup
    ... entry_points = (
    ... '''
    ... [zc.buildout]
    ... mkdir = mkdir:Mkdir
    ... debug = debug:Debug
    ... service = service:Service
    ...
    ... [zc.buildout.uninstall]
    ... uninstall_service = service:uninstall_service
    ... mkdir = backup:backup_directory
    ... ''')
    ... setup(name="recipes", entry_points=entry_points)
    ... """)

Now we can use it with a mkdir part.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = dir debug
    ...
    ... [dir]
    ... recipe = recipes:mkdir
    ... path = my_directory
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... """)

Run the buildout to install the part.

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing dir.
    dir: Creating directory my_directory
    Installing debug.
    recipe recipes:debug

Now we remove the part from the configuration file.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... """)

When the buildout is run the part is removed, and the uninstall recipe
is run before the directory is deleted.

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling dir.
    Running uninstall recipe.
    backing up directory /sample-buildout/my_directory of size 0
    Updating debug.
    recipe recipes:debug

Now we will return the registration to normal for the benefit of the
rest of the examples.

    >>> write(sample_buildout, 'recipes', 'setup.py',
    ... """
    ... from setuptools import setup
    ... entry_points = (
    ... '''
    ... [zc.buildout]
    ... mkdir = mkdir:Mkdir
    ... debug = debug:Debug
    ... ''')
    ... setup(name="recipes", entry_points=entry_points)
    ... """)


Command-line usage
------------------

A number of arguments can be given on the buildout command line.  The
command usage is::

  buildout [options and assignments] [command [command arguments]]

The following options are supported:

-h (or --help)
    Print basic usage information.  If this option is used, then all
    other options are ignored.

-c filename
    The -c option can be used to specify a configuration file, rather than
    buildout.cfg in the current directory.


-t socket_timeout

   Specify the socket timeout in seconds.

-v
    Increment the verbosity by 10.  The verbosity is used to adjust
    the logging level.  The verbosity is subtracted from the numeric
    value of the log-level option specified in the configuration file.

-q
    Decrement the verbosity by 10.

-U
    Don't read user-default configuration.

-o
    Run in off-line mode.  This is equivalent to the assignment
    buildout:offline=true.

-O
    Run in non-off-line mode.  This is equivalent to the assignment
    buildout:offline=false.  This is the default buildout mode.  The
    -O option would normally be used to override a true offline
    setting in a configuration file.

-n
    Run in newest mode.  This is equivalent to the assignment
    buildout:newest=true.  With this setting, which is the default,
    buildout will try to find the newest versions of distributions
    available that satisfy its requirements.

-N
    Run in non-newest mode.  This is equivalent to the assignment
    buildout:newest=false.  With this setting, buildout will not seek
    new distributions if installed distributions satisfy it's
    requirements.

Assignments are of the form::

  section_name:option_name=value

Or::

  option_name=value

which is equivalent to::

  buildout:option_name=value

Options and assignments can be given in any order.

Here's an example:

    >>> write(sample_buildout, 'other.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ... installed = .other.cfg
    ... log-level = WARNING
    ...
    ... [debug]
    ... name = other
    ... recipe = recipes:debug
    ... """)

Note that we used the installed buildout option to specify an
alternate file to store information about installed parts.

    >>> print_(system(buildout+' -c other.cfg debug:op1=foo -v'), end='')
    Develop: '/sample-buildout/recipes'
    Installing debug.
    name other
    op1 foo
    recipe recipes:debug

Here we used the -c option to specify an alternate configuration file,
and the -v option to increase the level of logging from the default,
WARNING.

Options can also be combined in the usual Unix way, as in:

    >>> print_(system(buildout+' -vcother.cfg debug:op1=foo'), end='')
    Develop: '/sample-buildout/recipes'
    Updating debug.
    name other
    op1 foo
    recipe recipes:debug

Here we combined the -v and -c options with the configuration file
name.  Note that the -c option has to be last, because it takes an
argument.

    >>> os.remove(os.path.join(sample_buildout, 'other.cfg'))
    >>> os.remove(os.path.join(sample_buildout, '.other.cfg'))

The most commonly used command is 'install' and it takes a list of
parts to install. if any parts are specified, only those parts are
installed.  To illustrate this, we'll update our configuration and run
the buildout in the usual way:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug d1 d2 d3
    ...
    ... [d1]
    ... recipe = recipes:mkdir
    ... path = d1
    ...
    ... [d2]
    ... recipe = recipes:mkdir
    ... path = d2
    ...
    ... [d3]
    ... recipe = recipes:mkdir
    ... path = d3
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... """)

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling debug.
    Installing debug.
    recipe recipes:debug
    Installing d1.
    d1: Creating directory d1
    Installing d2.
    d2: Creating directory d2
    Installing d3.
    d3: Creating directory d3

    >>> ls(sample_buildout)
    -  .installed.cfg
    -  b1.cfg
    -  b2.cfg
    -  base.cfg
    d  bin
    -  buildout.cfg
    d  d1
    d  d2
    d  d3
    d  demo
    d  develop-eggs
    d  eggs
    d  parts
    d  recipes

    >>> cat(sample_buildout, '.installed.cfg')
    ... # doctest: +NORMALIZE_WHITESPACE
    [buildout]
    installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
    parts = debug d1 d2 d3
    <BLANKLINE>
    [debug]
    __buildout_installed__ =
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    recipe = recipes:debug
    <BLANKLINE>
    [d1]
    __buildout_installed__ = /sample-buildout/d1
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    path = /sample-buildout/d1
    recipe = recipes:mkdir
    <BLANKLINE>
    [d2]
    __buildout_installed__ = /sample-buildout/d2
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    path = /sample-buildout/d2
    recipe = recipes:mkdir
    <BLANKLINE>
    [d3]
    __buildout_installed__ = /sample-buildout/d3
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    path = /sample-buildout/d3
    recipe = recipes:mkdir

Now we'll update our configuration file:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug d2 d3 d4
    ...
    ... [d2]
    ... recipe = recipes:mkdir
    ... path = data2
    ...
    ... [d3]
    ... recipe = recipes:mkdir
    ... path = data3
    ...
    ... [d4]
    ... recipe = recipes:mkdir
    ... path = ${d2:path}-extra
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... x = 1
    ... """)

and run the buildout specifying just d3 and d4:

    >>> print_(system(buildout+' install d3 d4'), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling d3.
    Installing d3.
    d3: Creating directory data3
    Installing d4.
    d4: Creating directory data2-extra

    >>> ls(sample_buildout)
    -  .installed.cfg
    -  b1.cfg
    -  b2.cfg
    -  base.cfg
    d  bin
    -  buildout.cfg
    d  d1
    d  d2
    d  data2-extra
    d  data3
    d  demo
    d  develop-eggs
    d  eggs
    d  parts
    d  recipes

Only the d3 and d4 recipes ran.  d3 was removed and data3 and data2-extra
were created.

The .installed.cfg is only updated for the recipes that ran:

    >>> cat(sample_buildout, '.installed.cfg')
    ... # doctest: +NORMALIZE_WHITESPACE
    [buildout]
    installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
    parts = debug d1 d2 d3 d4
    <BLANKLINE>
    [debug]
    __buildout_installed__ =
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    recipe = recipes:debug
    <BLANKLINE>
    [d1]
    __buildout_installed__ = /sample-buildout/d1
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    path = /sample-buildout/d1
    recipe = recipes:mkdir
    <BLANKLINE>
    [d2]
    __buildout_installed__ = /sample-buildout/d2
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    path = /sample-buildout/d2
    recipe = recipes:mkdir
    <BLANKLINE>
    [d3]
    __buildout_installed__ = /sample-buildout/data3
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    path = /sample-buildout/data3
    recipe = recipes:mkdir
    <BLANKLINE>
    [d4]
    __buildout_installed__ = /sample-buildout/data2-extra
    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
    path = /sample-buildout/data2-extra
    recipe = recipes:mkdir

Note that the installed data for debug, d1, and d2 haven't changed,
because we didn't install those parts and that the d1 and d2
directories are still there.

Now, if we run the buildout without the install command:

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Uninstalling d2.
    Uninstalling d1.
    Uninstalling debug.
    Installing debug.
    recipe recipes:debug
    x 1
    Installing d2.
    d2: Creating directory data2
    Updating d3.
    Updating d4.

We see the output of the debug recipe and that data2 was created.  We
also see that d1 and d2 have gone away:

    >>> ls(sample_buildout)
    -  .installed.cfg
    -  b1.cfg
    -  b2.cfg
    -  base.cfg
    d  bin
    -  buildout.cfg
    d  data2
    d  data2-extra
    d  data3
    d  demo
    d  develop-eggs
    d  eggs
    d  parts
    d  recipes

Alternate directory and file locations
--------------------------------------

The buildout normally puts the bin, eggs, and parts directories in the
directory in the directory containing the configuration file. You can
provide alternate locations, and even names for these directories.

    >>> alt = tmpdir('sample-alt')

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts =
    ... develop-eggs-directory = %(developbasket)s
    ... eggs-directory = %(basket)s
    ... bin-directory = %(scripts)s
    ... parts-directory = %(work)s
    ... """ % dict(
    ...    developbasket = os.path.join(alt, 'developbasket'),
    ...    basket = os.path.join(alt, 'basket'),
    ...    scripts = os.path.join(alt, 'scripts'),
    ...    work = os.path.join(alt, 'work'),
    ... ))

    >>> print_(system(buildout), end='')
    Creating directory '/sample-alt/basket'.
    Creating directory '/sample-alt/scripts'.
    Creating directory '/sample-alt/work'.
    Creating directory '/sample-alt/developbasket'.
    Develop: '/sample-buildout/recipes'
    Uninstalling d4.
    Uninstalling d3.
    Uninstalling d2.
    Uninstalling debug.

    >>> ls(alt)
    d  basket
    d  developbasket
    d  scripts
    d  work

    >>> ls(alt, 'developbasket')
    -  recipes.egg-link

You can also specify an alternate buildout directory:

    >>> rmdir(alt)
    >>> alt = tmpdir('sample-alt')

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... directory = %(alt)s
    ... develop = %(recipes)s
    ... parts =
    ... """ % dict(
    ...    alt=alt,
    ...    recipes=os.path.join(sample_buildout, 'recipes'),
    ...    ))

    >>> print_(system(buildout), end='')
    Creating directory '/sample-alt/eggs'.
    Creating directory '/sample-alt/bin'.
    Creating directory '/sample-alt/parts'.
    Creating directory '/sample-alt/develop-eggs'.
    Develop: '/sample-buildout/recipes'

    >>> ls(alt)
    -  .installed.cfg
    d  bin
    d  develop-eggs
    d  eggs
    d  parts

    >>> ls(alt, 'develop-eggs')
    -  recipes.egg-link

Logging control
---------------

Three buildout options are used to control logging:

log-level
   specifies the log level

verbosity
   adjusts the log level

log-format
   allows an alternate logging for mat to be specified

We've already seen the log level and verbosity.  Let's look at an example
of changing the format:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts =
    ... log-level = 25
    ... verbosity = 5
    ... log-format = %(levelname)s %(message)s
    ... """)

Here, we've changed the format to include the log-level name, rather
than the logger name.

We've also illustrated, with a contrived example, that the log level
can be a numeric value and that the verbosity can be specified in the
configuration file.  Because the verbosity is subtracted from the log
level, we get a final log level of 20, which is the INFO level.

    >>> print_(system(buildout), end='')
    INFO Develop: '/sample-buildout/recipes'

Predefined buildout options
---------------------------

Buildouts have a number of predefined options that recipes can use
and that users can override in their configuration files.  To see
these, we'll run a minimal buildout configuration with a debug logging
level.  One of the features of debug logging is that the configuration
database is shown.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... parts =
    ... """)

    >>> print_(system(buildout+' -vv'), end='') # doctest: +NORMALIZE_WHITESPACE
    Installing 'zc.buildout', 'setuptools'.
    We have a develop egg: zc.buildout 1.0.0.
    We have the best distribution that satisfies 'setuptools'.
    Picked: setuptools = 0.7
    <BLANKLINE>
    Configuration data:
    [buildout]
    allow-hosts = *
    allow-picked-versions = true
    bin-directory = /sample-buildout/bin
    develop-eggs-directory = /sample-buildout/develop-eggs
    directory = /sample-buildout
    eggs-directory = /sample-buildout/eggs
    executable = python
    find-links =
    install-from-cache = false
    installed = /sample-buildout/.installed.cfg
    log-format =
    log-level = INFO
    newest = true
    offline = false
    parts =
    parts-directory = /sample-buildout/parts
    prefer-final = true
    python = buildout
    show-picked-versions = false
    socket-timeout =
    update-versions-file =
    use-dependency-links = true
    verbosity = 20
    versions = versions
    [versions]
    zc.buildout = >=1.99
    zc.recipe.egg = >=1.99
    <BLANKLINE>

All of these options can be overridden by configuration files or by
command-line assignments.  We've discussed most of these options
already, but let's review them and touch on some we haven't discussed:

allow-hosts
    On some environments the links visited by `zc.buildout` can be forbidden by
    paranoid firewalls. These URLs might be in the chain of links visited by
    `zc.buildout` as defined by buildout's `find-links` option, or as defined
    by various eggs in their `url`, `download_url`, `dependency_links` metadata.

    The fact that package_index works like a spider and might visit links and
    go to other locations makes this even harder.

    The `allow-hosts` option provides a way to prevent this, and
    works exactly like the one provided in `easy_install`.

    You can provide a list of allowed host, together with wildcards::

        [buildout]
        ...

        allow-hosts =
            *.python.org
            example.com

    All URLs that does not match these hosts will not be visited.

allow-picked-versions
    By default, the buildout will choose the best match for a given requirement
    if the requirement is not specified precisely (for instance, using the
    "versions" option.  This behavior corresponds to the
    "allow-picked-versions" being set to its default value, "true".  If
    "allow-picked-versions" is "false," instead of picking the best match,
    buildout will raise an error.  This helps enforce repeatability.

bin-directory
   The directory path where scripts are written.  This can be a
   relative path, which is interpreted relative to the directory
   option.

develop-eggs-directory
   The directory path where development egg links are created for software
   being created in the local project.  This can be a relative path,
   which is interpreted relative to the directory option.

directory
   The buildout directory.  This is the base for other buildout file
   and directory locations, when relative locations are used.

eggs-directory
   The directory path where downloaded eggs are put.  It is common to share
   this directory across buildouts. Eggs in this directory should
   *never* be modified.  This can be a relative path, which is
   interpreted relative to the directory option.

find-links
    You can specify more locations to search for distributions using the
    `find-links` option. All locations specified will be searched for
    distributions along with the package index as described before.

    Locations can be urls::

      [buildout]
      ...
      find-links = http://download.zope.org/distribution/

    They can also be directories on disk::

      [buildout]
      ...
      find-links = /some/path

    Finally, they can also be direct paths to distributions::

      [buildout]
      ...
      find-links = /some/path/someegg-1.0.0-py2.3.egg

    Any number of locations can be specified in the `find-links` option::

      [buildout]
      ...
      find-links =
          http://download.zope.org/distribution/
          /some/otherpath
          /some/path/someegg-1.0.0-py2.3.egg

install-from-cache
    A download cache can be used as the basis of application source releases.
    In an application source release, we want to distribute an application that
    can be built without making any network accesses.  In this case, we
    distribute a buildout with download cache and tell the buildout to install
    from the download cache only, without making network accesses.  The
    buildout install-from-cache option can be used to signal that packages
    should be installed only from the download cache.

installed
   The file path where information about the results of the previous
   buildout run is written.  This can be a relative path, which is
   interpreted relative to the directory option.  This file provides
   an inventory of installed parts with information needed to decide
   which if any parts need to be uninstalled.

log-format
   The format used for logging messages.

log-level
   The log level before verbosity adjustment

newest
    By default buildout and recipes will try to find the newest versions of
    distributions needed to satisfy requirements.  This can be very time
    consuming, especially when incrementally working on setting up a buildout
    or working on a recipe.  The buildout "newest" option can be used to to
    suppress this.  If the "newest" option is set to false, then new
    distributions won't be sought if an installed distribution meets
    requirements.  The "newest" option can also be set to false using the -N
    command-line option.  See also the "offline" option.

offline
    The "offline" option goes a bit further than the "newest" option.  If the
    buildout "offline" option is given a value of "true", the buildout and
    recipes that are aware of the option will avoid doing network access.  This
    is handy when running the buildout when not connected to the internet.  It
    also makes buildouts run much faster. This option is typically set using
    the buildout -o option.

parts
   A white space separated list of parts to be installed.

parts-directory
   A working directory that parts can used to store data.

prefer-final
    Currently, when searching for new releases, the newest available
    release is used.  This isn't usually ideal, as you may get a
    development release or alpha releases not ready to be widely used.
    You can request that final releases be preferred using the prefer
    final option in the buildout section::

      [buildout]
      ...
      prefer-final = true

    When the prefer-final option is set to true, then when searching for
    new releases, final releases are preferred.  If there are final
    releases that satisfy distribution requirements, then those releases
    are used even if newer non-final releases are available.  The buildout
    prefer-final option can be used to override this behavior.

    In buildout version 2, final releases will be preferred by default.
    You will then need to use a false value for prefer-final to get the
    newest releases.

use-dependency-links
    By default buildout will obey the setuptools dependency_links metadata
    when it looks for dependencies. This behavior can be controlled with
    the use-dependency-links buildout option::

      [buildout]
      ...
      use-dependency-links = false

    The option defaults to true. If you set it to false, then dependency
    links are only looked for in the locations specified by find-links.

verbosity
   A log-level adjustment.  Typically, this is set via the -q and -v
   command-line options.


Creating new buildouts and bootstrapping
----------------------------------------

If zc.buildout is installed, you can use it to create a new buildout
with it's own local copies of zc.buildout and setuptools and with
local buildout scripts.

    >>> sample_bootstrapped = tmpdir('sample-bootstrapped')

    >>> print_(system(buildout
    ...              +' -c'+os.path.join(sample_bootstrapped, 'setup.cfg')
    ...              +' init'), end='')
    Creating '/sample-bootstrapped/setup.cfg'.
    Creating directory '/sample-bootstrapped/eggs'.
    Creating directory '/sample-bootstrapped/bin'.
    Creating directory '/sample-bootstrapped/parts'.
    Creating directory '/sample-bootstrapped/develop-eggs'.
    Generated script '/sample-bootstrapped/bin/buildout'.

Note that a basic setup.cfg was created for us.  This is because we
provided an 'init' argument.  By default, the generated
``setup.cfg`` is as minimal as it could be:

    >>> cat(sample_bootstrapped, 'setup.cfg')
    [buildout]
    parts =

We also get other buildout artifacts:

    >>> ls(sample_bootstrapped)
    d  bin
    d  develop-eggs
    d  eggs
    d  parts
    -  setup.cfg

    >>> ls(sample_bootstrapped, 'bin')
    -  buildout

    >>> _ = (ls(sample_bootstrapped, 'eggs'),
    ...      ls(sample_bootstrapped, 'develop-eggs'))
    -  setuptools-0.7-py2.3.egg
    -  zc.buildout-1.0-py2.3.egg

(We list both the eggs and develop-eggs directories because the
buildout or setuptools egg could be installed in the develop-eggs
directory if the original buildout had develop eggs for either
buildout or setuptools.)

Note that the buildout script was installed but not run.  To run
the buildout, we'd have to run the installed buildout script.

If we have an existing buildout that already has a buildout.cfg, we'll
normally use the bootstrap command instead of init.  It will complain
if there isn't a configuration file:

    >>> sample_bootstrapped2 = tmpdir('sample-bootstrapped2')

    >>> print_(system(buildout
    ...              +' -c'+os.path.join(sample_bootstrapped2, 'setup.cfg')
    ...              +' bootstrap'), end='')
    While:
      Initializing.
    Error: Couldn't open /sample-bootstrapped2/setup.cfg

    >>> write(sample_bootstrapped2, 'setup.cfg',
    ... """
    ... [buildout]
    ... parts =
    ... """)

    >>> print_(system(buildout
    ...              +' -c'+os.path.join(sample_bootstrapped2, 'setup.cfg')
    ...              +' bootstrap'), end='')
    Creating directory '/sample-bootstrapped2/eggs'.
    Creating directory '/sample-bootstrapped2/bin'.
    Creating directory '/sample-bootstrapped2/parts'.
    Creating directory '/sample-bootstrapped2/develop-eggs'.
    Generated script '/sample-bootstrapped2/bin/buildout'.

Similarly, if there is a configuration file and we use the init
command, we'll get an error that the configuration file already
exists:

    >>> print_(system(buildout
    ...              +' -c'+os.path.join(sample_bootstrapped, 'setup.cfg')
    ...              +' init'), end='')
    While:
      Initializing.
    Error: '/sample-bootstrapped/setup.cfg' already exists.

Initial eggs
------------

When using the ``init`` command, you can specify distribution requirements
or paths to use:

    >>> cd(sample_bootstrapped)
    >>> remove('setup.cfg')
    >>> print_(system(buildout + ' -csetup.cfg init demo other ./src'), end='')
    Creating '/sample-bootstrapped/setup.cfg'.
    Creating directory '/sample-bootstrapped/develop-eggs'.
    Getting distribution for 'zc.recipe.egg>=2.0.0a3'.
    Got zc.recipe.egg
    Installing py.
    Getting distribution for 'demo'.
    Got demo 0.3.
    Getting distribution for 'other'.
    Got other 1.0.
    Getting distribution for 'demoneeded'.
    Got demoneeded 1.1.
    Generated script '/sample-bootstrapped/bin/demo'.
    Generated script '/sample-bootstrapped/bin/distutilsscript'.
    Generated interpreter '/sample-bootstrapped/bin/py'.

This causes a ``py`` part to be included that sets up a custom python
interpreter with the given requirements or paths:

    >>> cat('setup.cfg')
    [buildout]
    parts = py
    <BLANKLINE>
    [py]
    recipe = zc.recipe.egg
    interpreter = py
    eggs =
      demo
      other
    extra-paths =
      ./src

Passing requirements or paths causes the the buildout to be run as part
of initialization.  In the example above, we got a number of
distributions installed and 2 scripts generated.  The first, ``demo``,
was defined by the ``demo`` project. The second, ``py`` was defined by
the generated configuration.  It's a "custom interpreter" that behaves
like a standard Python interpreter, except that includes the specified
eggs and extra paths in it's Python path.

We specified a source directory that didn't exist. Buildout created it
for us:

    >>> ls('.')
    -  .installed.cfg
    d  bin
    d  develop-eggs
    d  eggs
    d  parts
    -  setup.cfg
    d  src

    >>> uncd()

.. Make sure it works if the dir is already there:

    >>> cd(sample_bootstrapped)
    >>> _ = system(buildout + ' -csetup.cfg buildout:parts=')
    >>> remove('setup.cfg')
    >>> print_(system(buildout + ' -csetup.cfg init demo other ./src'), end='')
    Creating '/sample-bootstrapped/setup.cfg'.
    Creating directory '/sample-bootstrapped/develop-eggs'.
    Installing py.
    Generated script '/sample-bootstrapped/bin/demo'.
    Generated script '/sample-bootstrapped/bin/distutilsscript'.
    Generated interpreter '/sample-bootstrapped/bin/py'.

.. cleanup

    >>> _ = system(buildout + ' -csetup.cfg buildout:parts=')
    >>> uncd()

Finding distributions
---------------------

By default, buildout searches the Python Package Index when looking
for distributions. You can, instead, specify your own index to search
using the `index` option::

  [buildout]
  ...
  index = http://index.example.com/

This index, or the default of http://pypi.python.org/simple/ if no
index is specified, will always be searched for distributions unless
running buildout with options that prevent searching for
distributions. The latest version of the distribution that meets the
requirements of the buildout will always be used.

You can also specify more locations to search for distributions using
the `find-links` option. See its description above.

Controlling the installation database
-------------------------------------

The buildout installed option is used to specify the file used to save
information on installed parts.  This option is initialized to
".installed.cfg", but it can be overridden in the configuration file
or on the command line:

    >>> write('buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = debug
    ...
    ... [debug]
    ... recipe = recipes:debug
    ... """)

    >>> print_(system(buildout+' buildout:installed=inst.cfg'), end='')
    Develop: '/sample-buildout/recipes'
    Installing debug.
    recipe recipes:debug

    >>> ls(sample_buildout)
    -  b1.cfg
    -  b2.cfg
    -  base.cfg
    d  bin
    -  buildout.cfg
    d  demo
    d  develop-eggs
    d  eggs
    -  inst.cfg
    d  parts
    d  recipes

The installation database can be disabled by supplying an empty
buildout installed option:

    >>> os.remove('inst.cfg')
    >>> print_(system(buildout+' buildout:installed='), end='')
    Develop: '/sample-buildout/recipes'
    Installing debug.
    recipe recipes:debug

    >>> ls(sample_buildout)
    -  b1.cfg
    -  b2.cfg
    -  base.cfg
    d  bin
    -  buildout.cfg
    d  demo
    d  develop-eggs
    d  eggs
    d  parts
    d  recipes


Note that there will be no installation database if there are no parts:

    >>> write('buildout.cfg',
    ... """
    ... [buildout]
    ... parts =
    ... """)

    >>> print_(system(buildout+' buildout:installed=inst.cfg'), end='')

    >>> ls(sample_buildout)
    -  b1.cfg
    -  b2.cfg
    -  base.cfg
    d  bin
    -  buildout.cfg
    d  demo
    d  develop-eggs
    d  eggs
    d  parts
    d  recipes

Extensions
----------

A feature allows code to be loaded and run after
configuration files have been read but before the buildout has begun
any processing.  The intent is to allow special plugins such as
urllib2 request handlers to be loaded.

To load an extension, we use the extensions option and list one or
more distribution requirements, on separate lines.  The distributions
named will be loaded and any ``zc.buildout.extension`` entry points found
will be called with the buildout as an argument.  When buildout
finishes processing, any ``zc.buildout.unloadextension`` entry points
found will be called with the buildout as an argument.

Let's create a sample extension in our sample buildout created in the
previous section:

    >>> mkdir(sample_bootstrapped, 'demo')

    >>> write(sample_bootstrapped, 'demo', 'demo.py',
    ... """
    ... import sys
    ... def ext(buildout):
    ...     sys.stdout.write('%s %s\\n' % ('ext', sorted(buildout)))
    ... def unload(buildout):
    ...     sys.stdout.write('%s %s\\n' % ('unload', sorted(buildout)))
    ... """)

    >>> write(sample_bootstrapped, 'demo', 'setup.py',
    ... """
    ... from setuptools import setup
    ...
    ... setup(
    ...     name = "demo",
    ...     entry_points = {
    ...        'zc.buildout.extension': ['ext = demo:ext'],
    ...        'zc.buildout.unloadextension': ['ext = demo:unload'],
    ...        },
    ...     )
    ... """)

Our extension just prints out the word 'demo', and lists the sections
found in the buildout passed to it.

We'll update our buildout.cfg to list the demo directory as a develop
egg to be built:

    >>> write(sample_bootstrapped, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = demo
    ... parts =
    ... """)

    >>> os.chdir(sample_bootstrapped)
    >>> print_(system(os.path.join(sample_bootstrapped, 'bin', 'buildout')),
    ...        end='')
    Develop: '/sample-bootstrapped/demo'

Now we can add the extensions option.  We were a bit tricky and ran
the buildout once with the demo develop egg defined but without the
extension option.  This is because extensions are loaded before the
buildout creates develop eggs. We needed to use a separate buildout
run to create the develop egg.  Normally, when eggs are loaded from
the network, we wouldn't need to do anything special.

    >>> write(sample_bootstrapped, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = demo
    ... extensions = demo
    ... parts =
    ... """)

We see that our extension is loaded and executed:

    >>> print_(system(os.path.join(sample_bootstrapped, 'bin', 'buildout')),
    ...        end='')
    ext ['buildout', 'versions']
    Develop: '/sample-bootstrapped/demo'
    unload ['buildout', 'versions']

Repeatable buildouts: controlling eggs used
===========================================

One of the goals of zc.buildout is to provide enough control to make
buildouts repeatable.  It should be possible to check the buildout
configuration files for a project into a version control system and
later use the checked in files to get the same buildout, subject to
changes in the environment outside the buildout.

An advantage of using Python eggs is that dependencies of eggs used are
automatically determined and used.  The automatic inclusion of
dependent distributions is at odds with the goal of repeatable
buildouts.

To support repeatable buildouts, a versions section can be created
with options for each distribution name who's version is to be fixed.
The section can then be specified via the buildout versions option.

To see how this works, we'll create two versions of a recipe egg:

    >>> mkdir('recipe')
    >>> write('recipe', 'recipe.py',
    ... '''
    ... import sys
    ... print_ = lambda *a: sys.stdout.write(' '.join(map(str, a))+'\\n')
    ... class Recipe:
    ...     def __init__(*a): pass
    ...     def install(self):
    ...         print_('recipe v1')
    ...         return ()
    ...     update = install
    ... ''')

    >>> write('recipe', 'setup.py',
    ... '''
    ... from setuptools import setup
    ... setup(name='spam', version='1', py_modules=['recipe'],
    ...       entry_points={'zc.buildout': ['default = recipe:Recipe']},
    ...       )
    ... ''')

    >>> write('recipe', 'README', '')

    >>> print_(system(buildout+' setup recipe bdist_egg')) # doctest: +ELLIPSIS
    Running setup script 'recipe/setup.py'.
    ...

    >>> rmdir('recipe', 'build')

    >>> write('recipe', 'recipe.py',
    ... '''
    ... import sys
    ... print_ = lambda *a: sys.stdout.write(' '.join(map(str, a))+'\\n')
    ... class Recipe:
    ...     def __init__(*a): pass
    ...     def install(self):
    ...         print_('recipe v2')
    ...         return ()
    ...     update = install
    ... ''')

    >>> write('recipe', 'setup.py',
    ... '''
    ... from setuptools import setup
    ... setup(name='spam', version='2', py_modules=['recipe'],
    ...       entry_points={'zc.buildout': ['default = recipe:Recipe']},
    ...       )
    ... ''')


    >>> print_(system(buildout+' setup recipe bdist_egg')) # doctest: +ELLIPSIS
    Running setup script 'recipe/setup.py'.
    ...

and we'll configure a buildout to use it:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))

If we run the buildout, it will use version 2:

    >>> print_(system(buildout), end='')
    Getting distribution for 'spam'.
    Got spam 2.
    Installing foo.
    recipe v2

We can specify a versions section that lists our recipe and name it in
the buildout section:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ...
    ... [versions]
    ... spam = 1
    ... eggs = 2.2
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))

Here we created a versions section listing the version 1 for the spam
distribution.  We told the buildout to use it by specifying release-1
as in the versions option.

Now, if we run the buildout, we'll use version 1 of the spam recipe:

    >>> print_(system(buildout), end='')
    Getting distribution for 'spam==1'.
    Got spam 1.
    Uninstalling foo.
    Installing foo.
    recipe v1

Running the buildout in verbose mode will help us get information
about versions used. If we run the buildout in verbose mode without
specifying a versions section:

    >>> print_(system(buildout+' buildout:versions= -v'), end='')
    Installing 'zc.buildout', 'setuptools'.
    We have a develop egg: zc.buildout 1.0.0.
    We have the best distribution that satisfies 'setuptools'.
    Picked: setuptools = 0.6
    Installing 'spam'.
    We have the best distribution that satisfies 'spam'.
    Picked: spam = 2.
    Uninstalling foo.
    Installing foo.
    recipe v2

We'll get output that includes lines that tell us what versions
buildout chose a for us, like::

    zc.buildout.easy_install.picked: spam = 2

This allows us to discover versions that are picked dynamically, so
that we can fix them in a versions section.

If we run the buildout with the versions section:

    >>> print_(system(buildout+' -v'), end='')
    Installing 'zc.buildout', 'setuptools'.
    We have a develop egg: zc.buildout 1.0.0.
    We have the best distribution that satisfies 'setuptools'.
    Picked: setuptools = 0.6
    Installing 'spam'.
    We have the distribution that satisfies 'spam==1'.
    Uninstalling foo.
    Installing foo.
    recipe v1

We won't get output for the spam distribution, which we didn't pick,
but we will get output for setuptools, which we didn't specify
versions for.

.. Edge case: version applied to range requirement:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ...
    ... [versions]
    ... spam = 1
    ... eggs = 2.2
    ...
    ... [foo]
    ... recipe = spam >0
    ... ''' % join('recipe', 'dist'))

    >>> print_(system(buildout+' -v'), end='')
    Installing 'zc.buildout', 'setuptools'.
    We have a develop egg: zc.buildout 1.0.0.
    We have the best distribution that satisfies 'setuptools'.
    Picked: setuptools = 0.6
    Installing 'spam >0'.
    We have the distribution that satisfies 'spam==1'.
    Uninstalling foo.
    Installing foo.
    recipe v1


You can request buildout to generate an error if it picks any
versions:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ... allow-picked-versions = false
    ...
    ... [versions]
    ... spam = 1
    ... eggs = 2.2
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    While:
      Installing.
      Checking for upgrades.
      Getting distribution for 'setuptools'.
    Error: Picked: setuptools = 0.6.30

We can name a version something else, if we wish, using the versions option:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ... versions = release1
    ...
    ... [release1]
    ... spam = 1
    ... eggs = 2.2
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Uninstalling foo.
    Installing foo.
    recipe v1

We can also disable checking versions:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ... versions =
    ...
    ... [versions]
    ... spam = 1
    ... eggs = 2.2
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Uninstalling foo.
    Installing foo.
    recipe v2


Easier reporting and managing of versions (new in buildout 2.0)
---------------------------------------------------------------

Since buildout 2.0, the functionality of the `buildout-versions
<http://packages.python.org/buildout-versions/>`_ extension is part of
buildout itself. This makes reporting and managing versions easier.

Buildout picks a version for setuptools and for the tests, we need to grab the
version number:

    >>> import pkg_resources
    >>> req = pkg_resources.Requirement.parse('setuptools')
    >>> setuptools_version = pkg_resources.working_set.find(req).version

If you set the ``show-picked-versions`` option, buildout will print
versions it picked at the end of its run:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ... show-picked-versions = true
    ...
    ... [versions]
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Updating foo.
    recipe v2
    Versions had to be automatically picked.
    The following part definition lists the versions picked:
    [versions]
    setuptools = 0.6.99
    spam = 2

When everything is pinned, no output is generated:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ... show-picked-versions = true
    ...
    ... [versions]
    ... setuptools = %s
    ... spam = 2
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % (join('recipe', 'dist'), setuptools_version))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Updating foo.
    recipe v2

The Python package index is case-insensitive. Both
http://pypi.python.org/simple/Django/ and
http://pypi.python.org/simple/dJaNgO/ work. And distributions aren't always
naming themselves consistently case-wise. So all version names are normalized
and case differences won't impact the pinning:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... find-links = %s
    ... show-picked-versions = true
    ...
    ... [versions]
    ... setuptools = %s
    ... Spam = 2
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % (join('recipe', 'dist'), setuptools_version))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Updating foo.
    recipe v2

Sometimes it is handy to have a separate file with versions. This is a regular
buildout file with a single ``[versions]`` section. You include it by
extending from that versions file:

    >>> write('my_versions.cfg',
    ... '''
    ... [versions]
    ... setuptools = %s
    ... spam = 2
    ... ''' % setuptools_version)
    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... extends = my_versions.cfg
    ... find-links = %s
    ... show-picked-versions = true
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Updating foo.
    recipe v2

If not everything is pinned and buildout has to pick versions, you can tell
buildout to append the versions to your versions file. It simply appends them
at the end.

    >>> write('my_versions.cfg',
    ... '''
    ... [versions]
    ... setuptools = %s
    ... ''' % setuptools_version)
    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... extends = my_versions.cfg
    ... update-versions-file = my_versions.cfg
    ... find-links = %s
    ... show-picked-versions = true
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Updating foo.
    recipe v2
    Versions had to be automatically picked.
    The following part definition lists the versions picked:
    [versions]
    spam = 2
    Picked versions have been written to my_versions.cfg

The versions file now contains the extra pin:

    >>> print_(open('my_versions.cfg').read()) # doctest: +ELLIPSIS
    <BLANKLINE>
    ...
    <BLANKLINE>
    # Added by buildout at YYYY-MM-DD hh:mm:ss.dddddd
    spam = 2
    <BLANKLINE>

And re-running buildout doesn't report any picked versions anymore:

    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Updating foo.
    recipe v2

If you've enabled ``update-versions-file`` but not ``show-picked-versions``,
buildout will append the versions to your versions file anyway (without
printing them to the console):

    >>> write('my_versions.cfg',
    ... '''
    ... [versions]
    ... setuptools = %s
    ... ''' % setuptools_version)
    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = foo
    ... extends = my_versions.cfg
    ... update-versions-file = my_versions.cfg
    ... find-links = %s
    ... show-picked-versions = false
    ...
    ... [foo]
    ... recipe = spam
    ... ''' % join('recipe', 'dist'))
    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    Updating foo.
    recipe v2
    Picked versions have been written to my_versions.cfg

The versions file contains the extra pin:

    >>> print_(open('my_versions.cfg').read()) # doctest: +ELLIPSIS
    <BLANKLINE>
    ...
    <BLANKLINE>
    # Added by buildout at YYYY-MM-DD hh:mm:ss.dddddd
    spam = 2
    <BLANKLINE>

Because buildout now includes buildout-versions' (and part of the older
buildout.dumppickedversions') functionality, it warns if these extensions are
configured.

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... parts = foo
    ... extensions = buildout-versions
    ...
    ... [foo]
    ... recipe = spam
    ... """)
    >>> print_(system(buildout), end='') # doctest: +NORMALIZE_WHITESPACE
    While:
      Installing.
      Loading extensions.
      Error: Buildout now includes 'buildout-versions'
      (and part of the older 'buildout.dumppickedversions').
      Remove the extension from your configuration and look at the
      'show-picked-versions' option in buildout's documentation.

Using the download utility
==========================

The ``zc.buildout.download`` module provides a download utility that handles
the details of downloading files needed for a buildout run from the internet.
It downloads files to the local file system, using the download cache if
desired and optionally checking the downloaded files' MD5 checksum.

We setup an HTTP server that provides a file we want to download:

>>> server_data = tmpdir('sample_files')
>>> write(server_data, 'foo.txt', 'This is a foo text.')
>>> server_url = start_server(server_data)

We also use a fresh directory for temporary files in order to make sure that
all temporary files have been cleaned up in the end:

>>> import tempfile
>>> old_tempdir = tempfile.tempdir
>>> tempfile.tempdir = tmpdir('tmp')


Downloading without using the cache
-----------------------------------

If no download cache should be used, the download utility is instantiated
without any arguments:

>>> from zc.buildout.download import Download
>>> download = Download()
>>> print_(download.cache_dir)
None

Downloading a file is achieved by calling the utility with the URL as an
argument. A tuple is returned that consists of the path to the downloaded copy
of the file and a boolean value indicating whether this is a temporary file
meant to be cleaned up during the same buildout run:

>>> path, is_temp = download(server_url+'foo.txt')
>>> print_(path)
/.../buildout-...
>>> cat(path)
This is a foo text.

As we aren't using the download cache and haven't specified a target path
either, the download has ended up in a temporary file:

>>> is_temp
True

>>> import tempfile
>>> path.startswith(tempfile.gettempdir())
True

We are responsible for cleaning up temporary files behind us:

>>> remove(path)

When trying to access a file that doesn't exist, we'll get an exception:

>>> try: download(server_url+'not-there') # doctest: +ELLIPSIS
... except: print_('download error')
... else: print_('woops')
download error

Downloading a local file doesn't produce a temporary file but simply returns
the local file itself:

>>> download(join(server_data, 'foo.txt'))
('/sample_files/foo.txt', False)

We can also have the downloaded file's MD5 sum checked:

>>> try: from hashlib import md5
... except ImportError: from md5 import new as md5

>>> path, is_temp = download(server_url+'foo.txt',
...                          md5('This is a foo text.'.encode()).hexdigest())
>>> is_temp
True
>>> remove(path)

>>> download(server_url+'foo.txt',
...          md5('The wrong text.'.encode()).hexdigest())
Traceback (most recent call last):
ChecksumError: MD5 checksum mismatch downloading 'http://localhost/foo.txt'

The error message in the event of an MD5 checksum mismatch for a local file
reads somewhat differently:

>>> download(join(server_data, 'foo.txt'),
...               md5('This is a foo text.'.encode()).hexdigest())
('/sample_files/foo.txt', False)

>>> download(join(server_data, 'foo.txt'),
...          md5('The wrong text.'.encode()).hexdigest())
Traceback (most recent call last):
ChecksumError: MD5 checksum mismatch for local resource at '/sample_files/foo.txt'.

Finally, we can download the file to a specified place in the file system:

>>> target_dir = tmpdir('download-target')
>>> path, is_temp = download(server_url+'foo.txt',
...                          path=join(target_dir, 'downloaded.txt'))
>>> print_(path)
/download-target/downloaded.txt
>>> cat(path)
This is a foo text.
>>> is_temp
False

Trying to download a file in offline mode will result in an error:

>>> download = Download(cache=None, offline=True)
>>> download(server_url+'foo.txt')
Traceback (most recent call last):
UserError: Couldn't download 'http://localhost/foo.txt' in offline mode.

As an exception to this rule, file system paths and URLs in the ``file``
scheme will still work:

>>> cat(download(join(server_data, 'foo.txt'))[0])
This is a foo text.
>>> cat(download('file:' + join(server_data, 'foo.txt'))[0])
This is a foo text.

>>> remove(path)


Downloading using the download cache
------------------------------------

In order to make use of the download cache, we need to configure the download
utility differently. To do this, we pass a directory path as the ``cache``
attribute upon instantiation:

>>> cache = tmpdir('download-cache')
>>> download = Download(cache=cache)
>>> print_(download.cache_dir)
/download-cache/

Simple usage
~~~~~~~~~~~~

When using the cache, a file will be stored in the cache directory when it is
first downloaded. The file system path returned by the download utility points
to the cached copy:

>>> ls(cache)
>>> path, is_temp = download(server_url+'foo.txt')
>>> print_(path)
/download-cache/foo.txt
>>> cat(path)
This is a foo text.
>>> is_temp
False

Whenever the file is downloaded again, the cached copy is used. Let's change
the file on the server to see this:

>>> write(server_data, 'foo.txt', 'The wrong text.')
>>> path, is_temp = download(server_url+'foo.txt')
>>> print_(path)
/download-cache/foo.txt
>>> cat(path)
This is a foo text.

If we specify an MD5 checksum for a file that is already in the cache, the
cached copy's checksum will be verified:

>>> download(server_url+'foo.txt', md5('The wrong text.'.encode()).hexdigest())
Traceback (most recent call last):
ChecksumError: MD5 checksum mismatch for cached download
               from 'http://localhost/foo.txt' at '/download-cache/foo.txt'

Trying to access another file at a different URL which has the same base name
will result in the cached copy being used:

>>> mkdir(server_data, 'other')
>>> write(server_data, 'other', 'foo.txt', 'The wrong text.')
>>> path, is_temp = download(server_url+'other/foo.txt')
>>> print_(path)
/download-cache/foo.txt
>>> cat(path)
This is a foo text.

Given a target path for the download, the utility will provide a copy of the
file at that location both when first downloading the file and when using a
cached copy:

>>> remove(cache, 'foo.txt')
>>> ls(cache)
>>> write(server_data, 'foo.txt', 'This is a foo text.')

>>> path, is_temp = download(server_url+'foo.txt',
...                          path=join(target_dir, 'downloaded.txt'))
>>> print_(path)
/download-target/downloaded.txt
>>> cat(path)
This is a foo text.
>>> is_temp
False
>>> ls(cache)
- foo.txt

>>> remove(path)
>>> write(server_data, 'foo.txt', 'The wrong text.')

>>> path, is_temp = download(server_url+'foo.txt',
...                          path=join(target_dir, 'downloaded.txt'))
>>> print_(path)
/download-target/downloaded.txt
>>> cat(path)
This is a foo text.
>>> is_temp
False

In offline mode, downloads from any URL will be successful if the file is
found in the cache:

>>> download = Download(cache=cache, offline=True)
>>> cat(download(server_url+'foo.txt')[0])
This is a foo text.

Local resources will be cached just like any others since download caches are
sometimes used to create source distributions:

>>> remove(cache, 'foo.txt')
>>> ls(cache)

>>> write(server_data, 'foo.txt', 'This is a foo text.')
>>> download = Download(cache=cache)

>>> cat(download('file:' + join(server_data, 'foo.txt'), path=path)[0])
This is a foo text.
>>> ls(cache)
- foo.txt

>>> remove(cache, 'foo.txt')

>>> cat(download(join(server_data, 'foo.txt'), path=path)[0])
This is a foo text.
>>> ls(cache)
- foo.txt

>>> remove(cache, 'foo.txt')

However, resources with checksum mismatches will not be copied to the cache:

>>> download(server_url+'foo.txt', md5('The wrong text.'.encode()).hexdigest())
Traceback (most recent call last):
ChecksumError: MD5 checksum mismatch downloading 'http://localhost/foo.txt'
>>> ls(cache)

>>> remove(path)

If the file is completely missing it should notify the user of the error:

>>> download(server_url+'bar.txt') # doctest: +NORMALIZE_WHITESPACE +ELLIPSIS
Traceback (most recent call last):
...
UserError: Error downloading extends for URL http://localhost/bar.txt:
...404...
>>> ls(cache)

Finally, let's see what happens if the download cache to be used doesn't exist
as a directory in the file system yet:

>>> Download(cache=join(cache, 'non-existent'))(server_url+'foo.txt')
Traceback (most recent call last):
UserError: The directory:
'/download-cache/non-existent'
to be used as a download cache doesn't exist.

Using namespace sub-directories of the download cache
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It is common to store cached copies of downloaded files within sub-directories
of the download cache to keep some degree of order. For example, zc.buildout
stores downloaded distributions in a sub-directory named "dist". Those
sub-directories are also known as namespaces. So far, we haven't specified any
namespaces to use, so the download utility stored files directly inside the
download cache. Let's use a namespace "test" instead:

>>> download = Download(cache=cache, namespace='test')
>>> print_(download.cache_dir)
/download-cache/test

The namespace sub-directory hasn't been created yet:

>>> ls(cache)

Downloading a file now creates the namespace sub-directory and places a copy
of the file inside it:

>>> path, is_temp = download(server_url+'foo.txt')
>>> print_(path)
/download-cache/test/foo.txt
>>> ls(cache)
d test
>>> ls(cache, 'test')
- foo.txt
>>> cat(path)
This is a foo text.
>>> is_temp
False

The next time we want to download that file, the copy from inside the cache
namespace is used. To see this clearly, we put a file with the same name but
different content both on the server and in the cache's root directory:

>>> write(server_data, 'foo.txt', 'The wrong text.')
>>> write(cache, 'foo.txt', 'The wrong text.')

>>> path, is_temp = download(server_url+'foo.txt')
>>> print_(path)
/download-cache/test/foo.txt
>>> cat(path)
This is a foo text.

>>> rmdir(cache, 'test')
>>> remove(cache, 'foo.txt')
>>> write(server_data, 'foo.txt', 'This is a foo text.')

Using a hash of the URL as the filename in the cache
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

So far, the base name of the downloaded file read from the URL has been used
for the name of the cached copy of the file. This may not be desirable in some
cases, for example when downloading files from different locations that have
the same base name due to some naming convention, or if the file content
depends on URL parameters. In such cases, an MD5 hash of the complete URL may
be used as the filename in the cache:

>>> download = Download(cache=cache, hash_name=True)
>>> path, is_temp = download(server_url+'foo.txt')
>>> print_(path)
/download-cache/09f5793fcdc1716727f72d49519c688d
>>> cat(path)
This is a foo text.
>>> ls(cache)
- 09f5793fcdc1716727f72d49519c688d

The path was printed just to illustrate matters; we cannot know the real
checksum since we don't know which port the server happens to listen at when
the test is run, so we don't actually know the full URL of the file. Let's
check that the checksum actually belongs to the particular URL used:

>>> (path.lower() ==
...  join(cache, md5((server_url+'foo.txt').encode()).hexdigest()).lower())
True

The cached copy is used when downloading the file again:

>>> write(server_data, 'foo.txt', 'The wrong text.')
>>> (path, is_temp) == download(server_url+'foo.txt')
True
>>> cat(path)
This is a foo text.
>>> ls(cache)
- 09f5793fcdc1716727f72d49519c688d

If we change the URL, even in such a way that it keeps the base name of the
file the same, the file will be downloaded again this time and put in the
cache under a different name:

>>> path2, is_temp = download(server_url+'other/foo.txt')
>>> print_(path2)
/download-cache/537b6d73267f8f4447586989af8c470e
>>> path == path2
False
>>> (path2.lower() ==
...  join(cache, md5((server_url+'other/foo.txt').encode()).hexdigest()
...       ).lower())
True
>>> cat(path)
This is a foo text.
>>> cat(path2)
The wrong text.
>>> ls(cache)
- 09f5793fcdc1716727f72d49519c688d
- 537b6d73267f8f4447586989af8c470e

>>> remove(path)
>>> remove(path2)
>>> write(server_data, 'foo.txt', 'This is a foo text.')


Using the cache purely as a fall-back
-------------------------------------

Sometimes it is desirable to try downloading a file from the net if at all
possible, and use the cache purely as a fall-back option when a server is
down or if we are in offline mode. This mode is only in effect if a download
cache is configured in the first place:

>>> download = Download(cache=cache, fallback=True)
>>> print_(download.cache_dir)
/download-cache/

A downloaded file will be cached:

>>> ls(cache)
>>> path, is_temp = download(server_url+'foo.txt')
>>> ls(cache)
- foo.txt
>>> cat(cache, 'foo.txt')
This is a foo text.
>>> is_temp
False

If the file cannot be served, the cached copy will be used:

>>> remove(server_data, 'foo.txt')
>>> try: Download()(server_url+'foo.txt') # doctest: +ELLIPSIS
... except: print_('download error')
... else: print_('woops')
download error
>>> path, is_temp = download(server_url+'foo.txt')
>>> cat(path)
This is a foo text.
>>> is_temp
False

Similarly, if the file is served but we're in offline mode, we'll fall back to
using the cache:

>>> write(server_data, 'foo.txt', 'The wrong text.')
>>> get(server_url+'foo.txt')
'The wrong text.'

>>> offline_download = Download(cache=cache, offline=True, fallback=True)
>>> path, is_temp = offline_download(server_url+'foo.txt')
>>> print_(path)
/download-cache/foo.txt
>>> cat(path)
This is a foo text.
>>> is_temp
False

However, when downloading the file normally with the cache being used in
fall-back mode, the file will be downloaded from the net and the cached copy
will be replaced with the new content:

>>> cat(download(server_url+'foo.txt')[0])
The wrong text.
>>> cat(cache, 'foo.txt')
The wrong text.

When trying to download a resource whose checksum does not match, the cached
copy will neither be used nor overwritten:

>>> write(server_data, 'foo.txt', 'This is a foo text.')
>>> download(server_url+'foo.txt', md5('The wrong text.'.encode()).hexdigest())
Traceback (most recent call last):
ChecksumError: MD5 checksum mismatch downloading 'http://localhost/foo.txt'
>>> cat(cache, 'foo.txt')
The wrong text.


Configuring the download utility from buildout options
------------------------------------------------------

The configuration options explained so far derive from the build logic
implemented by the calling code. Other options configure the download utility
for use in a particular project or buildout run; they are read from the
``buildout`` configuration section. The latter can be passed directly as the
first argument to the download utility's constructor.

The location of the download cache is specified by the ``download-cache``
option:

>>> download = Download({'download-cache': cache}, namespace='cmmi')
>>> print_(download.cache_dir)
/download-cache/cmmi

If the ``download-cache`` option specifies a relative path, it is understood
relative to the current working directory, or to the buildout directory if
that is given:

>>> download = Download({'download-cache': 'relative-cache'})
>>> print_(download.cache_dir)
/sample-buildout/relative-cache/

>>> download = Download({'directory': join(sample_buildout, 'root'),
...                      'download-cache': 'relative-cache'})
>>> print_(download.cache_dir)
/sample-buildout/root/relative-cache/

Keyword parameters take precedence over the corresponding options:

>>> download = Download({'download-cache': cache}, cache=None)
>>> print_(download.cache_dir)
None

Whether to assume offline mode can be inferred from either the ``offline`` or
the ``install-from-cache`` option. As usual with zc.buildout, these options
must assume one of the values 'true' and 'false':

>>> download = Download({'offline': 'true'})
>>> download.offline
True

>>> download = Download({'offline': 'false'})
>>> download.offline
False

>>> download = Download({'install-from-cache': 'true'})
>>> download.offline
True

>>> download = Download({'install-from-cache': 'false'})
>>> download.offline
False

These two options are combined using logical 'or':

>>> download = Download({'offline': 'true', 'install-from-cache': 'false'})
>>> download.offline
True

>>> download = Download({'offline': 'false', 'install-from-cache': 'true'})
>>> download.offline
True

The ``offline`` keyword parameter takes precedence over both the ``offline``
and ``install-from-cache`` options:

>>> download = Download({'offline': 'true'}, offline=False)
>>> download.offline
False

>>> download = Download({'install-from-cache': 'false'}, offline=True)
>>> download.offline
True


Regressions
-----------

MD5 checksum calculation needs to be reliable on all supported systems, which
requires text files to be treated as binary to avoid implicit line-ending
conversions:

>>> text = 'First line of text.\r\nSecond line.\r\n'
>>> f = open(join(server_data, 'foo.txt'), 'wb')
>>> _ = f.write(text.encode())
>>> f.close()
>>> path, is_temp = Download()(server_url+'foo.txt',
...                            md5(text.encode()).hexdigest())
>>> remove(path)

When "downloading" a directory given by file-system path or ``file:`` URL and
using a download cache at the same time, the cached directory wasn't handled
correctly. Consequently, the cache was defeated and an attempt to cache the
directory a second time broke. This is how it should work:

>>> download = Download(cache=cache)
>>> dirpath = join(server_data, 'some_directory')
>>> mkdir(dirpath)
>>> dest, _ = download(dirpath)

If we now modify the source tree, the second download will produce the
original one from the cache:

>>> mkdir(join(dirpath, 'foo'))
>>> ls(dirpath)
d foo
>>> dest, _ = download(dirpath)
>>> ls(dest)


Clean up
--------

We should have cleaned up all temporary files created by downloading things:

>>> ls(tempfile.tempdir)

Reset the global temporary directory:

>>> tempfile.tempdir = old_tempdir

Using a download cache
======================

Normally, when distributions are installed, if any processing is
needed, they are downloaded from the internet to a temporary directory
and then installed from there.  A download cache can be used to avoid
the download step.  This can be useful to reduce network access and to
create source distributions of an entire buildout.

The buildout download-cache option can be used to specify a directory
to be used as a download cache.

In this example, we'll create a directory to hold the cache:

    >>> cache = tmpdir('cache')

And set up a buildout that downloads some eggs:

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = eggs
    ... download-cache = %(cache)s
    ... find-links = %(link_server)s
    ...
    ... [eggs]
    ... recipe = zc.recipe.egg
    ... eggs = demo ==0.2
    ... ''' % globals())

We specified a link server that has some distributions available for
download:

    >>> print_(get(link_server), end='')
    <html><body>
    <a href="bigdemo-0.1-py2.4.egg">bigdemo-0.1-py2.4.egg</a><br>
    <a href="demo-0.1-py2.4.egg">demo-0.1-py2.4.egg</a><br>
    <a href="demo-0.2-py2.4.egg">demo-0.2-py2.4.egg</a><br>
    <a href="demo-0.3-py2.4.egg">demo-0.3-py2.4.egg</a><br>
    <a href="demo-0.4rc1-py2.4.egg">demo-0.4rc1-py2.4.egg</a><br>
    <a href="demoneeded-1.0.zip">demoneeded-1.0.zip</a><br>
    <a href="demoneeded-1.1.zip">demoneeded-1.1.zip</a><br>
    <a href="demoneeded-1.2rc1.zip">demoneeded-1.2rc1.zip</a><br>
    <a href="du_zipped-1.0-pyN.N.egg">du_zipped-1.0-pyN.N.egg</a><br>
    <a href="extdemo-1.4.zip">extdemo-1.4.zip</a><br>
    <a href="index/">index/</a><br>
    <a href="other-1.0-py2.4.egg">other-1.0-py2.4.egg</a><br>
    </body></html>


We'll enable logging on the link server so we can see what's going on:

    >>> _ = get(link_server+'enable_server_logging')
    GET 200 /enable_server_logging

We also specified a download cache.

If we run the buildout, we'll see the eggs installed from the link
server as usual:

    >>> print_(system(buildout), end='')
    GET 200 /
    GET 200 /demo-0.2-py2.4.egg
    GET 200 /demoneeded-1.1.zip
    Installing eggs.
    Getting distribution for 'demo==0.2'.
    Got demo 0.2.
    Getting distribution for 'demoneeded'.
    Got demoneeded 1.1.
    Generated script '/sample-buildout/bin/demo'.

We'll also get the download cache populated.  The buildout doesn't put
files in the cache directly.  It creates an intermediate directory,
dist:


    >>> ls(cache)
    d  dist

    >>> ls(cache, 'dist')
    -  demo-0.2-py2.4.egg
    -  demoneeded-1.1.zip

If we remove the installed eggs from eggs directory and re-run the buildout:

    >>> import os
    >>> for  f in os.listdir('eggs'):
    ...     if f.startswith('demo'):
    ...         remove('eggs', f)

    >>> print_(system(buildout), end='')
    GET 200 /
    Updating eggs.
    Getting distribution for 'demo==0.2'.
    Got demo 0.2.
    Getting distribution for 'demoneeded'.
    Got demoneeded 1.1.

We see that the distributions aren't downloaded, because they're
downloaded from the cache.

Installing solely from a download cache
---------------------------------------

A download cache can be used as the basis of application source
releases.  In an application source release, we want to distribute an
application that can be built without making any network accesses.  In
this case, we distribute a buildout with download cache and tell the
buildout to install from the download cache only, without making
network accesses.  The buildout install-from-cache option can be used
to signal that packages should be installed only from the download
cache.

Let's remove our installed eggs and run the buildout with the
install-from-cache option set to true:

    >>> for  f in os.listdir('eggs'):
    ...     if f.startswith('demo'):
    ...         remove('eggs', f)

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts = eggs
    ... download-cache = %(cache)s
    ... install-from-cache = true
    ... find-links = %(link_server)s
    ...
    ... [eggs]
    ... recipe = zc.recipe.egg
    ... eggs = demo
    ... ''' % globals())

    >>> print_(system(buildout), end='')
    Uninstalling eggs.
    Installing eggs.
    Getting distribution for 'demo'.
    Got demo 0.2.
    Getting distribution for 'demoneeded'.
    Got demoneeded 1.1.
    Generated script '/sample-buildout/bin/demo'.

Auto-creation of download cache directory
-----------------------------------------

With zc.buildout version 2.2.2 or higher the cache directory is automatically
created::

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts =
    ... download-cache = %(cache)s/newdir
    ... ''' % globals())

    >>> print_(system(buildout), end='')
    Creating directory '/cache/newdir'.
    Uninstalling eggs.

    >>> ls(cache)
    d  dist
    d  newdir

Using relative paths
--------------------

You can use a relative path for ``download-cache`` (the same logic is applied to
``eggs-directory`` and to ``extends-cache`` too) and in such case it is considered
relative to the location of the configuration file that sets its value.

As an example, we create a ``base.cfg`` configuration in a different directory::

    >>> basedir = tmpdir('basecfg')
    >>> write(basedir, 'base.cfg',
    ... '''
    ... [buildout]
    ... download-cache = cache
    ... ''')

and a ``buildout.cfg`` that extends from there::

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... extends = %(basedir)s/base.cfg
    ... parts =
    ... ''' % globals())

    >>> dummy = system(buildout)
    >>> ls(basedir)
    -  base.cfg
    d  cache

Of course this cannot be used when the base configuration is not on the local
filesystem because it wouldn't make any sense having a remote cache::

    >>> server_data = tmpdir('server_data')
    >>> server_url = start_server(server_data)
    >>> cd(sample_buildout)

    >>> write(server_data, 'base.cfg', """\
    ... [buildout]
    ... download-cache = cache
    ... """)

    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... extends = %(server_url)s/base.cfg
    ... parts =
    ... ''' % globals())

    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
    While:
      Initializing.
    Error: Setting "download-cache" to a non absolute location ("cache") within a
    remote configuration file...

Though, you can create the ``download-cache`` within a nested directory, so that you can
group all your generated directories (like ``eggs-directory`` or ``extends-cache`` too)
within a single directory:

    >>> test_nested = tmpdir('test_nested')
    >>> cd(test_nested)
    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... download-cache = ${buildout:directory}/var/cache
    ... eggs-directory = ${buildout:directory}/var/eggs
    ... parts-directory = ${buildout:directory}/var/parts
    ... develop-eggs-directory = ${buildout:directory}/var/develop-eggs
    ... ''')

    >>> dummy = system(buildout)
    >>> ls(test_nested)
    d  bin
    -  buildout.cfg
    d  var
    >>> ls(os.path.join(test_nested, 'var'))
    d  cache
    d  develop-eggs
    d  eggs
    d  parts


Caching extended configuration
==============================

As mentioned in the general buildout documentation, configuration files can
extend each other, including the ability to download configuration being
extended from a URL. If desired, zc.buildout caches downloaded configuration
in order to be able to use it when run offline.

As we're going to talk about downloading things, let's start an HTTP server.
Also, all of the following will take place inside the sample buildout.

>>> server_data = tmpdir('server_data')
>>> server_url = start_server(server_data)
>>> cd(sample_buildout)

We also use a fresh directory for temporary files in order to make sure that
all temporary files have been cleaned up in the end:

>>> import tempfile
>>> old_tempdir = tempfile.tempdir
>>> tempfile.tempdir = tmpdir('tmp')


Basic use of the extends cache
------------------------------

We put some base configuration on a server and reference it from a sample
buildout:

>>> write(server_data, 'base.cfg', """\
... [buildout]
... parts =
... foo = bar
... """)

>>> write('buildout.cfg', """\
... [buildout]
... extends = %sbase.cfg
... """ % server_url)

When trying to run this buildout offline, we'll find that we cannot read all
of the required configuration:

>>> print_(system(buildout + ' -o'))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base.cfg' in offline mode.

Trying the same online, we can:

>>> print_(system(buildout))
Unused options for buildout: 'foo'.

As long as we haven't said anything about caching downloaded configuration,
nothing gets cached. Offline mode will still cause the buildout to fail:

>>> print_(system(buildout + ' -o'))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base.cfg' in offline mode.

Let's now specify a cache for base configuration files. This cache is
different from the download cache used by recipes for caching distributions
and other files; one might, however, use a namespace subdirectory of the
download cache for it. The configuration cache we specify will be created when
running buildout and the base.cfg file will be put in it (with the file name
being a hash of the complete URL):

>>> mkdir('cache')
>>> write('buildout.cfg', """\
... [buildout]
... extends = %sbase.cfg
... extends-cache = cache
... """ % server_url)

>>> print_(system(buildout))
Unused options for buildout: 'foo'.

>>> cache = join(sample_buildout, 'cache')
>>> ls(cache)
-  5aedc98d7e769290a29d654a591a3a45

>>> import os
>>> cat(cache, os.listdir(cache)[0])
[buildout]
parts =
foo = bar

We can now run buildout offline as it will read base.cfg from the cache:

>>> print_(system(buildout + ' -o'))
Unused options for buildout: 'foo'.

The cache is being used purely as a fall-back in case we are offline or don't
have access to a configuration file to be downloaded. As long as we are
online, buildout attempts to download a fresh copy of each file even if a
cached copy of the file exists. To see this, we put different configuration in
the same place on the server and run buildout in offline mode so it takes
base.cfg from the cache:

>>> write(server_data, 'base.cfg', """\
... [buildout]
... parts =
... bar = baz
... """)

>>> print_(system(buildout + ' -o'))
Unused options for buildout: 'foo'.

In online mode, buildout will download and use the modified version:

>>> print_(system(buildout))
Unused options for buildout: 'bar'.

Trying offline mode again, the new version will be used as it has been put in
the cache now:

>>> print_(system(buildout + ' -o'))
Unused options for buildout: 'bar'.

Clean up:

>>> rmdir(cache)


Specifying extends cache and offline mode
-----------------------------------------

Normally, the values of buildout options such as the location of a download
cache or whether to use offline mode are determined by first reading the
user's default configuration, updating it with the project's configuration and
finally applying command-line options. User and project configuration are
assembled by reading a file such as ``~/.buildout/default.cfg``,
``buildout.cfg`` or a URL given on the command line, recursively (depth-first)
downloading any base configuration specified by the ``buildout:extends``
option read from each of those config files, and finally evaluating each
config file to provide default values for options not yet read.

This works fine for all options that do not influence how configuration is
downloaded in the first place. The ``extends-cache`` and ``offline`` options,
however, are treated differently from the procedure described in order to make
it simple and obvious to see where a particular configuration file came from
under any particular circumstances.

- Offline and extends-cache settings are read from the two root config files
  exclusively. Otherwise one could construct configuration files that, when
  read, imply that they should have been read from a different source than
  they have. Also, specifying the extends cache within a file that might have
  to be taken from the cache before being read wouldn't make a lot of sense.

- Offline and extends-cache settings given by the user's defaults apply to the
  process of assembling the project's configuration. If no extends cache has
  been specified by the user's default configuration, the project's root
  config file must be available, be it from disk or from the net.

- Offline mode turned on by the ``-o`` command line option is honored from
  the beginning even though command line options are applied to the
  configuration last. If offline mode is not requested by the command line, it
  may be switched on by either the user's or the project's config root.

Extends cache
~~~~~~~~~~~~~

Let's see the above rules in action. We create a new home directory for our
user and write user and project configuration that recursively extends online
bases, using different caches:

>>> mkdir('home')
>>> mkdir('home', '.buildout')
>>> mkdir('cache')
>>> mkdir('user-cache')
>>> os.environ['HOME'] = join(sample_buildout, 'home')
>>> write('home', '.buildout', 'default.cfg', """\
... [buildout]
... extends = fancy_default.cfg
... extends-cache = user-cache
... """)
>>> write('home', '.buildout', 'fancy_default.cfg', """\
... [buildout]
... extends = %sbase_default.cfg
... """ % server_url)
>>> write(server_data, 'base_default.cfg', """\
... [buildout]
... foo = bar
... offline = false
... """)

>>> write('buildout.cfg', """\
... [buildout]
... extends = fancy.cfg
... extends-cache = cache
... """)
>>> write('fancy.cfg', """\
... [buildout]
... extends = %sbase.cfg
... """ % server_url)
>>> write(server_data, 'base.cfg', """\
... [buildout]
... parts =
... offline = false
... """)

Buildout will now assemble its configuration from all of these 6 files,
defaults first. The online resources end up in the respective extends caches:

>>> print_(system(buildout))
Unused options for buildout: 'foo'.

>>> ls('user-cache')
-  10e772cf422123ef6c64ae770f555740
>>> cat('user-cache', os.listdir('user-cache')[0])
[buildout]
foo = bar
offline = false

>>> ls('cache')
-  c72213127e6eb2208a3e1fc1dba771a7
>>> cat('cache', os.listdir('cache')[0])
[buildout]
parts =
offline = false

If, on the other hand, the extends caches are specified in files that get
extended themselves, they won't be used for assembling the configuration they
belong to (user's or project's, resp.). The extends cache specified by the
user's defaults does, however, apply to downloading project configuration.
Let's rewrite the config files, clean out the caches and re-run buildout:

>>> write('home', '.buildout', 'default.cfg', """\
... [buildout]
... extends = fancy_default.cfg
... """)
>>> write('home', '.buildout', 'fancy_default.cfg', """\
... [buildout]
... extends = %sbase_default.cfg
... extends-cache = user-cache
... """ % server_url)

>>> write('buildout.cfg', """\
... [buildout]
... extends = fancy.cfg
... """)
>>> write('fancy.cfg', """\
... [buildout]
... extends = %sbase.cfg
... extends-cache = cache
... """ % server_url)

>>> remove('user-cache', os.listdir('user-cache')[0])
>>> remove('cache', os.listdir('cache')[0])

>>> print_(system(buildout))
Unused options for buildout: 'foo'.

>>> ls('user-cache')
-  0548bad6002359532de37385bb532e26
>>> cat('user-cache', os.listdir('user-cache')[0])
[buildout]
parts =
offline = false

>>> ls('cache')

Clean up:

>>> rmdir('user-cache')
>>> rmdir('cache')

Offline mode and installation from cache
----------------------------------------

If we run buildout in offline mode now, it will fail because it cannot get at
the remote configuration file needed by the user's defaults:

>>> print_(system(buildout + ' -o'))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base_default.cfg' in offline mode.

Let's now successively turn on offline mode by different parts of the
configuration and see when buildout applies this setting in each case:

>>> write('home', '.buildout', 'default.cfg', """\
... [buildout]
... extends = fancy_default.cfg
... offline = true
... """)
>>> print_(system(buildout))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base_default.cfg' in offline mode.

>>> write('home', '.buildout', 'default.cfg', """\
... [buildout]
... extends = fancy_default.cfg
... """)
>>> write('home', '.buildout', 'fancy_default.cfg', """\
... [buildout]
... extends = %sbase_default.cfg
... offline = true
... """ % server_url)
>>> print_(system(buildout))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base.cfg' in offline mode.

>>> write('home', '.buildout', 'fancy_default.cfg', """\
... [buildout]
... extends = %sbase_default.cfg
... """ % server_url)
>>> write('buildout.cfg', """\
... [buildout]
... extends = fancy.cfg
... offline = true
... """)
>>> print_(system(buildout))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base.cfg' in offline mode.

>>> write('buildout.cfg', """\
... [buildout]
... extends = fancy.cfg
... """)
>>> write('fancy.cfg', """\
... [buildout]
... extends = %sbase.cfg
... offline = true
... """ % server_url)
>>> print_(system(buildout))
Unused options for buildout: 'foo'.

The ``install-from-cache`` option is treated accordingly:

>>> write('home', '.buildout', 'default.cfg', """\
... [buildout]
... extends = fancy_default.cfg
... install-from-cache = true
... """)
>>> print_(system(buildout))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base_default.cfg' in offline mode.

>>> write('home', '.buildout', 'default.cfg', """\
... [buildout]
... extends = fancy_default.cfg
... """)
>>> write('home', '.buildout', 'fancy_default.cfg', """\
... [buildout]
... extends = %sbase_default.cfg
... install-from-cache = true
... """ % server_url)
>>> print_(system(buildout))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base.cfg' in offline mode.

>>> write('home', '.buildout', 'fancy_default.cfg', """\
... [buildout]
... extends = %sbase_default.cfg
... """ % server_url)
>>> write('buildout.cfg', """\
... [buildout]
... extends = fancy.cfg
... install-from-cache = true
... """)
>>> print_(system(buildout))
While:
  Initializing.
Error: Couldn't download 'http://localhost/base.cfg' in offline mode.

>>> write('buildout.cfg', """\
... [buildout]
... extends = fancy.cfg
... """)
>>> write('fancy.cfg', """\
... [buildout]
... extends = %sbase.cfg
... install-from-cache = true
... """ % server_url)
>>> print_(system(buildout))
While:
  Installing.
  Checking for upgrades.
An internal error occurred ...
ValueError: install_from_cache set to true with no download cache

>>> rmdir('home', '.buildout')

Newest and non-newest behavior for extends cache
-------------------------------------------------

While offline mode forbids network access completely, 'newest' mode determines
whether to look for updated versions of a resource even if some version of it
is already present locally. If we run buildout in newest mode
(``newest = true``), the configuration files are updated with each run:

>>> mkdir("cache")
>>> write(server_data, 'base.cfg', """\
... [buildout]
... parts =
... """)
>>> write('buildout.cfg', """\
... [buildout]
... extends-cache = cache
... extends = %sbase.cfg
... """ % server_url)
>>> print_(system(buildout))
>>> ls('cache')
-  5aedc98d7e769290a29d654a591a3a45
>>> cat('cache', os.listdir(cache)[0])
[buildout]
parts =

A change to ``base.cfg`` is picked up on the next buildout run:

>>> write(server_data, 'base.cfg', """\
... [buildout]
... parts =
... foo = bar
... """)
>>> print_(system(buildout + " -n"))
Unused options for buildout: 'foo'.
>>> cat('cache', os.listdir(cache)[0])
[buildout]
parts =
foo = bar

In contrast, when not using ``newest`` mode (``newest = false``), the files
already present in the extends cache will not be updated:

>>> write(server_data, 'base.cfg', """\
... [buildout]
... parts =
... """)
>>> print_(system(buildout + " -N"))
Unused options for buildout: 'foo'.
>>> cat('cache', os.listdir(cache)[0])
[buildout]
parts =
foo = bar

Even when updating base configuration files with a buildout run, any given
configuration file will be downloaded only once during that particular run. If
some base configuration file is extended more than once, its cached copy is
used:

>>> write(server_data, 'baseA.cfg', """\
... [buildout]
... extends = %sbase.cfg
... foo = bar
... """ % server_url)
>>> write(server_data, 'baseB.cfg', """\
... [buildout]
... extends-cache = cache
... extends = %sbase.cfg
... bar = foo
... """ % server_url)
>>> write('buildout.cfg', """\
... [buildout]
... extends-cache = cache
... newest = true
... extends = %sbaseA.cfg %sbaseB.cfg
... """ % (server_url, server_url))
>>> print_(system(buildout + " -n"))
Unused options for buildout: 'bar' 'foo'.

(XXX We patch download utility's API to produce readable output for the test;
a better solution would re-use the logging already done by the utility.)

>>> import zc.buildout
>>> old_download = zc.buildout.download.Download.download
>>> def wrapper_download(self, url, md5sum=None, path=None):
...   print_("The URL %s was downloaded." % url)
...   return old_download(url, md5sum, path)
>>> zc.buildout.download.Download.download = wrapper_download

>>> zc.buildout.buildout.main([])
The URL http://localhost/baseA.cfg was downloaded.
The URL http://localhost/base.cfg was downloaded.
The URL http://localhost/baseB.cfg was downloaded.
Not upgrading because not running a local buildout command.
Unused options for buildout: 'bar' 'foo'.

>>> zc.buildout.download.Download.download = old_download


The deprecated ``extended-by`` option
-------------------------------------

The ``buildout`` section used to recognize an option named ``extended-by``
that was deprecated at some point and removed in the 1.5 line. Since ignoring
this option silently was considered harmful as a matter of principle, a
UserError is raised if that option is encountered now:

>>> write(server_data, 'base.cfg', """\
... [buildout]
... parts =
... extended-by = foo.cfg
... """)
>>> print_(system(buildout))
While:
  Initializing.
Error: No-longer supported "extended-by" option found in http://localhost/base.cfg.


Reporting cached locations for downloads of faulty config files
---------------------------------------------------------------

A downloaded config file might be invalid. A cancelled buildout run, an
accidentally gzip-encoded download and so on.

>>> write(server_data, 'faulty.cfg', """\
... This is definitively not
... a proper() config file.
... """)

>>> write('buildout.cfg', """\
... [buildout]
... extends = %sfaulty.cfg
... """ % server_url)
>>> print_(system(buildout))
While:
  Initializing.
... File contains no section headers.
file: http://localhost/faulty.cfg (downloaded as ...), line: 1
'This is definitively not\n'


Clean up
--------

We should have cleaned up all temporary files created by downloading things:

>>> ls(tempfile.tempdir)

Reset the global temporary directory:

>>> tempfile.tempdir = old_tempdir

Using zc.buildout to run setup scripts
======================================

zc buildout has a convenience command for running setup scripts.  Why?
There are two reasons.  If a setup script doesn't import setuptools,
you can't use any setuptools-provided commands, like bdist_egg.  When
buildout runs a setup script, it arranges to import setuptools before
running the script so setuptools-provided commands are available.

If you use a squeaky-clean Python to do your development, the setup
script that would import setuptools because setuptools isn't in the
path.  Because buildout requires setuptools and knows where it has
installed a setuptools egg, it adds the setuptools egg to the Python
path before running the script.  To run a setup script, use the
buildout setup command, passing the name of a script or a directory
containing a setup script and arguments to the script.  Let's look at
an example:

    >>> mkdir('test')
    >>> cd('test')
    >>> write('setup.py',
    ... '''
    ... from distutils.core import setup
    ... setup(name='sample')
    ... ''')

We've created a super simple (stupid) setup script.  Note that it
doesn't import setuptools.  Let's try running it to create an egg.
We'll use the buildout script from our sample buildout:

    >>> print_(system(buildout+' setup'), end='')
    ... # doctest: +NORMALIZE_WHITESPACE
    Creating directory '/sample-buildout/test/eggs'.
    Error: The setup command requires the path to a setup script or
    directory containing a setup script, and its arguments.

Oops, we forgot to give the name of the setup script:

    >>> print_(system(buildout+' setup setup.py bdist_egg'))
    ... # doctest: +ELLIPSIS
    Running setup script 'setup.py'.
    ...

    >>> ls('dist')
    -  sample-0.0.0-py2.5.egg

Note that we can specify a directory name.  This is often shorter and
preferred by the lazy :)

    >>> print_(system(buildout+' setup . bdist_egg')) # doctest: +ELLIPSIS
    Running setup script './setup.py'.
    ...

Automatic Buildout Updates
==========================

When a buildout is run, one of the first steps performed is to check for
updates to either zc.buildout or setuptools.  To
demonstrate this, we've created some "new releases" of buildout and
setuptools in a new_releases folder:

    >>> ls(new_releases)
    d  setuptools
    -  setuptools-99.99-py2.4.egg
    d  zc.buildout
    -  zc.buildout-99.99-py2.4.egg

Let's update the sample buildout.cfg to look in this area:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... find-links = %(new_releases)s
    ... index = %(new_releases)s
    ... parts = show-versions
    ... develop = showversions
    ...
    ... [show-versions]
    ... recipe = showversions
    ... """ % dict(new_releases=new_releases))

We'll also include a recipe that echos the versions of setuptools and
zc.buildout used:

    >>> mkdir(sample_buildout, 'showversions')

    >>> write(sample_buildout, 'showversions', 'showversions.py',
    ... """
    ... import pkg_resources
    ... import sys
    ... print_ = lambda *a: sys.stdout.write(' '.join(map(str, a))+'\\n')
    ...
    ... class Recipe:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         pass
    ...
    ...     def install(self):
    ...         for project in 'zc.buildout', 'setuptools':
    ...             req = pkg_resources.Requirement.parse(project)
    ...             print_(project, pkg_resources.working_set.find(req).version)
    ...         return ()
    ...     update = install
    ... """)


    >>> write(sample_buildout, 'showversions', 'setup.py',
    ... """
    ... from setuptools import setup
    ...
    ... setup(
    ...     name = "showversions",
    ...     entry_points = {'zc.buildout': ['default = showversions:Recipe']},
    ...     )
    ... """)


Now if we run the buildout, the buildout will upgrade itself to the
new versions found in new releases:

    >>> print_(system(buildout), end='')
    Getting distribution for 'zc.buildout>=1.99'.
    Got zc.buildout 99.99.
    Getting distribution for 'setuptools'.
    Got setuptools 99.99.
    Upgraded:
      zc.buildout version 99.99,
      setuptools version 99.99;
    restarting.
    Generated script '/sample-buildout/bin/buildout'.
    Develop: '/sample-buildout/showversions'
    Installing show-versions.
    zc.buildout 99.99
    setuptools 99.99

Our buildout script has been updated to use the new eggs:

    >>> cat(sample_buildout, 'bin', 'buildout')
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import sys
    sys.path[0:0] = [
      '/sample-buildout/eggs/zc.buildout-99.99-py2.4.egg',
      '/sample-buildout/eggs/setuptools-99.99-py2.4.egg',
      ]
    <BLANKLINE>
    import zc.buildout.buildout
    <BLANKLINE>
    if __name__ == '__main__':
        sys.exit(zc.buildout.buildout.main())

Now, let's recreate the sample buildout. If we specify constraints on
the versions of zc.buildout and setuptools to use, running the buildout
will install earlier versions of these packages:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... find-links = %(new_releases)s
    ... index = %(new_releases)s
    ... parts = show-versions
    ... develop = showversions
    ...
    ... [versions]
    ... zc.buildout = < 99
    ... setuptools = < 99
    ...
    ... [show-versions]
    ... recipe = showversions
    ... """ % dict(new_releases=new_releases))

Now we can see that we actually "upgrade" to an earlier version.

    >>> print_(system(buildout), end='')
    Upgraded:
      zc.buildout version 1.4.4;
      setuptools version 0.6;
    restarting.
    Generated script '/sample-buildout/bin/buildout'.
    Develop: '/sample-buildout/showversions'
    Updating show-versions.
    zc.buildout 1.0.0
    setuptools 0.6

There are a number of cases, described below, in which the updates
don't happen.

We won't upgrade in offline mode:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... find-links = %(new_releases)s
    ... index = %(new_releases)s
    ... parts = show-versions
    ... develop = showversions
    ...
    ... [show-versions]
    ... recipe = showversions
    ... """ % dict(new_releases=new_releases))

    >>> print_(system(buildout+' -o'), end='')
    Develop: '/sample-buildout/showversions'
    Updating show-versions.
    zc.buildout 1.0.0
    setuptools 0.6

Or in non-newest mode:

    >>> print_(system(buildout+' -N'), end='')
    Develop: '/sample-buildout/showversions'
    Updating show-versions.
    zc.buildout 1.0.0
    setuptools 0.6

We also won't upgrade if the buildout script being run isn't in the
buildouts bin directory.  To see this we'll create a new buildout
directory:

    >>> sample_buildout2 = tmpdir('sample_buildout2')
    >>> write(sample_buildout2, 'buildout.cfg',
    ... """
    ... [buildout]
    ... find-links = %(new_releases)s
    ... index = %(new_releases)s
    ... parts =
    ... """ % dict(new_releases=new_releases))

    >>> cd(sample_buildout2)
    >>> print_(system(buildout), end='')
    Creating directory '/sample_buildout2/eggs'.
    Creating directory '/sample_buildout2/bin'.
    Creating directory '/sample_buildout2/parts'.
    Creating directory '/sample_buildout2/develop-eggs'.
    Getting distribution for 'zc.buildout>=1.99'.
    Got zc.buildout 99.99.
    Getting distribution for 'setuptools'.
    Got setuptools 99.99.
    Not upgrading because not running a local buildout command.

    >>> ls('bin')

.. The relative-paths option is honored:

    >>> cd(sample_buildout)
    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... find-links = %(new_releases)s
    ... index = %(new_releases)s
    ... parts = show-versions
    ... develop = showversions
    ... relative-paths = true
    ...
    ... [show-versions]
    ... recipe = showversions
    ... """ % dict(new_releases=new_releases))

    >>> print_(system(buildout), end='')
    Upgraded:
      zc.buildout version 99.99,
      setuptools version 99.99;
    restarting.
    Generated script '/sample-buildout/bin/buildout'.
    Develop: '/sample-buildout/showversions'
    Unused options for buildout: 'relative-paths'.
    Updating show-versions.
    zc.buildout 99.99
    setuptools 99.99

    >>> cat('bin', 'buildout') # doctest +ELL
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import os
    <BLANKLINE>
    join = os.path.join
    base = os.path.dirname(os.path.abspath(os.path.realpath(__file__)))
    base = os.path.dirname(base)
    <BLANKLINE>
    import sys
    sys.path[0:0] = [
      join(base, 'eggs/zc.buildout-99.99-py3.3.egg'),
      join(base, 'eggs/setuptools-99.99-py3.3.egg'),
      ]
    <BLANKLINE>
    import zc.buildout.buildout
    <BLANKLINE>
    if __name__ == '__main__':
        sys.exit(zc.buildout.buildout.main())

When buildout restarts and the restarted buildout exits with an error code,
the original buildout that called the second buildout also exits with that
error code. Otherwise build scripts can erroneously detect a successful
buildout run even if it failed.

Make a recipe that fails:

    >>> mkdir(sample_buildout, 'failrecipe')
    >>> write(sample_buildout, 'failrecipe', 'failrecipe.py',
    ... """
    ... import pkg_resources
    ... import sys
    ... print_ = lambda *a: sys.stdout.write(' '.join(map(str, a))+'\\n')
    ...
    ... class Recipe:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         sys.exit('recipe sys-exits')
    ...
    ...     def install(self):
    ...         pass
    ...
    ...     update = install
    ... """)
    >>> write(sample_buildout, 'failrecipe', 'setup.py',
    ... """
    ... from setuptools import setup
    ...
    ... setup(
    ...     name = "failrecipe",
    ...     entry_points = {'zc.buildout': ['default = failrecipe:Recipe']},
    ...     )
    ... """)

Let's downgrade again, triggering a restart. And use the failing recipe that
gives us a sys.exit:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... find-links = %(new_releases)s
    ... index = %(new_releases)s
    ... parts = fail
    ... develop = failrecipe
    ...
    ... [versions]
    ... zc.buildout = < 99
    ... setuptools = < 99
    ...
    ... [fail]
    ... recipe = failrecipe
    ... """ % dict(new_releases=new_releases))

Run the buildout:

    >>> print_(system(buildout, with_exit_code=True), end='')
    Upgraded:
      zc.buildout version 1.4.4;
      setuptools version 0.6;
    restarting.
    Generated script '/sample-buildout/bin/buildout'.
    Develop: '/sample-buildout/failrecipe'
    recipe sys-exits
    EXIT CODE: 1

Debugging buildouts
===================

Buildouts can be pretty complex.  When things go wrong, it isn't
always obvious why.  Errors can occur due to problems in user input or
due to bugs in zc.buildout or recipes.  When an error occurs, Python's
post-mortem debugger can be used to inspect the state of the buildout
or recipe code were there error occurred.  To enable this, use the -D
option to the buildout.  Let's create a recipe that has a bug:

    >>> mkdir(sample_buildout, 'recipes')

    >>> write(sample_buildout, 'recipes', 'mkdir.py', 
    ... """
    ... import os, zc.buildout
    ...
    ... class Mkdir:
    ...
    ...     def __init__(self, buildout, name, options):
    ...         self.name, self.options = name, options
    ...         options['path'] = os.path.join(
    ...                               buildout['buildout']['directory'],
    ...                               options['path'],
    ...                               )
    ...
    ...     def install(self):
    ...         directory = self.options['directory']
    ...         os.mkdir(directory)
    ...         return directory
    ...
    ...     def update(self):
    ...         pass
    ... """)

    >>> write(sample_buildout, 'recipes', 'setup.py',
    ... """
    ... from setuptools import setup
    ... 
    ... setup(name = "recipes",
    ...       entry_points = {'zc.buildout': ['mkdir = mkdir:Mkdir']},
    ...       )
    ... """)

And create a buildout that uses it:

    >>> write(sample_buildout, 'buildout.cfg',
    ... """
    ... [buildout]
    ... develop = recipes
    ... parts = data-dir
    ...
    ... [data-dir]
    ... recipe = recipes:mkdir
    ... path = mystuff
    ... """)

If we run the buildout, we'll get an error:

    >>> print_(system(buildout), end='')
    Develop: '/sample-buildout/recipes'
    Installing data-dir.
    While:
      Installing data-dir.
    Error: Missing option: data-dir:directory


If we want to debug the error, we can add the -D option. Here's we'll
supply some input:

    >>> print_(system(buildout+" -D", """\
    ... up
    ... p sorted(self.options.keys())
    ... q
    ... """), end='')
    Develop: '/sample-buildout/recipes'
    Installing data-dir.
    > /zc/buildout/buildout.py(925)__getitem__()
    -> raise MissingOption("Missing option: %s:%s" % (self.name, key))
    (Pdb) > /sample-buildout/recipes/mkdir.py(14)install()
    -> directory = self.options['directory']
    (Pdb) ['path', 'recipe']
    (Pdb) While:
      Installing data-dir.
    Traceback (most recent call last):
      File "/zc/buildout/buildout.py", line 1352, in main
        getattr(buildout, command)(args)
      File "/zc/buildout/buildout.py", line 383, in install
        installed_files = self[part]._call(recipe.install)
      File "/zc/buildout/buildout.py", line 961, in _call
        return f()
      File "/sample-buildout/recipes/mkdir.py", line 14, in install
        directory = self.options['directory']
      File "/zc/buildout/buildout.py", line 925, in __getitem__
        raise MissingOption("Missing option: %s:%s" % (self.name, key))
    MissingOption: Missing option: data-dir:directory
    <BLANKLINE>
    Starting pdb:

Meta-recipe support
===================


Buildout recipes provide reusable Python modules for common
configuration tasks. The most widely used recipes tend to provide
low-level functions, like installing eggs or software distributions,
creating configuration files, and so on.  The normal recipe framework
is fairly well suited to building these general components.

Full-blown applications may require many, often tens, of parts.
Defining the many parts that make up an application can be tedious and
often entails a lot of repetition.  Buildout provides a number of
mechanisms to avoid repetition, including merging of configuration
files and macros, but these, while useful to an extent, don't scale
very well.  Buildout isn't and shouldn't be a programming language.

Meta-recipes allow us to bring Python to bear to provide higher-level
abstractions for buildouts.

A meta-recipe is a regular Python recipe that primarily operates by
creating parts.  A meta recipe isn't merely a high level recipe.  It's
a recipe that defers most or all of it's work to lower-level recipes by
manipulating the buildout database.

A `presentation at PyCon 2011
<http://blip.tv/pycon-us-videos-2009-2010-2011/pycon-2011-deploying-applications-with-zc-buildout-4897770>`_
described early work with meta recipes.

A simple meta-recipe example
============================

Let's look at a fairly simple meta-recipe example.  First, consider a
buildout configuration that builds a database deployment::

  [buildout]
  parts = ctl pack

  [deployment]
  recipe = zc.recipe.deployment
  name = ample
  user = zope

  [ctl]
  recipe = zc.recipe.rhrc
  deployment = deployment
  chkconfig = 345 99 10
  parts = main

  [main]
  recipe = zc.zodbrecipes:server
  deployment = deployment
  address = 8100
  path = /var/databases/ample/main.fs
  zeo.conf =
     <zeo>
        address ${:address}
     </zeo>
     %import zc.zlibstorage
     <zlibstorage>
       <filestorage>
          path ${:path}
       </filestorage>
     </zlibstorage>

  [pack]
  recipe = zc.recipe.deployment:crontab
  deployment = deployment
  times = 1 2 * * 6
  command = ${buildout:bin-directory}/zeopack -d3 -t00 ${main:address}

.. -> low_level

This buildout doesn't build software. Rather it builds configuration
for deploying a database configuration using already-deployed
software.  For the purpose of this document, however, the details are
totally unimportant.

Rather than crafting the configuration above every time, we can write
a meta-recipe that crafts it for us.  We'll use our meta-recipe as
follows::

  [buildout]
  parts = ample

  [ample]
  recipe = com.example.ample:db
  path = /var/databases/ample/main.fs

The idea here is that the meta recipe allows us to specify the minimal
information necessary.  A meta-recipe often automates policies and
assumptions that are application and organization dependent.  The
example above assumes, for example, that we want to pack to 3
days in the past on Saturdays.

So now, let's see the meta recipe that automates this::

  class Recipe:

      def __init__(self, buildout, name, options):

          buildout.parse('''
              [deployment]
              recipe = zc.recipe.deployment
              name = %s
              user = zope
              ''' % name)

          buildout['main'] = dict(
              recipe = 'zc.zodbrecipes:server',
              deployment = 'deployment',
              address = 8100,
              path = options['path'],
              **{
                'zeo.conf': '''
                  <zeo>
                    address ${:address}
                  </zeo>

                  %import zc.zlibstorage

                  <zlibstorage>
                    <filestorage>
                      path ${:path}
                    </filestorage>
                  </zlibstorage>
                  '''}
              )

          buildout.parse('''
              [pack]
              recipe = zc.recipe.deployment:crontab
              deployment = deployment
              times = 1 2 * * 6
              command =
                ${buildout:bin-directory}/zeopack -d3 -t00 ${main:address}

              [ctl]
              recipe = zc.recipe.rhrc
              deployment = deployment
              chkconfig = 345 99 10
              parts = main
              ''')

      def install(self):
          pass

      update = install

.. -> source

    >>> exec(source)

The meta recipe just adds parts to the buildout. It does this by
setting items and and calling the ``parse`` method.  The ``parse``
method just takes a string in buildout configuration syntax.  It's
useful when we want to add static, or nearly static part data.  The
setting items syntax is useful when we have non-trivial computation
for part data.

The order that we add parts is important.  When adding a part, any
string substitutions and other dependencies are evaluated, so the
referenced parts must be defined first.  This is why, for example, the
``pack`` part is added after the ``main`` part.

Note that the meta recipe supplied an integer for one of the
options. In addition to strings, it's legal to supply integer values.

There are a few things to note about this example:

- The install and update methods are empty.

  While not required, this is a very common pattern for meta
  recipes. Most meta recipes, simply invoke other recipes.

- Setting a buildout item or calling parse, adds any sections with
  recipes as parts.

- An exception will be raised if a section already exists.

Testing
-------

Now, let's test our meta recipe.  We'll test it without actually
running buildout. Rather, we'll use a specialized buildout provided by
the zc.buildout.testing module.

    >>> import zc.buildout.testing
    >>> buildout = zc.buildout.testing.Buildout()

The testing buildout is intended to be passed to recipes being
tested:

    >>> _ = Recipe(buildout, 'ample', dict(path='/var/databases/ample/main.fs'))

After running the recipe, we should see the buildout database
populated by the recipe:

    >>> buildout.print_options()
    [ctl]
    chkconfig = 345 99 10
    deployment = deployment
    parts = main
    recipe = zc.recipe.rhrc
    [deployment]
    name = ample
    recipe = zc.recipe.deployment
    user = zope
    [main]
    address = 8100
    deployment = deployment
    path = /var/databases/ample/main.fs
    recipe = zc.zodbrecipes:server
    zeo.conf =
    <BLANKLINE>
                      <zeo>
                        address 8100
                      </zeo>
    <BLANKLINE>
                      %import zc.zlibstorage
    <BLANKLINE>
                      <zlibstorage>
                        <filestorage>
                          path /var/databases/ample/main.fs
                        </filestorage>
                      </zlibstorage>
    <BLANKLINE>
    [pack]
    command = /sample-buildout/bin/zeopack -d3 -t00 8100
    deployment = deployment
    recipe = zc.recipe.deployment:crontab
    times = 1 2 * * 6

Testing Support
===============

The zc.buildout.testing module provides an API that can be used when
writing recipe tests.  This API is documented below.  Many examples of
using this API can be found in the zc.buildout, zc.recipe.egg, and
zc.recipe.testrunner tests.

zc.buildout.testing.buildoutSetUp(test)
---------------------------------------

The buildoutSetup function can be used as a doctest setup function.
It creates a sample buildout that can be used by tests, changing the
current working directory to the sample_buildout. It also adds a
number of names to the test namespace:

``sample_buildout``
    This is the name of a buildout with a basic configuration.

``buildout``
    This is the path of the buildout script in the sample buildout.

``ls(*path)``
    List the contents of a directory.  The directory path is provided as one or
    more strings, to be joined with os.path.join.

``cat(*path)``
    Display the contents of a file.   The file path is provided as one or
    more strings, to be joined with os.path.join.

    On Windows, if the file doesn't exist, the function will try
    adding a '-script.py' suffix.  This helps to work around a
    difference in script generation on windows.

``mkdir(*path)``
    Create a directory. The directory path is provided as one or
    more strings, to be joined with os.path.join.

``rmdir(*path)``
    Remove a directory. The directory path is provided as one or
    more strings, to be joined with os.path.join.

``remove(*path)``
    Remove a directory or file. The path is provided as one or
    more strings, to be joined with os.path.join.

``tmpdir(name)``
    Create a temporary directory with the given name.  The directory
    will be automatically removed at the end of the test.  The path of
    the created directory is returned.

    Further, if the the normalize_path normalizing substitution (see
    below) is used, then any paths starting with this path will be
    normalized to::

      /name/restofpath

    No two temporary directories can be created with the same name.  A
    directory created with tmpdir can be removed with rmdir and recreated.

    Note that the sample_buildout directory is created by calling this
    function.

``write(*path_and_contents)``
    Create a file.  The file path is provided as one or more strings,
    to be joined with os.path.join. The last argument is the file contents.

``system(command, input='')``
    Execute a system command with the given input passed to the
    command's standard input.  The output (error and regular output)
    from the command is returned.

``get(url)``
    Get a web page.

``cd(*path)``
    Change to the given directory.  The directory path is provided as one or
    more strings, to be joined with os.path.join.

    The directory will be reset at the end of the test.

``uncd()``
    Change to the directory that was current prior to the previous
    call to ``cd``. You can call ``cd`` multiple times and then
    ``uncd`` the same number of times to return to the same location.

``join(*path)``
    A convenient reference to os.path.join.

``register_teardown(func)``
    Register a tear-down function.  The function will be called with
    no arguments at the end of the test.

``start_server(path)``
    Start a web server on the given path.  The server will be shut
    down at the end of the test.  The server URL is returned.

    You can cause the server to start and stop logging it's output
    using: 

       >>> get(server_url+'enable_server_logging')

    and:

       >>> get(server_url+'disable_server_logging')

    This can be useful to see how buildout is interacting with a
    server.


``sdist(setup, dest)``
    Create a source distribution by running the given setup file and
    placing the result in the given destination directory.  If the
    setup argument is a directory, the setup.py file in that
    directory is used.

``bdist_egg(setup, dest)``
    Create an egg by running the given setup file
    and placing the result in the given destination
    directory.  If the setup argument is a directory, then the
    setup.py file in that directory is used.

``zc.buildout.testing.buildoutTearDown(test)``
----------------------------------------------

Tear down everything set up by zc.buildout.testing.buildoutSetUp.  Any
functions passed to register_teardown are called as well.

``install(project, destination)``
---------------------------------

Install eggs for a given project into a destination.  If the
destination is a test object, then the eggs directory of the
sample buildout (sample_buildout) defined by the test will be used.
Tests will use this to install the distributions for the packages
being tested (and their dependencies) into a sample buildout. The egg
to be used should already be loaded, by importing one of the modules
provided, before calling this function.

``install_develop(project, destination)``
-----------------------------------------

Like install, but a develop egg is installed even if the current egg
if not a develop egg.

``Output normalization``
------------------------

Recipe tests often generate output that is dependent on temporary file
locations, operating system conventions or Python versions.  To deal
with these dependencies, we often use
zope.testing.renormalizing.RENormalizing to normalize test output.
zope.testing.renormalizing.RENormalizing takes pairs of regular
expressions and substitutions. The zc.buildout.testing module provides
a few helpful variables that define regular-expression/substitution
pairs that you can pass to zope.testing.renormalizing.RENormalizing.


``normalize_path``
   Converts tests paths, based on directories created with tmpdir(),
   to simple paths.

``normalize_script``
   On Unix-like systems, scripts are implemented in single files
   without suffixes.  On windows, scripts are implemented with 2
   files, a -script.py file and a .exe file.  This normalization
   converts directory listings of Windows scripts to the form
   generated on UNix-like systems.

``normalize_egg_py``
   Normalize Python version and platform indicators, if specified, in
   egg names.

Python API for egg and script installation
==========================================

The easy_install module provides some functions to provide support for
egg and script installation.  It provides functionality at the python
level that is similar to easy_install, with a few exceptions:

- By default, we look for new packages *and* the packages that
  they depend on.  This is somewhat like (and uses) the --upgrade
  option of easy_install, except that we also upgrade required
  packages.

- If the highest-revision package satisfying a specification is
  already present, then we don't try to get another one.  This saves a
  lot of search time in the common case that packages are pegged to
  specific versions.

- If there is a develop egg that satisfies a requirement, we don't
  look for additional distributions.  We always give preference to
  develop eggs.

- Distutils options for building extensions can be passed.

Distribution installation
-------------------------

The easy_install module provides a function, install, for installing one
or more packages and their dependencies.  The install function takes 2
positional arguments:

- An iterable of setuptools requirement strings for the distributions
  to be installed, and

- A destination directory to install to and to satisfy requirements
  from.  The destination directory can be None, in which case, no new
  distributions are downloaded and there will be an error if the
  needed distributions can't be found among those already installed.

It supports a number of optional keyword arguments:

links
   A sequence of URLs, file names, or directories to look for
   links to distributions.

index
   The URL of an index server, or almost any other valid URL. :)

   If not specified, the Python Package Index,
   http://pypi.python.org/simple/, is used.  You can specify an
   alternate index with this option.  If you use the links option and
   if the links point to the needed distributions, then the index can
   be anything and will be largely ignored.  In the examples, here,
   we'll just point to an empty directory on our link server.  This
   will make our examples run a little bit faster.

path
   A list of additional directories to search for locally-installed
   distributions.

working_set
   An existing working set to be augmented with additional
   distributions, if necessary to satisfy requirements.  This allows
   you to call install multiple times, if necessary, to gather
   multiple sets of requirements.

newest
   A boolean value indicating whether to search for new distributions
   when already-installed distributions meet the requirement.  When
   this is true, the default, and when the destination directory is
   not None, then the install function will search for the newest
   distributions that satisfy the requirements.

versions
   A dictionary mapping project names to version numbers to be used
   when selecting distributions.  This can be used to specify a set of
   distribution versions independent of other requirements.

use_dependency_links
   A flag indicating whether to search for dependencies using the
   setup dependency_links metadata or not. If true, links are searched
   for using dependency_links in preference to other
   locations. Defaults to true.

relative_paths
   Adjust egg paths so they are relative to the script path.  This
   allows scripts to work when scripts and eggs are moved, as long as
   they are both moved in the same way.

The install method returns a working set containing the distributions
needed to meet the given requirements.

We have a link server that has a number of eggs:

    >>> print_(get(link_server), end='')
    <html><body>
    <a href="bigdemo-0.1-py2.4.egg">bigdemo-0.1-py2.4.egg</a><br>
    <a href="demo-0.1-py2.4.egg">demo-0.1-py2.4.egg</a><br>
    <a href="demo-0.2-py2.4.egg">demo-0.2-py2.4.egg</a><br>
    <a href="demo-0.3-py2.4.egg">demo-0.3-py2.4.egg</a><br>
    <a href="demo-0.4rc1-py2.4.egg">demo-0.4rc1-py2.4.egg</a><br>
    <a href="demoneeded-1.0.zip">demoneeded-1.0.zip</a><br>
    <a href="demoneeded-1.1.zip">demoneeded-1.1.zip</a><br>
    <a href="demoneeded-1.2rc1.zip">demoneeded-1.2rc1.zip</a><br>
    <a href="du_zipped-1.0-pyN.N.egg">du_zipped-1.0-pyN.N.egg</a><br>
    <a href="extdemo-1.4.zip">extdemo-1.4.zip</a><br>
    <a href="index/">index/</a><br>
    <a href="other-1.0-py2.4.egg">other-1.0-py2.4.egg</a><br>
    </body></html>

Let's make a directory and install the demo egg to it, using the demo:

    >>> dest = tmpdir('sample-install')
    >>> import zc.buildout.easy_install
    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo==0.2'], dest,
    ...     links=[link_server], index=link_server+'index/')

We requested version 0.2 of the demo distribution to be installed into
the destination server.  We specified that we should search for links
on the link server and that we should use the (empty) link server
index directory as a package index.

The working set contains the distributions we retrieved.

    >>> for dist in ws:
    ...     print_(dist)
    demo 0.2
    demoneeded 1.1

We got demoneeded because it was a dependency of demo.

And the actual eggs were added to the eggs directory.

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demoneeded-1.1-py2.4.egg

If we remove the version restriction on demo, but specify a false
value for newest, no new distributions will be installed:

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest, links=[link_server], index=link_server+'index/',
    ...     newest=False)
    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demoneeded-1.1-py2.4.egg

If we leave off the newest option, we'll get an update for demo:

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest, links=[link_server], index=link_server+'index/')
    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demo-0.3-py2.4.egg
    d  demoneeded-1.1-py2.4.egg

Note that we didn't get the newest versions available.  There were
release candidates for newer versions of both packages. By default,
final releases are preferred.  We can change this behavior using the
prefer_final function:

    >>> zc.buildout.easy_install.prefer_final(False)
    True

The old setting is returned.

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest, links=[link_server], index=link_server+'index/')
    >>> for dist in ws:
    ...     print_(dist)
    demo 0.4rc1
    demoneeded 1.2rc1

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demo-0.3-py2.4.egg
    d  demo-0.4rc1-py2.4.egg
    d  demoneeded-1.1-py2.4.egg
    d  demoneeded-1.2rc1-py2.4.egg

Let's put the setting back to the default.

    >>> zc.buildout.easy_install.prefer_final(True)
    False

We can supply additional distributions.  We can also supply
specifications for distributions that would normally be found via
dependencies.  We might do this to specify a specific version.

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo', 'other', 'demoneeded==1.0'], dest,
    ...     links=[link_server], index=link_server+'index/')

    >>> for dist in ws:
    ...     print_(dist)
    demo 0.3
    other 1.0
    demoneeded 1.0

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demo-0.3-py2.4.egg
    d  demo-0.4rc1-py2.4.egg
    d  demoneeded-1.0-py2.4.egg
    d  demoneeded-1.1-py2.4.egg
    d  demoneeded-1.2rc1-py2.4.egg
    d  other-1.0-py2.4.egg

    >>> rmdir(dest)

Specifying version information independent of requirements
----------------------------------------------------------

Sometimes it's useful to specify version information independent of
normal requirements specifications.  For example, a buildout may need
to lock down a set of versions, without having to put put version
numbers in setup files or part definitions.  If a dictionary is passed
to the install function, mapping project names to version numbers,
then the versions numbers will be used.

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest, links=[link_server], index=link_server+'index/',
    ...     versions = dict(demo='0.2', demoneeded='1.0'))
    >>> [d.version for d in ws]
    ['0.2', '1.0']

In this example, we specified a version for demoneeded, even though we
didn't define a requirement for it.  The versions specified apply to
dependencies as well as the specified requirements.

If we specify a version that's incompatible with a requirement, then
we'll get an error:

    >>> from zope.testing.loggingsupport import InstalledHandler
    >>> handler = InstalledHandler('zc.buildout.easy_install')
    >>> import logging
    >>> logging.getLogger('zc.buildout.easy_install').propagate = False

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo >0.2'], dest, links=[link_server],
    ...     index=link_server+'index/',
    ...     versions = dict(demo='0.2', demoneeded='1.0'))
    Traceback (most recent call last):
    ...
    IncompatibleConstraintError: Bad constraint 0.2 demo>0.2

    >>> print_(handler)
    zc.buildout.easy_install DEBUG
      Installing 'demo >0.2'.
    zc.buildout.easy_install ERROR
      The constraint, 0.2, is not consistent with the requirement, 'demo>0.2'.

    >>> handler.clear()

If no versions are specified, a debugging message will be output
reporting that a version was picked automatically:

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest, links=[link_server], index=link_server+'index/',
    ...     )

    >>> print_(handler) # doctest: +ELLIPSIS
    zc.buildout.easy_install DEBUG
      Installing 'demo'.
    zc.buildout.easy_install INFO
      Getting distribution for 'demo'.
    zc.buildout.easy_install INFO
      Got demo 0.3.
    zc.buildout.easy_install DEBUG
      Picked: demo = 0.3
    zc.buildout.easy_install DEBUG
      Getting required 'demoneeded'
    zc.buildout.easy_install DEBUG
        required by demo 0.3.
    zc.buildout.easy_install INFO
      Getting distribution for 'demoneeded'.
    zc.buildout.easy_install DEBUG
      Running easy_install:...
    zc.buildout.easy_install INFO
      Got demoneeded 1.1.
    zc.buildout.easy_install DEBUG
      Picked: demoneeded = 1.1


    zc.buildout.easy_install DEBUG
      Installing 'demo'.
    zc.buildout.easy_install DEBUG
      We have the best distribution that satisfies 'demo'.
    zc.buildout.easy_install DEBUG
      Picked: demo = 0.3
    zc.buildout.easy_install DEBUG
      Getting required 'demoneeded'
    zc.buildout.easy_install DEBUG
        required by demo 0.3.
    zc.buildout.easy_install DEBUG
      We have the best distribution that satisfies 'demoneeded'.
    zc.buildout.easy_install DEBUG
      Picked: demoneeded = 1.1

    >>> handler.uninstall()
    >>> logging.getLogger('zc.buildout.easy_install').propagate = True

We can request that we get an error if versions are picked:

    >>> zc.buildout.easy_install.allow_picked_versions(False)
    True

(The old setting is returned.)

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest, links=[link_server], index=link_server+'index/',
    ...     )
    Traceback (most recent call last):
    ...
    UserError: Picked: demo = 0.3

    >>> zc.buildout.easy_install.allow_picked_versions(True)
    False

The function default_versions can be used to get and set default
version information to be used when no version information is passes.
If called with an argument, it sets the default versions:

    >>> zc.buildout.easy_install.default_versions(dict(demoneeded='1'))
    ... # doctest: +ELLIPSIS
    {...}

It always returns the previous default versions.  If called without an
argument, it simply returns the default versions without changing
them:

    >>> zc.buildout.easy_install.default_versions()
    {'demoneeded': '1'}

So with the default versions set, we'll get the requested version even
if the versions option isn't used:

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest, links=[link_server], index=link_server+'index/',
    ...     )

    >>> [d.version for d in ws]
    ['0.3', '1.0']

Of course, we can unset the default versions by passing an empty
dictionary:

    >>> zc.buildout.easy_install.default_versions({})
    {'demoneeded': '1'}

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest, links=[link_server], index=link_server+'index/',
    ...     )

    >>> [d.version for d in ws]
    ['0.3', '1.1']

Dependency links
----------------

Setuptools allows metadata that describes where to search for package
dependencies. This option is called dependency_links. Buildout has its
own notion of where to look for dependencies, but it also uses the
setup tools dependency_links information if it's available.

Let's demo this by creating an egg that specifies dependency_links.

To begin, let's create a new egg repository. This repository hold a
newer version of the 'demoneeded' egg than the sample repository does.

    >>> repoloc = tmpdir('repo')
    >>> from zc.buildout.tests import create_egg
    >>> create_egg('demoneeded', '1.2', repoloc)
    >>> link_server2 = start_server(repoloc)

Turn on logging on this server so that we can see when eggs are pulled
from it.

    >>> _ = get(link_server2 + 'enable_server_logging')
    GET 200 /enable_server_logging

Now we can create an egg that specifies that its dependencies are
found on this server.

    >>> repoloc = tmpdir('repo2')
    >>> create_egg('hasdeps', '1.0', repoloc,
    ...            install_requires = "'demoneeded'",
    ...            dependency_links = [link_server2])

Let's add the egg to another repository.

    >>> link_server3 = start_server(repoloc)

Now let's install the egg.

    >>> example_dest = tmpdir('example-install')
    >>> workingset = zc.buildout.easy_install.install(
    ...     ['hasdeps'], example_dest,
    ...     links=[link_server3], index=link_server3+'index/')
    GET 200 /
    GET 200 /demoneeded-1.2-pyN.N.egg

The server logs show that the dependency was retrieved from the server
specified in the dependency_links.

Now let's see what happens if we provide two different ways to retrieve
the dependencies.

    >>> rmdir(example_dest)
    >>> example_dest = tmpdir('example-install')
    >>> workingset = zc.buildout.easy_install.install(
    ...     ['hasdeps'], example_dest, index=link_server+'index/',
    ...     links=[link_server, link_server3])
    GET 200 /
    GET 200 /demoneeded-1.2-pyN.N.egg

Once again the dependency is fetched from the logging server even
though it is also available from the non-logging server. This is
because the version on the logging server is newer and buildout
normally chooses the newest egg available.

If you wish to control where dependencies come from regardless of
dependency_links setup metadata use the 'use_dependency_links' option
to zc.buildout.easy_install.install().

    >>> rmdir(example_dest)
    >>> example_dest = tmpdir('example-install')
    >>> workingset = zc.buildout.easy_install.install(
    ...     ['hasdeps'], example_dest, index=link_server+'index/',
    ...     links=[link_server, link_server3],
    ...     use_dependency_links=False)

Notice that this time the dependency egg is not fetched from the
logging server. When you specify not to use dependency_links, eggs
will only be searched for using the links you explicitly provide.

Another way to control this option is with the
zc.buildout.easy_install.use_dependency_links() function. This
function sets the default behavior for the zc.buildout.easy_install()
function.

    >>> zc.buildout.easy_install.use_dependency_links(False)
    True

The function returns its previous setting.

    >>> rmdir(example_dest)
    >>> example_dest = tmpdir('example-install')
    >>> workingset = zc.buildout.easy_install.install(
    ...     ['hasdeps'], example_dest, index=link_server+'index/',
    ...     links=[link_server, link_server3])

It can be overridden by passing a keyword argument to the install
function.

    >>> rmdir(example_dest)
    >>> example_dest = tmpdir('example-install')
    >>> workingset = zc.buildout.easy_install.install(
    ...     ['hasdeps'], example_dest, index=link_server+'index/',
    ...     links=[link_server, link_server3],
    ...	    use_dependency_links=True)
    GET 200 /demoneeded-1.2-pyN.N.egg

To return the dependency_links behavior to normal call the function again.

    >>> zc.buildout.easy_install.use_dependency_links(True)
    False
    >>> rmdir(example_dest)
    >>> example_dest = tmpdir('example-install')
    >>> workingset = zc.buildout.easy_install.install(
    ...     ['hasdeps'], example_dest, index=link_server+'index/',
    ...     links=[link_server, link_server3])
    GET 200 /demoneeded-1.2-pyN.N.egg


Script generation
-----------------

The easy_install module provides support for creating scripts from
eggs.  It provides a function similar to setuptools except that it
provides facilities for baking a script's path into the script.  This
has two advantages:

- The eggs to be used by a script are not chosen at run time, making
  startup faster and, more importantly, deterministic.

- The script doesn't have to import pkg_resources because the logic
  that pkg_resources would execute at run time is executed at
  script-creation time.

The scripts method can be used to generate scripts. Let's create a
destination directory for it to place them in:

    >>> import tempfile
    >>> bin = tmpdir('bin')

Now, we'll use the scripts method to generate scripts in this directory
from the demo egg:

    >>> import sys
    >>> scripts = zc.buildout.easy_install.scripts(
    ...     ['demo'], ws, sys.executable, bin)

the three arguments we passed were:

1. A sequence of distribution requirements.  These are of the same
   form as setuptools requirements.  Here we passed a single
   requirement, for the version 0.1 demo distribution.

2. A working set,

3. The destination directory.

The bin directory now contains a generated script:

    >>> ls(bin)
    -  demo

The return value is a list of the scripts generated:

    >>> import os, sys
    >>> if sys.platform == 'win32':
    ...     scripts == [os.path.join(bin, 'demo.exe'),
    ...                 os.path.join(bin, 'demo-script.py')]
    ... else:
    ...     scripts == [os.path.join(bin, 'demo')]
    True

Note that in Windows, 2 files are generated for each script.  A script
file, ending in '-script.py', and an exe file that allows the script
to be invoked directly without having to specify the Python
interpreter and without having to provide a '.py' suffix.

The demo script run the entry point defined in the demo egg:

    >>> cat(bin, 'demo') # doctest: +NORMALIZE_WHITESPACE
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import sys
    sys.path[0:0] = [
      '/sample-install/demo-0.3-py2.4.egg',
      '/sample-install/demoneeded-1.1-py2.4.egg',
      ]
    <BLANKLINE>
    import eggrecipedemo
    <BLANKLINE>
    if __name__ == '__main__':
        sys.exit(eggrecipedemo.main())

Some things to note:

- The demo and demoneeded eggs are added to the beginning of sys.path.

- The module for the script entry point is imported and the entry
  point, in this case, 'main', is run.

Rather than requirement strings, you can pass tuples containing 3
strings:

  - A script name,

  - A module,

  - An attribute expression for an entry point within the module.

For example, we could have passed entry point information directly
rather than passing a requirement:

    >>> scripts = zc.buildout.easy_install.scripts(
    ...     [('demo', 'eggrecipedemo', 'main')], ws,
    ...     sys.executable, bin)

    >>> cat(bin, 'demo') # doctest: +NORMALIZE_WHITESPACE
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import sys
    sys.path[0:0] = [
      '/sample-install/demo-0.3-py2.4.egg',
      '/sample-install/demoneeded-1.1-py2.4.egg',
      ]
    <BLANKLINE>
    import eggrecipedemo
    <BLANKLINE>
    if __name__ == '__main__':
        sys.exit(eggrecipedemo.main())

Passing entry-point information directly is handy when using eggs (or
distributions) that don't declare their entry points, such as
distributions that aren't based on setuptools.

The interpreter keyword argument can be used to generate a script that can
be used to invoke the Python interactive interpreter with the path set
based on the working set.  This generated script can also be used to
run other scripts with the path set on the working set:

    >>> scripts = zc.buildout.easy_install.scripts(
    ...     ['demo'], ws, sys.executable, bin, interpreter='py')


    >>> ls(bin)
    -  demo
    -  py

    >>> if sys.platform == 'win32':
    ...     scripts == [os.path.join(bin, 'demo.exe'),
    ...                 os.path.join(bin, 'demo-script.py'),
    ...                 os.path.join(bin, 'py.exe'),
    ...                 os.path.join(bin, 'py-script.py')]
    ... else:
    ...     scripts == [os.path.join(bin, 'demo'),
    ...                 os.path.join(bin, 'py')]
    True

The py script simply runs the Python interactive interpreter with
the path set:

    >>> cat(bin, 'py') # doctest: +NORMALIZE_WHITESPACE +REPORT_NDIFF
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import sys
    <BLANKLINE>
    sys.path[0:0] = [
      '/sample-install/demo-0.3-pyN.N.egg',
      '/sample-install/demoneeded-1.1-pyN.N.egg',
      ]
    <BLANKLINE>
    _interactive = True
    if len(sys.argv) > 1:
        _options, _args = __import__("getopt").getopt(sys.argv[1:], 'ic:m:')
        _interactive = False
        for (_opt, _val) in _options:
            if _opt == '-i':
                _interactive = True
            elif _opt == '-c':
                exec(_val)
            elif _opt == '-m':
                sys.argv[1:] = _args
                _args = []
                __import__("runpy").run_module(
                     _val, {}, "__main__", alter_sys=True)
    <BLANKLINE>
        if _args:
            sys.argv[:] = _args
            __file__ = _args[0]
            del _options, _args
            with open(__file__, 'U') as __file__f:
                exec(compile(__file__f.read(), __file__, "exec"))
    <BLANKLINE>
    if _interactive:
        del _interactive
        __import__("code").interact(banner="", local=globals())

If invoked with a script name and arguments, it will run that script, instead.

    >>> write('ascript', r'''
    ... "demo doc"
    ... import sys
    ... print_ = lambda *a: sys.stdout.write(' '.join(map(str, a))+'\n')
    ... print_(sys.argv)
    ... print_((__name__, __file__, __doc__))
    ... ''')
    >>> print_(system(join(bin, 'py')+' ascript a b c'), end='')
    ['ascript', 'a', 'b', 'c']
    ('__main__', 'ascript', 'demo doc')

For Python 2.5 and higher, you can also use the -m option to run a
module:

    >>> if sys.version_info < (2, 5):
    ...    print ('usage: pdb.py blah blah blah')
    ... else:
    ...    print_(system(join(bin, 'py')+' -m pdb'), end='')
    ... # doctest: +ELLIPSIS
    usage: pdb.py ...

    >>> print_(system(join(bin, 'py')+' -m pdb what'), end='')
    Error: what does not exist

An interpreter can also be generated without other eggs:

    >>> scripts = zc.buildout.easy_install.scripts(
    ...     [], [], sys.executable, bin, interpreter='py')
    >>> cat(bin, 'py') # doctest: +NORMALIZE_WHITESPACE +ELLIPSIS
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import sys
    <BLANKLINE>
    sys.path[0:0] = [
    <BLANKLINE>
      ]
    ...

An additional argument can be passed to define which scripts to install
and to provide script names. The argument is a dictionary mapping
original script names to new script names.

    >>> bin = tmpdir('bin2')
    >>> scripts = zc.buildout.easy_install.scripts(
    ...     ['demo'], ws, sys.executable, bin, dict(demo='run'))

    >>> if sys.platform == 'win32':
    ...     scripts == [os.path.join(bin, 'run.exe'),
    ...                 os.path.join(bin, 'run-script.py')]
    ... else:
    ...     scripts == [os.path.join(bin, 'run')]
    True
    >>> ls(bin)
    -  run

    >>> print_(system(os.path.join(bin, 'run')), end='')
    3 1

The scripts that are generated are made executable:

    >>> if sys.platform == 'win32':
    ...     os.access(os.path.join(bin, 'run.exe'), os.X_OK)
    ... else:
    ...     os.access(os.path.join(bin, 'run'), os.X_OK)
    True


Including extra paths in scripts
--------------------------------

We can pass a keyword argument, extra paths, to cause additional paths
to be included in the a generated script:

    >>> foo = tmpdir('foo')
    >>> scripts = zc.buildout.easy_install.scripts(
    ...    ['demo'], ws, sys.executable, bin, dict(demo='run'),
    ...    extra_paths=[foo])

    >>> cat(bin, 'run') # doctest: +NORMALIZE_WHITESPACE
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import sys
    sys.path[0:0] = [
      '/sample-install/demo-0.3-py2.4.egg',
      '/sample-install/demoneeded-1.1-py2.4.egg',
      '/foo',
      ]
    <BLANKLINE>
    import eggrecipedemo
    <BLANKLINE>
    if __name__ == '__main__':
        sys.exit(eggrecipedemo.main())

Providing script arguments
--------------------------

An "argument" keyword argument can be used to pass arguments to an
entry point.  The value passed is a source string to be placed between the
parentheses in the call:

    >>> scripts = zc.buildout.easy_install.scripts(
    ...    ['demo'], ws, sys.executable, bin, dict(demo='run'),
    ...    arguments='1, 2')

    >>> cat(bin, 'run') # doctest: +NORMALIZE_WHITESPACE
    #!/usr/local/bin/python2.7
    import sys
    sys.path[0:0] = [
      '/sample-install/demo-0.3-py2.4.egg',
      '/sample-install/demoneeded-1.1-py2.4.egg',
      ]
    <BLANKLINE>
    import eggrecipedemo
    <BLANKLINE>
    if __name__ == '__main__':
        sys.exit(eggrecipedemo.main(1, 2))

Passing initialization code
---------------------------

You can also pass script initialization code:

    >>> scripts = zc.buildout.easy_install.scripts(
    ...    ['demo'], ws, sys.executable, bin, dict(demo='run'),
    ...    arguments='1, 2',
    ...    initialization='import os\nos.chdir("foo")',
    ...    interpreter='py')

    >>> cat(bin, 'run') # doctest: +NORMALIZE_WHITESPACE
    #!/usr/local/bin/python2.7
    import sys
    sys.path[0:0] = [
      '/sample-install/demo-0.3-py2.4.egg',
      '/sample-install/demoneeded-1.1-py2.4.egg',
      ]
    <BLANKLINE>
    import os
    os.chdir("foo")
    <BLANKLINE>
    import eggrecipedemo
    <BLANKLINE>
    if __name__ == '__main__':
        sys.exit(eggrecipedemo.main(1, 2))

It will be included in interpreters too:

    >>> cat(bin, 'py') # doctest: +NORMALIZE_WHITESPACE +ELLIPSIS
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import sys
    <BLANKLINE>
    sys.path[0:0] = [
      '/sample-install/demo-0.3-py3.3.egg',
      '/sample-install/demoneeded-1.1-py3.3.egg',
      ]
    <BLANKLINE>
    import os
    os.chdir("foo")
    <BLANKLINE>
    <BLANKLINE>
    _interactive = True
    ...

Relative paths
--------------

Sometimes, you want to be able to move a buildout directory around and
have scripts still work without having to rebuild them.  We can
control this using the relative_paths option to install.  You need
to pass a common base directory of the scripts and eggs:

    >>> bo = tmpdir('bo')
    >>> ba = tmpdir('ba')
    >>> mkdir(bo, 'eggs')
    >>> mkdir(bo, 'bin')
    >>> mkdir(bo, 'other')

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], join(bo, 'eggs'), links=[link_server],
    ...     index=link_server+'index/')

    >>> scripts = zc.buildout.easy_install.scripts(
    ...    ['demo'], ws, sys.executable, join(bo, 'bin'), dict(demo='run'),
    ...    extra_paths=[ba, join(bo, 'bar')],
    ...    interpreter='py',
    ...    relative_paths=bo)

    >>> cat(bo, 'bin', 'run')
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import os
    <BLANKLINE>
    join = os.path.join
    base = os.path.dirname(os.path.abspath(os.path.realpath(__file__)))
    base = os.path.dirname(base)
    <BLANKLINE>
    import sys
    sys.path[0:0] = [
      join(base, 'eggs/demo-0.3-pyN.N.egg'),
      join(base, 'eggs/demoneeded-1.1-pyN.N.egg'),
      '/ba',
      join(base, 'bar'),
      ]
    <BLANKLINE>
    import eggrecipedemo
    <BLANKLINE>
    if __name__ == '__main__':
        sys.exit(eggrecipedemo.main())

Note that the extra path we specified that was outside the directory
passed as relative_paths wasn't converted to a relative path.

Of course, running the script works:

    >>> print_(system(join(bo, 'bin', 'run')), end='')
    3 1

We specified an interpreter and its paths are adjusted too:

    >>> cat(bo, 'bin', 'py') # doctest: +NORMALIZE_WHITESPACE +REPORT_NDIFF
    #!/usr/local/bin/python2.7
    <BLANKLINE>
    import os
    <BLANKLINE>
    join = os.path.join
    base = os.path.dirname(os.path.abspath(os.path.realpath(__file__)))
    base = os.path.dirname(base)
    <BLANKLINE>
    import sys
    <BLANKLINE>
    sys.path[0:0] = [
      join(base, 'eggs/demo-0.3-pyN.N.egg'),
      join(base, 'eggs/demoneeded-1.1-pyN.N.egg'),
      '/ba',
      join(base, 'bar'),
      ]
    <BLANKLINE>
    _interactive = True
    if len(sys.argv) > 1:
        _options, _args = __import__("getopt").getopt(sys.argv[1:], 'ic:m:')
        _interactive = False
        for (_opt, _val) in _options:
            if _opt == '-i':
                _interactive = True
            elif _opt == '-c':
                exec(_val)
            elif _opt == '-m':
                sys.argv[1:] = _args
                _args = []
                __import__("runpy").run_module(
                     _val, {}, "__main__", alter_sys=True)
    <BLANKLINE>
        if _args:
            sys.argv[:] = _args
            __file__ = _args[0]
            del _options, _args
            with open(__file__, 'U') as __file__f:
                exec(compile(__file__f.read(), __file__, "exec"))
    <BLANKLINE>
    if _interactive:
        del _interactive
        __import__("code").interact(banner="", local=globals())


Installing distutils-style scripts
----------------------------------

Most python libraries use the console_scripts entry point nowadays.  But
several still have a ``scripts=['bin/something']`` in their setup() call.
Buildout also installs those:

    >>> distdir = tmpdir('distutilsscriptdir')
    >>> distbin = tmpdir('distutilsscriptbin')
    >>> ws = zc.buildout.easy_install.install(
    ...     ['other'], distdir,
    ...     links=[link_server], index=link_server+'index/')
    >>> scripts = zc.buildout.easy_install.scripts(
    ...     ['other'], ws, sys.executable, distbin)
    >>> ls(distbin)
    -  distutilsscript

Like for console_scripts, the output is a list of the scripts
generated. Likewise, on windows two files, an ``.exe`` and a script with
``-script.py`` appended, are generated:

    >>> import os, sys
    >>> if sys.platform == 'win32':
    ...     scripts == [os.path.join(distbin, 'distutilsscript.exe'),
    ...                 os.path.join(distbin, 'distutilsscript-script.py')]
    ... else:
    ...     scripts == [os.path.join(distbin, 'distutilsscript')]
    True

It also works for zipped eggs:

    >>> distdir2 = tmpdir('distutilsscriptdir2')
    >>> distbin2 = tmpdir('distutilsscriptbin2')
    >>> ws = zc.buildout.easy_install.install(
    ...     ['du_zipped'], distdir2,
    ...     links=[link_server], index=link_server+'index/')
    >>> scripts = zc.buildout.easy_install.scripts(
    ...     ['du_zipped'], ws, sys.executable, distbin2)
    >>> ls(distbin2)
    -  distutilsscript

Distutils copies the script files verbatim, apart from a line at the top that
looks like ``#!/usr/bin/python``, which gets replaced by the actual python
interpreter. Buildout does the same, but additionally also adds the sys.path
like for the console_scripts.

    >>> cat(distbin, 'distutilsscript')
    #!/usr/local/bin/python2.7
    # -*- coding: utf-8 -*-
    """Module docstring."""
    from __future__ import print_statement
    <BLANKLINE>
    <BLANKLINE>
    import sys
    sys.path[0:0] = [
      '/distutilsscriptdir/other-1.0-pyN.N.egg',
      ]
    <BLANKLINE>
    <BLANKLINE>
    import os
    import sys; sys.stdout.write("distutils!\n")

Note that there are several items that need to come first in such a script
*before* buildout's ``sys.path`` statements: a source encoding hint, a module
docstring and ``__future__`` imports. Buildout retains them in their proper
place by looking at the first non-future import and placing its ``sys.path``
statement before that.

Due to the nature of distutils scripts, buildout cannot pass arguments as
there's no specific method to pass them to.

In some cases, a python 3 ``__pycache__`` directory can end up in an internal
``EGG-INFO`` metadata directory, next to the script information we're looking
for. Buildout doesn't crash on that:

    >>> eggname = [name for name in os.listdir(distdir2)
    ...            if name.endswith('egg')][0]
    >>> scripts_metadata_dir = os.path.join(
    ...     distdir2, eggname, 'EGG-INFO', 'scripts')
    >>> os.mkdir(os.path.join(scripts_metadata_dir, '__dummy__'))
    >>> scripts = zc.buildout.easy_install.scripts(
    ...     ['du_zipped'], ws, sys.executable, distbin2)
    >>> ls(distbin2)
    -  distutilsscript


Handling custom build options for extensions provided in source distributions
-----------------------------------------------------------------------------

Sometimes, we need to control how extension modules are built.  The
build function provides this level of control.  It takes a single
package specification, downloads a source distribution, and builds it
with specified custom build options.

The build function takes 3 positional arguments:

spec
   A package specification for a source distribution

dest
   A destination directory

build_ext
   A dictionary of options to be passed to the distutils build_ext
   command when building extensions.

It supports a number of optional keyword arguments:

links
   a sequence of URLs, file names, or directories to look for
   links to distributions,

index
   The URL of an index server, or almost any other valid URL. :)

   If not specified, the Python Package Index,
   http://pypi.python.org/simple/, is used.  You can specify an
   alternate index with this option.  If you use the links option and
   if the links point to the needed distributions, then the index can
   be anything and will be largely ignored.  In the examples, here,
   we'll just point to an empty directory on our link server.  This
   will make our examples run a little bit faster.

path
   A list of additional directories to search for locally-installed
   distributions.

newest
   A boolean value indicating whether to search for new distributions
   when already-installed distributions meet the requirement.  When
   this is true, the default, and when the destination directory is
   not None, then the install function will search for the newest
   distributions that satisfy the requirements.

versions
   A dictionary mapping project names to version numbers to be used
   when selecting distributions.  This can be used to specify a set of
   distribution versions independent of other requirements.


Our link server included a source distribution that includes a simple
extension, extdemo.c::

  #include <Python.h>
  #include <extdemo.h>

  static PyMethodDef methods[] = {};

  PyMODINIT_FUNC
  initextdemo(void)
  {
      PyObject *m;
      m = Py_InitModule3("extdemo", methods, "");
  #ifdef TWO
      PyModule_AddObject(m, "val", PyInt_FromLong(2));
  #else
      PyModule_AddObject(m, "val", PyInt_FromLong(EXTDEMO));
  #endif
  }

The extension depends on a system-dependent include file, extdemo.h,
that defines a constant, EXTDEMO, that is exposed by the extension.

We'll add an include directory to our sample buildout and add the
needed include file to it:

    >>> mkdir('include')
    >>> write('include', 'extdemo.h',
    ... """
    ... #define EXTDEMO 42
    ... """)

Now, we can use the build function to create an egg from the source
distribution:

    >>> zc.buildout.easy_install.build(
    ...   'extdemo', dest,
    ...   {'include-dirs': os.path.join(sample_buildout, 'include')},
    ...   links=[link_server], index=link_server+'index/')
    ['/sample-install/extdemo-1.4-py2.4-unix-i686.egg']

The function returns the list of eggs

Now if we look in our destination directory, we see we have an extdemo egg:

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demo-0.3-py2.4.egg
    d  demoneeded-1.0-py2.4.egg
    d  demoneeded-1.1-py2.4.egg
    d  extdemo-1.4-py2.4-unix-i686.egg

Let's update our link server with a new version of extdemo:

    >>> update_extdemo()
    >>> print_(get(link_server), end='')
    <html><body>
    <a href="bigdemo-0.1-py2.4.egg">bigdemo-0.1-py2.4.egg</a><br>
    <a href="demo-0.1-py2.4.egg">demo-0.1-py2.4.egg</a><br>
    <a href="demo-0.2-py2.4.egg">demo-0.2-py2.4.egg</a><br>
    <a href="demo-0.3-py2.4.egg">demo-0.3-py2.4.egg</a><br>
    <a href="demo-0.4rc1-py2.4.egg">demo-0.4rc1-py2.4.egg</a><br>
    <a href="demoneeded-1.0.zip">demoneeded-1.0.zip</a><br>
    <a href="demoneeded-1.1.zip">demoneeded-1.1.zip</a><br>
    <a href="demoneeded-1.2rc1.zip">demoneeded-1.2rc1.zip</a><br>
    <a href="du_zipped-1.0-pyN.N.egg">du_zipped-1.0-pyN.N.egg</a><br>
    <a href="extdemo-1.4.zip">extdemo-1.4.zip</a><br>
    <a href="extdemo-1.5.zip">extdemo-1.5.zip</a><br>
    <a href="index/">index/</a><br>
    <a href="other-1.0-py2.4.egg">other-1.0-py2.4.egg</a><br>
    </body></html>

The easy_install caches information about servers to reduce network
access. To see the update, we have to call the clear_index_cache
function to clear the index cache:

    >>> zc.buildout.easy_install.clear_index_cache()

If we run build with newest set to False, we won't get an update:

    >>> zc.buildout.easy_install.build(
    ...   'extdemo', dest,
    ...   {'include-dirs': os.path.join(sample_buildout, 'include')},
    ...   links=[link_server], index=link_server+'index/',
    ...   newest=False)
    ['/sample-install/extdemo-1.4-py2.4-linux-i686.egg']

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demo-0.3-py2.4.egg
    d  demoneeded-1.0-py2.4.egg
    d  demoneeded-1.1-py2.4.egg
    d  extdemo-1.4-py2.4-unix-i686.egg

But if we run it with the default True setting for newest, then we'll
get an updated egg:

    >>> zc.buildout.easy_install.build(
    ...   'extdemo', dest,
    ...   {'include-dirs': os.path.join(sample_buildout, 'include')},
    ...   links=[link_server], index=link_server+'index/')
    ['/sample-install/extdemo-1.5-py2.4-unix-i686.egg']

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demo-0.3-py2.4.egg
    d  demoneeded-1.0-py2.4.egg
    d  demoneeded-1.1-py2.4.egg
    d  extdemo-1.4-py2.4-unix-i686.egg
    d  extdemo-1.5-py2.4-unix-i686.egg

The versions option also influences the versions used.  For example,
if we specify a version for extdemo, then that will be used, even
though it isn't the newest.  Let's clean out the destination directory
first:

    >>> import os
    >>> for name in os.listdir(dest):
    ...     remove(dest, name)

    >>> zc.buildout.easy_install.build(
    ...   'extdemo', dest,
    ...   {'include-dirs': os.path.join(sample_buildout, 'include')},
    ...   links=[link_server], index=link_server+'index/',
    ...   versions=dict(extdemo='1.4'))
    ['/sample-install/extdemo-1.4-py2.4-unix-i686.egg']

    >>> ls(dest)
    d  extdemo-1.4-py2.4-unix-i686.egg

Handling custom build options for extensions in develop eggs
------------------------------------------------------------

The develop function is similar to the build function, except that,
rather than building an egg from a source directory containing a
setup.py script.

The develop function takes 2 positional arguments:

setup
   The path to a setup script, typically named "setup.py", or a
   directory containing a setup.py script.

dest
   The directory to install the egg link to

It supports some optional keyword argument:

build_ext
   A dictionary of options to be passed to the distutils build_ext
   command when building extensions.

We have a local directory containing the extdemo source:

    >>> ls(extdemo)
    -  MANIFEST
    -  MANIFEST.in
    -  README
    -  extdemo.c
    -  setup.py

Now, we can use the develop function to create a develop egg from the source
distribution:

    >>> zc.buildout.easy_install.develop(
    ...   extdemo, dest,
    ...   {'include-dirs': os.path.join(sample_buildout, 'include')})
    '/sample-install/extdemo.egg-link'

The name of the egg link created is returned.

Now if we look in our destination directory, we see we have an extdemo
egg link:

    >>> ls(dest)
    d  extdemo-1.4-py2.4-unix-i686.egg
    -  extdemo.egg-link

And that the source directory contains the compiled extension:

    >>> contents = os.listdir(extdemo)
    >>> bool([f for f in contents if f.endswith('.so') or f.endswith('.pyd')])
    True

Download cache
--------------

Normally, when distributions are installed, if any processing is
needed, they are downloaded from the internet to a temporary directory
and then installed from there.  A download cache can be used to avoid
the download step.  This can be useful to reduce network access and to
create source distributions of an entire buildout.

A download cache is specified by calling the download_cache
function.  The function always returns the previous setting. If no
argument is passed, then the setting is unchanged.  If an argument is
passed, the download cache is set to the given path, which must point
to an existing directory.  Passing None clears the cache setting.

To see this work, we'll create a directory and set it as the cache
directory:

    >>> cache = tmpdir('cache')
    >>> zc.buildout.easy_install.download_cache(cache)

We'll recreate our destination directory:

    >>> remove(dest)
    >>> dest = tmpdir('sample-install')

We'd like to see what is being fetched from the server, so we'll
enable server logging:

    >>> _ = get(link_server+'enable_server_logging')
    GET 200 /enable_server_logging

Now, if we install demo, and extdemo:

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo==0.2'], dest,
    ...     links=[link_server], index=link_server+'index/')
    GET 200 /
    GET 404 /index/demo/
    GET 200 /index/
    GET 200 /demo-0.2-py2.4.egg
    GET 404 /index/demoneeded/
    GET 200 /demoneeded-1.1.zip

    >>> zc.buildout.easy_install.build(
    ...   'extdemo', dest,
    ...   {'include-dirs': os.path.join(sample_buildout, 'include')},
    ...   links=[link_server], index=link_server+'index/')
    GET 404 /index/extdemo/
    GET 200 /extdemo-1.5.zip
    ['/sample-install/extdemo-1.5-py2.4-linux-i686.egg']

Not only will we get eggs in our destination directory:

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demoneeded-1.1-py2.4.egg
    d  extdemo-1.5-py2.4-linux-i686.egg

But we'll get distributions in the cache directory:

    >>> ls(cache)
    -  demo-0.2-py2.4.egg
    -  demoneeded-1.1.zip
    -  extdemo-1.5.zip

The cache directory contains uninstalled distributions, such as zipped
eggs or source distributions.

Let's recreate our destination directory and clear the index cache:

    >>> remove(dest)
    >>> dest = tmpdir('sample-install')
    >>> zc.buildout.easy_install.clear_index_cache()

Now when we install the distributions:

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo==0.2'], dest,
    ...     links=[link_server], index=link_server+'index/')
    GET 200 /
    GET 404 /index/demo/
    GET 200 /index/
    GET 404 /index/demoneeded/

    >>> zc.buildout.easy_install.build(
    ...   'extdemo', dest,
    ...   {'include-dirs': os.path.join(sample_buildout, 'include')},
    ...   links=[link_server], index=link_server+'index/')
    GET 404 /index/extdemo/
    ['/sample-install/extdemo-1.5-py2.4-linux-i686.egg']

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demoneeded-1.1-py2.4.egg
    d  extdemo-1.5-py2.4-linux-i686.egg

Note that we didn't download the distributions from the link server.

If we remove the restriction on demo, we'll download a newer version
from the link server:

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest,
    ...     links=[link_server], index=link_server+'index/')
    GET 200 /demo-0.3-py2.4.egg

Normally, the download cache is the preferred source of downloads, but
not the only one.

Installing solely from a download cache
---------------------------------------

A download cache can be used as the basis of application source
releases.  In an application source release, we want to distribute an
application that can be built without making any network accesses.  In
this case, we distribute a download cache and tell the easy_install
module to install from the download cache only, without making network
accesses.  The install_from_cache function can be used to signal that
packages should be installed only from the download cache.  The
function always returns the previous setting.  Calling it with no
arguments returns the current setting without changing it:

    >>> zc.buildout.easy_install.install_from_cache()
    False

Calling it with a boolean value changes the setting and returns the
previous setting:

    >>> zc.buildout.easy_install.install_from_cache(True)
    False

Let's remove demo-0.3-py2.4.egg from the cache, clear the index cache,
recreate the destination directory, and reinstall demo:

    >>> for  f in os.listdir(cache):
    ...     if f.startswith('demo-0.3-'):
    ...         remove(cache, f)

    >>> zc.buildout.easy_install.clear_index_cache()
    >>> remove(dest)
    >>> dest = tmpdir('sample-install')

    >>> ws = zc.buildout.easy_install.install(
    ...     ['demo'], dest,
    ...     links=[link_server], index=link_server+'index/')

    >>> ls(dest)
    d  demo-0.2-py2.4.egg
    d  demoneeded-1.1-py2.4.egg

This time, we didn't download from or even query the link server.

.. Disable the download cache:

    >>> zc.buildout.easy_install.download_cache(None)
    '/cache'

    >>> zc.buildout.easy_install.install_from_cache(False)
    True

Change History
**************

2.4.3 (2015-09-03)
==================

- Added nested directory creation support 
  [guyzmo]


2.4.2 (2015-08-26)
==================

- If a downloaded config file in the "extends-cache" gets corrupted, buildout
  now tells you the filename in the cache. Handy for troubleshooting.
  [reinout]


2.4.1 (2015-08-08)
==================

- Check the ``use-dependency-links`` option earlier.  This can give
  a small speed increase.
  [maurits]

- When using python 2, urllib2 is used to work around Python issue 24599, which
  affects downloading from behind a proxy.
  [stefano-m]


2.4.0 (2015-07-01)
==================

- Buildout no longer breaks on packages that contain a file with a non-ascii
  filename. Fixes #89 and #148.
  [reinout]

- Undo breakage on Windows machines where ``sys.prefix`` can also be a
  ``site-packages`` directory:  don't remove it from ``sys.path``.  See
  https://github.com/buildout/buildout/issues/217 .

- Remove assumption that ``pkg_resources`` is a module (untrue since
  release of `setuptools 8.3``).  See
  https://github.com/buildout/buildout/issues/227 .

- Fix for #212. For certain kinds of conflict errors you'd get an UnpackError
  when rendering the error message. Instead of a nicely formatted version
  conflict message.
  [reinout]

- Making sure we use the correct easy_install when setuptools is installed
  globally. See https://github.com/buildout/buildout/pull/232 and
  https://github.com/buildout/buildout/pull/222 .
  [lrowe]

- Updated buildout's `travis-ci <https://travis-ci.org/buildout/buildout>`_
  configuration so that tests run much quicker so that buildout is easier and
  quicker to develop.
  [reinout]

- Note: zc.recipe.egg has also been updated to 2.0.2 together with this
  zc.buildout release. Fixed: In ``zc.recipe.egg#custom`` recipe's ``rpath``
  support, don't assume path elements are buildout-relative if they start with
  one of the "special" tokens (e.g., ``$ORIGIN``).  See:
  https://github.com/buildout/buildout/issues/225.
  [tseaver]

- ``download-cache``, ``eggs-directory`` and ``extends-cache`` are now
  automatically created if their parent directory exists. Also they can be
  relative directories (relative to the location of the buildout config file
  that defines them). Also they can now be in the form ``~/subdir``, with the
  usual convention that the ``~`` char means the home directory of the user
  running buildout.
  [lelit]

- A new boostrap.py file is released (version 2015-07-01).

- When bootstrapping, the ``develop-eggs/`` directory is first removed. This
  prevents old left-over ``.egg-link`` files from breaking buildout's careful
  package collection mechanism.
  [reinout]

- The bootstrap script now accepts ``--to-dir``. Setuptools is installed
  there. If already available there, it is reused. This can be used to
  bootstrap buildout without internet access. Similarly, a local
  ``ez_setup.py`` is used when available instead of it being downloaded. You
  need setuptools 14.0 or higher for this functionality.
  [lrowe]

- The bootstrap script now uses ``--buildout-version`` instead of
  ``--version`` to pick a specific buildout version.
  [reinout]

- The bootstrap script now accepts ``--version`` which prints the bootstrap
  version. This version is the date the bootstrap.py was last changed. A date
  is handier or less confusing than either tracking zc.buildout's version or
  having a separate bootstrap version number.
  [reinout]

2.3.1 (2014-12-16)
==================

- Fixed: Buildout merged single-version requirements with
  version-range requirements in a way that caused it to think there
  wasn't a single-version requirement.  IOW, buildout throught that
  versions were being picked when they weren't.

- Suppress spurios (and possibly non-spurious) version-parsing warnings.

2.3.0 (2014-12-14)
==================

- Buildout is now compatible with (and requires) setuptools 8.

2.2.5 (2014-11-04)
==================

- Improved fix for #198: when bootstrapping with an extension, buildout was
  too strict on itself, resulting in an inability to upgrade or downgrade its
  own version.
  [reinout]

- Setuptools must be at 3.3 or higher now. If you use the latest bootstrap
  from http://downloads.buildout.org/2/bootstrap.py you're all set.
  [reinout]

- Installing *recipes* that themselves have dependencies used to fail with a
  VersionConflict if such a dependency was installed globally with a lower
  version. Buildout now ignores the version conflict in those cases and simply
  installs the correct version.
  [reinout]

2.2.4 (2014-11-01)
==================

- Fix for #198: buildout 2.2.3 caused a version conflict when bootstrapping a
  buildout with a version pinned to an earlier one. Same version conflict
  could occur with system-wide installed packages that were newer than the
  pinned version.
  [reinout]

2.2.3 (2014-10-30)
==================

- Fix #197, Python 3 regression
  [aclark4life]

2.2.2 (2014-10-30)
==================

- Open files for ``exec()`` in universal newlines mode.  See
  https://github.com/buildout/buildout/issues/130

- Add ``BUILDOUT_HOME`` as an alternate way to control how the user default
  configuration is found.

- Close various files when finished writing to them. This avoids
  ResourceWarnings on Python 3, and better supports doctests under PyPy.

- Introduce improved easy_install Install.install function. This is present
  in 1.5.X and 1.7X but was never merged into 2.X somehow.

2.2.1 (2013-09-05)
==================

- ``distutils`` scripts: correct order of operations on ``from ... import``
  lines (see https://github.com/buildout/buildout/issues/134).

- Add an ``--allow-site-packges`` option to ``bootstrap.py``, defaulting
  to False.  If the value is false, strip any "site packages" (as defined by
  the ``site`` module) from ``sys.path`` before attempting to import
  ``setuptools`` / ``pkg_resources``.

- Updated the URL used to fetch ``ez_setup.py`` to the official, non-version-
  pinned version.

2.2.0 (2013-07-05)
==================

- Handle both addition and subtraction of elements (+= and -=) on the same key
  in the same section. Forward-ported from buildout 1.6.

- Suppress the useless ``Link to <URL> ***BLOCKED*** by --allow-hosts``
  error message being emitted by distribute / setuptools.

- Extend distutils script generation to support module docstrings and
  __future__ imports.

- Refactored picked versions logic to make it easier to use for plugins.

- Use ``get_win_launcher`` API to find Windows launcher (falling back to
  ``resource_string`` for ``cli.exe``).

- Remove ``data_files`` from ``setup.py``:  it was installing ``README.txt``
  in current directory during installation (merged from 1.x branch).

- Switch dependency from ``distribute 0.6.x`` to ``setuptools 0.7.x``.

2.1.0 (2013-03-23)
==================

- `Meta-recipe support`_

- `Conditional sections`_

- Buildout now accepts a ``--version`` command-line option to print
  its version.

Fixed: Builout didn't exit with a non-zero exit status if there was a
       failure in combination with an upgrade.

Fixed: We now fail with an informative error when an old bootstrap
       script causes buildout 2 to be used with setuptools.

Fixed: An error incorrectly suggested that buildout 2 implemented all
       of the functionality of dumppickedversions.

Fixed: Buildout generated bad scripts when no eggs needed to be added
       to ``sys.path``.

Fixed: Buildout didn't honour Unix umask when generating scripts.
       https://bugs.launchpad.net/zc.buildout/+bug/180705

Fixed: ``update-versions-file`` didn't work unless
       ``show-picked-versions`` was also set.
       https://github.com/buildout/buildout/issues/71

2.0.1 (2013-02-16)
==================

- Fixed: buildout didn't honor umask settings when creating scripts.

- Fix for distutils scripts installation on Python 3, related to
  ``__pycache__`` directories.

- Fixed: encoding data in non-entry-point-based scripts was lost.


2.0.0 (2013-02-10)
==================

This is a backward incompatible release of buildout that attempts to
correct mistakes made in buildout 1.

- Buildout no-longer tries to provide full or partial isolation from
  system Python installations. If you want isolation, use buildout
  with virtualenv, or use a clean build of Python to begin with.

  Providing isolation was a noble goal, but it's implementation
  complicated buildout's implementation too much.

- Buildout no-longer supports using multiple versions of Python in a
  single buildout.  This too was a noble goal, but added too much
  complexity to the implementation.

- Changed the configuration file format:

  - Relative indentation in option values is retained if the first
    line is blank. (IOW, if the non-blank text is on the continuation
    lines.) As in::

       [mysection]
       tree =
         /root
           branch

    In such cases, internal blank lines are also retained.

  - The configuration syntax is more tightly defined, allowing fewer
    syntax definitions.

    Buildout 1 configuration files were parsed with the Python
    ConfigParser module. The ConfigParser module's format is poorly
    documented and wildly flexible. For example:

    - Any characters other than left square brackets were allowed in
      section names.

    - Arbitrary text was allowed and ignored after the closing bracket on
      section header lines.

    - Any characters other than equal signs or colons were allowed in an
      option name.

    - Configuration options could be spelled as RFC 822 mail headers
      (using a colon, rather than an equal sign).

    - Comments could begin with "rem".

    - Semicolons could be used to start inline comments, but only if
      preceded by a whitespace character.

  See `Configuration file syntax`_.

- Buildout now prefers final releases by default
  (buildout:prefer-final now defaults to true, rather than false.)

  However, if buildout is bootstrapped with a non-final release, it
  won't downgrade itself to a final release.

- Buildout no-longer installs zipped eggs. (Distribute may still
  install a zipped egg of itself during the bootstrapping process.)
  The ``buildout:unzip`` option has been removed.

- Buildout no-longer supports setuptools. It now uses distribute
  exclusively.

- Integrated the `buildout-versions
  <http://packages.python.org/buildout-versions/>`_ extension into buildout
  itself. For this, a few options were added to buildout:

  - If ``show-picked-versions`` is set to true, all picked versions are
    printed at the end of the buildout run. This saves you from running
    buildout in verbose mode and extracting the picked versions from the
    output.

  - If ``update-versions-file`` is set to a filename (relative to the buildout
    directory), the ``show-picked-versions`` output is appended to that file.

- Buildout options can be given on the command line using the form::

    option_name=value

  as a short-hand for::

    buildout:option_name=value

- The ``versions`` option now defaults to ``versions``, so you no
  longer need to include::

     versions = versions

  in a ``buildout`` section when pinning versions.

  A ``versions`` section is added, if necessary, if a ``versions``
  option isn't used.

- Buildout-defined default versions are included in the versions
  section, if there is one.

- The ``buildout:zc.buildout-version`` and
  ``buildout:distribute-version`` options have been removed in favor
  of providing version constraints in a versions section.

- Error if install-from-cache and offline are used together, because
  offline largely means "don't install".

- Provide better error messages when distributions can't be installed
  because buildout is run in offline mode.

- Versions in versions sections can now be simple constraints, like
  >=2.0dev in addition to being simple versions.

  Buildout 2 leverages this to make sure it uses
  zc.recipe.egg>=2.0.0a3, which mainly matters for Python 3.

- The buildout init command now accepts distribution requirements and
  paths to set up a custom interpreter part that has the distributions
  or parts in the path. For example::

     python bootstrap.py init BeautifulSoup

- Added buildout:socket-timeout option so that socket timeout can be configured
  both from command line and from config files. (gotcha)

- Distutils-style scripts are also installed now (for instance pyflakes' and
  docutils' scripts).  https://bugs.launchpad.net/zc.buildout/+bug/422724

- Avoid sorting the working set and requirements when it won't be
  logged.  When profiling a simple buildout with 10 parts with
  identical and large working sets, this resulted in a decrease of run
  time from 93.411 to 15.068 seconds, about a 6 fold improvement.  To
  see the benefit be sure to run without any increase in verbosity
  ("-v" option).  (rossp)

- Introduce a cache for the expensive `buildout._dir_hash` function.

- Remove duplicate path from script's sys.path setup.

- Make sure to download extended configuration files only once per buildout
  run even if they are referenced multiple times (patch by Rafael Monnerat).

- Removed any traces of the implementation of ``extended-by``. Raise a
  UserError if the option is encountered instead of ignoring it, though.

Fixed: relative-paths weren't honored when bootstrapping or upgrading
       (which is how the buildout script gets generated).

Fixed: initialization code wasn't included in interpreter scripts.

Fixed: macro inheritance bug, https://github.com/buildout/buildout/pull/37

Fixed: In the download module, fixed the handling of directories that
       are pointed to by file-system paths and ``file:`` URLs.

Fixed if you have a configuration with an extends entry in the [buildout]
      section which points to a non-existing URL the result is not very
      user friendly. https://bugs.launchpad.net/zc.buildout/+bug/566167

Fixed: https://bugs.launchpad.net/bugs/697913 : Buildout doesn't honor exit code
       from scripts. Fixed.

1.4.4 (2010-08-20)
==================

The 1.4.4 release is a release for people who encounter trouble
with the 1.5 line.  By switching to `the associated bootstrap script
<https://raw.github.com/buildout/buildout/master/bootstrap/bootstrap.py>`_
you can stay on 1.4.4 until you are ready to migrate.

1.4.3 (2009-12-10)
==================

Bugs fixed:

- Using pre-detected setuptools version for easy_installing tgz files.  This
  prevents a recursion error when easy_installing an upgraded "distribute"
  tgz.  Note that setuptools did not have this recursion problem solely
  because it was packaged as an ``.egg``, which does not have to go through
  the easy_install step.


1.4.2 (2009-11-01)
==================

New Feature:

- Added a --distribute option to the bootstrap script, in order
  to use Distribute rather than Setuptools. By default, Setuptools
  is used.

Bugs fixed:

- While checking for new versions of setuptools and buildout itself,
  compare requirement locations instead of requirement objects.

- Incrementing didn't work properly when extending multiple files.
  https://bugs.launchpad.net/zc.buildout/+bug/421022

- The download API computed MD5 checksums of text files wrong on Windows.

1.4.1 (2009-08-27)
==================

New Feature:

- Added a debug built-in recipe to make writing some tests easier.

Bugs fixed:

- (introduced in 1.4.0) option incrementing (-=) and decrementing (-=)
  didn't work in the buildout section.
  https://bugs.launchpad.net/zc.buildout/+bug/420463

- Option incrementing and decrementing didn't work for options
  specified on the command line.

- Scripts generated with relative-paths enabled couldn't be
  symbolically linked to other locations and still work.

- Scripts run using generated interpreters didn't have __file__ set correctly.

- The standard Python -m option didn't work for custom interpreters.

1.4.0 (2009-08-26)
==================

- When doing variable substitutions, you can omit the section name to
  refer to a variable in the same section (e.g. ${:foo}).

- When doing variable substitution, you can use the special option,
  ``_buildout_section_name_`` to get the section name.  This is most handy
  for getting the current section name (e.g. ${:_buildout_section_name_}).

- A new special option, ``<`` allows sections to be used as macros.

- Added annotate command for annotated sections. Displays sections
  key-value pairs along with the value origin.

- Added a download API that handles the download cache, offline mode etc and
  is meant to be reused by recipes.

- Used the download API to allow caching of base configurations (specified by
  the buildout section's 'extends' option).

1.3.1 (2009-08-12)
==================

- Bug fixed: extras were ignored in some cases when versions were specified.

1.3.0 (2009-06-22)
==================

- Better Windows compatibility in test infrastructure.

- Now the bootstrap.py has an optional --version argument,
  that can be used to force buildout version to use.

- ``zc.buildout.testing.buildoutSetUp`` installs a new handler in the
  python root logging facility. This handler is now removed during
  tear down as it might disturb other packages reusing buildout's
  testing infrastructure.

- fixed usage of 'relative_paths' keyword parameter on Windows

- Added an unload entry point for extensions.

- Fixed bug: when the relative paths option was used, relative paths
  could be inserted into sys.path if a relative path was used to run
  the generated script.

1.2.1 (2009-03-18)
==================

- Refactored generation of relative egg paths to generate simpler code.

1.2.0 (2009-03-17)
==================

- Added a relative_paths option to zc.buildout.easy_install.script to
  generate egg paths relative to the script they're used in.

1.1.2 (2009-03-16)
==================

- Added Python 2.6 support. Removed Python 2.3 support.

- Fixed remaining deprecation warnings under Python 2.6, both when running
  our tests and when using the package.

- Switched from using os.popen* to subprocess.Popen, to avoid a deprecation
  warning in Python 2.6.  See:

  http://docs.python.org/library/subprocess.html#replacing-os-popen-os-popen2-os-popen3

- Made sure the 'redo_pyc' function and the doctest checkers work with Python
  executable paths containing spaces.

- Expand shell patterns when processing the list of paths in `develop`, e.g::

    [buildout]
    develop = ./local-checkouts/*

- Conditionally import and use hashlib.md5 when it's available instead
  of md5 module, which is deprecated in Python 2.6.

- Added Jython support for bootstrap, development bootstrap
  and buildout support on Jython

- Fixed a bug that would cause buildout to break while computing a
  directory hash if it found a broken symlink (Launchpad #250573)

1.1.1 (2008-07-28)
==================

- Fixed a bug that caused buildouts to fail when variable
  substitutions are used to name standard directories, as in::

    [buildout]
    eggs-directory = ${buildout:directory}/develop-eggs

1.1.0 (2008-07-19)
==================

- Added a buildout-level unzip option to change the default policy for
  unzipping zip-safe eggs.

- Tracebacks are now printed for internal errors (as opposed to user
  errors) even without the -D option.

- pyc and pyo files are regenerated for installed eggs so that the
  stored path in code objects matches the install location.

1.0.6 (2008-06-13)
==================

- Manually reverted the changeset for the fix for
  https://bugs.launchpad.net/zc.buildout/+bug/239212 to verify thet the test
  actually fails with the changeset:
  http://svn.zope.org/zc.buildout/trunk/src/zc/buildout/buildout.py?rev=87309&r1=87277&r2=87309
  Thanks tarek for pointing this out. (seletz)

- fixed the test for the += -= syntax in buildout.txt as the test
  was actually wrong. The original implementation did a split/join
  on whitespace, and later on that was corrected to respect the original
  EOL setting, the test was not updated, though. (seletz)

- added a test to verify against https://bugs.launchpad.net/zc.buildout/+bug/239212
  in allowhosts.txt (seletz)

- further fixes for """AttributeError: Buildout instance has no
  attribute '_logger'""" by providing reasonable defaults
  within the Buildout constructor (related to the new 'allow-hosts' option)
  (patch by Gottfried Ganssauge) (ajung)


1.0.5 (2008-06-10)
==================

- Fixed wrong split when using the += and -= syntax (mustapha)

1.0.4 (2008-06-10)
==================

- Added the `allow-hosts` option (tarek)

- Quote the 'executable' argument when trying to detect the python
  version using popen4. (sidnei)

- Quote the 'spec' argument, as in the case of installing an egg from
  the buildout-cache, if the filename contains spaces it would fail (sidnei)

- Extended configuration syntax to allow -= and += operators (malthe, mustapha).

1.0.3 (2008-06-01)
==================

- fix for """AttributeError: Buildout instance has no attribute '_logger'"""
  by providing reasonable defaults within the Buildout constructor.
  (patch by Gottfried Ganssauge) (ajung)

1.0.2 (2008-05-13)
==================

- More fixes for Windows. A quoted sh-bang is now used on Windows to make the
  .exe files work with a Python executable in 'program files'.

- Added "-t <timeout_in_seconds>" option for specifying the socket timeout.
  (ajung)

1.0.1 (2008-04-02)
==================

- Made easy_install.py's _get_version accept non-final releases of Python,
  like 2.4.4c0. (hannosch)

- Applied various patches for Windows (patch by Gottfried Ganssauge). (ajung)

- Applied patch fixing rmtree issues on Windows (patch by
  Gottfried Ganssauge).  (ajung)

1.0.0 (2008-01-13)
==================

- Added a French translation of the buildout tutorial.

1.0.0b31 (2007-11-01)
=====================

Feature Changes
---------------

- Added a configuration option that allows buildouts to ignore
  dependency_links metadata specified in setup. By default
  dependency_links in setup are used in addition to buildout specified
  find-links. This can make it hard to control where eggs come
  from. Here's how to tell buildout to ignore URLs in
  dependency_links::

    [buildout]
    use-dependency-links = false

  By default use-dependency-links is true, which matches the behavior
  of previous versions of buildout.

- Added a configuration option that causes buildout to error if a
  version is picked. This is a nice safety belt when fixing all
  versions is intended, especially when creating releases.

Bugs Fixed
----------

- 151820: Develop failed if the setup.py script imported modules in
  the distribution directory.

- Verbose logging of the develop command was omitting detailed
  output.

- The setup command wasn't documented.

- The setup command failed if run in a directory without specifying a
  configuration file.

- The setup command raised a stupid exception if run without arguments.

- When using a local find links or index, distributions weren't copied
  to the download cache.

- When installing from source releases, a version specification (via a
  buildout versions section) for setuptools was ignored when deciding
  which setuptools to use to build an egg from the source release.

1.0.0b30 (2007-08-20)
=====================

Feature Changes
---------------

- Changed the default policy back to what it was to avoid breakage in
  existing buildouts.  Use::

    [buildout]
    prefer-final = true

  to get the new policy.  The new policy will go into effect in
  buildout 2.

1.0.0b29 (2007-08-20)
=====================

Feature Changes
---------------

- Now, final distributions are preferred over non-final versions.  If
  both final and non-final versions satisfy a requirement, then the
  final version will be used even if it is older.  The normal way to
  override this for specific packages is to specifically require a
  non-final version, either specifically or via a lower bound.

- There is a buildout prefer-final version that can be used with a
  value of "false"::

    prefer-final = false

  To prefer newer versions, regardless of whether or not they are
  final, buildout-wide.

- The new simple Python index, http://cheeseshop.python.org/simple, is
  used as the default index.  This will provide better performance
  than the human package index interface,
  http://pypi.python.org/pypi. More importantly, it lists hidden
  distributions, so buildouts with fixed distribution versions will be
  able to find old distributions even if the distributions have been
  hidden in the human PyPI interface.

Bugs Fixed
----------

- 126441: Look for default.cfg in the right place on Windows.

1.0.0b28 (2007-07-05)
=====================

Bugs Fixed
----------

- When requiring a specific version, buildout looked for new versions
  even if that single version was already installed.

1.0.0b27 (2007-06-20)
=====================

Bugs Fixed
----------

- Scripts were generated incorrectly on Windows.  This included the
  buildout script itself, making buildout completely unusable.

1.0.0b26 (2007-06-19)
=====================

Feature Changes
---------------

- Thanks to recent fixes in setuptools, I was able to change buildout
  to use find-link and index information when searching extensions.

  Sadly, this work, especially the timing, was motivated my the need
  to use alternate indexes due to performance problems in the cheese
  shop (http://www.python.org/pypi/).  I really home we can address
  these performance problems soon.

1.0.0b25 (2007-05-31)
=====================

Feature Changes
---------------

- buildout now changes to the buildout directory before running recipe
  install and update methods.

- Added a new init command for creating a new buildout. This creates
  an empty configuration file and then bootstraps.

- Except when using the new init command, it is now an error to run
  buildout without a configuration file.

- In verbose mode, when adding distributions to fulfil requirements of
  already-added distributions, we now show why the new distributions
  are being added.

- Changed the logging format to exclude the logger name for the
  buildout logger.  This reduces noise in the output.

- Clean up lots of messages, adding missing periods and adding quotes around
  requirement strings and file paths.

Bugs Fixed
----------

- 114614: Buildouts could take a very long time if there were
  dependency problems in large sets of pathologically interdependent
  packages.

- 59270: Buggy recipes can cause failures in later recipes via chdir

- 61890: file:// urls don't seem to work in find-links

  setuptools requires that file urls that point to directories must
  end in a "/".  Added a workaround.

- 75607: buildout should not run if it creates an empty buildout.cfg

1.0.0b24 (2007-05-09)
=====================

Feature Changes
---------------

- Improved error reporting by showing which packages require other
  packages that can't be found or that cause version conflicts.

- Added an API for use by recipe writers to clean up created files
  when recipe errors occur.

- Log installed scripts.

Bugs Fixed
----------

- 92891: bootstrap crashes with recipe option in buildout section.

- 113085: Buildout exited with a zero exist status when internal errors
  occurred.


1.0.0b23 (2007-03-19)
=====================

Feature Changes
---------------

- Added support for download caches.  A buildout can specify a cache
  for distribution downloads.  The cache can be shared among buildouts
  to reduce network access and to support creating source
  distributions for applications allowing install without network
  access.

- Log scripts created, as suggested in:
  https://bugs.launchpad.net/zc.buildout/+bug/71353

Bugs Fixed
----------

- It wasn't possible to give options on the command line for sections
  not defined in a configuration file.

1.0.0b22 (2007-03-15)
=====================

Feature Changes
---------------

- Improved error reporting and debugging support:

  - Added "logical tracebacks" that show functionally what the buildout
    was doing when an error occurs.  Don't show a Python traceback
    unless the -D option is used.

  - Added a -D option that causes the buildout to print a traceback and
    start the pdb post-mortem debugger when an error occurs.

  - Warnings are printed for unused options in the buildout section and
    installed-part sections.  This should make it easier to catch option
    misspellings.

- Changed the way the installed database (.installed.cfg) is handled
  to avoid database corruption when a user breaks out of a buildout
  with control-c.

- Don't save an installed database if there are no installed parts or
  develop egg links.

1.0.0b21 (2007-03-06)
=====================

Feature Changes
---------------

- Added support for repeatable buildouts by allowing egg versions to
  be specified in a versions section.

- The easy_install module install and build functions now accept a
  versions argument that supplied to mapping from project name to
  version numbers.  This can be used to fix version numbers for
  required distributions and their dependencies.

  When a version isn't fixed, using either a versions option or using
  a fixed version number in a requirement, then a debug log message is
  emitted indicating the version picked.  This is useful for setting
  versions options.

  A default_versions function can be used to set a default value for
  this option.

- Adjusted the output for verbosity levels.  Using a single -v option
  no longer causes voluminous setuptools output.  Using -vv and -vvv
  now triggers extra setuptools output.

- Added a remove testing helper function that removes files or directories.

1.0.0b20 (2007-02-08)
=====================

Feature Changes
---------------

- Added a buildout newest option, to control whether the newest
  distributions should be sought to meet requirements.  This might
  also provide a hint to recipes that don't deal with
  distributions. For example, a recipe that manages subversion
  checkouts might not update a checkout if newest is set to "false".

- Added a *newest* keyword parameter to the
  zc.buildout.easy_install.install and zc.buildout.easy_install.build
  functions to control whether the newest distributions that need
  given requirements should be sought.  If a false value is provided
  for this parameter and already installed eggs meet the given
  requirements, then no attempt will be made to search for newer
  distributions.

- The recipe-testing support setUp function now adds the name
  *buildout* to the test namespace with a value that is the path to
  the buildout script in the sample buildout.  This allows tests to
  use

    >>> print system(buildout),

  rather than:

    >>> print system(join('bin', 'buildout')),


Bugs Fixed
----------

- Paths returned from update methods replaced lists of installed files
  rather than augmenting them.

1.0.0b19 (2007-01-24)
=====================

Bugs Fixed
----------

- Explicitly specifying a Python executable failed if the output of
  running Python with the -V option included a 2-digit (rather than a
  3-digit) version number.

1.0.0b18 (2007-01-22)
=====================

Feature Changes
---------------

- Added documentation for some previously undocumented features of the
  easy_install APIs.

- By popular demand, added a -o command-line option that is a short
  hand for the assignment buildout:offline=true.

Bugs Fixed
----------

- When deciding whether recipe develop eggs had changed, buildout
  incorrectly considered files in .svn and CVS directories.

1.0.0b17 (2006-12-07)
=====================

Feature Changes
---------------

- Configuration files can now be loaded from URLs.

Bugs Fixed
----------

- https://bugs.launchpad.net/products/zc.buildout/+bug/71246

  Buildout extensions installed as eggs couldn't be loaded in offline
  mode.


1.0.0b16 (2006-12-07)
=====================

Feature Changes
---------------

- A new command-line argument, -U, suppresses reading user defaults.

- You can now suppress use of an installed-part database
  (e.g. .installed.cfg) by specifying an empty value for the buildout
  installed option.

Bugs Fixed
----------

- When the install command is used with a list of parts, only
  those parts are supposed to be installed, but the buildout was also
  building parts that those parts depended on.

1.0.0b15 (2006-12-06)
=====================

Bugs Fixed
----------

- Uninstall recipes weren't loaded correctly in cases where
  no parts in the (new) configuration used the recipe egg.

1.0.0b14 (2006-12-05)
=====================

Feature Changes
---------------

- Added uninstall recipes for dealing with complex uninstallation
  scenarios.

Bugs Fixed
----------

- Automatic upgrades weren't performed on Windows due to a bug that
  caused buildout to incorrectly determine that it wasn't running
  locally in a buildout.

- Fixed some spurious test failures on Windows.

1.0.0b13 (2006-12-04)
=====================

Feature Changes
---------------

- Variable substitutions now reflect option data written by recipes.

- A part referenced by a part in a parts list is now added to the parts
  list before the referencing part.  This means that you can omit
  parts from the parts list if they are referenced by other parts.

- Added a develop function to the easy_install module to aid in
  creating develop eggs with custom build_ext options.

- The build and develop functions in the easy_install module now
  return the path of the egg or egg link created.

- Removed the limitation that parts named in the install command can
  only name configured parts.

- Removed support ConfigParser-style variable substitutions
  (e.g. %(foo)s). Only the string-template style of variable
  (e.g. ${section:option}) substitutions will be supported.
  Supporting both violates "there's only one way to do it".

- Deprecated the buildout-section extendedBy option.

Bugs Fixed
----------

- We treat setuptools as a dependency of any distribution that
  (declares that it) uses namespace packages, whether it declares
  setuptools as a dependency or not.  This wasn't working for eggs
  installed by virtue of being dependencies.


1.0.0b12 (2006-10-24)
=====================

Feature Changes
---------------

- Added an initialization argument to the
  zc.buildout.easy_install.scripts function to include initialization
  code in generated scripts.

1.0.0b11 (2006-10-24)
=====================

Bugs Fixed
----------

`67737 <https://launchpad.net/products/zc.buildout/+bug/67737>`_
     Verbose and quite output options caused errors when the
     develop buildout option was used to create develop eggs.

`67871 <https://launchpad.net/products/zc.buildout/+bug/67871>`_
     Installation failed if the source was a (local) unzipped
     egg.

`67873 <https://launchpad.net/products/zc.buildout/+bug/67873>`_
     There was an error in producing an error message when part names
     passed to the install command weren't included in the
     configuration.

1.0.0b10 (2006-10-16)
=====================

Feature Changes
---------------

- Renamed the runsetup command to setup. (The old name still works.)

- Added a recipe update method. Now install is only called when a part
  is installed for the first time, or after an uninstall. Otherwise,
  update is called.  For backward compatibility, recipes that don't
  define update methods are still supported.

- If a distribution defines namespace packages but fails to declare
  setuptools as one of its dependencies, we now treat setuptools as an
  implicit dependency.  We generate a warning if the distribution
  is a develop egg.

- You can now create develop eggs for setup scripts that don't use setuptools.

Bugs Fixed
----------

- Egg links weren't removed when corresponding entries were removed
  from develop sections.

- Running a non-local buildout command (one not installed in the
  buildout) led to a hang if there were new versions of buildout or
  setuptools were available.  Now we issue a warning and don't
  upgrade.

- When installing zip-safe eggs from local directories, the eggs were
  moved, rather than copied, removing them from the source directory.

1.0.0b9 (2006-10-02)
====================

Bugs Fixed
----------

Non-zip-safe eggs were not unzipped when they were installed.

1.0.0b8 (2006-10-01)
====================

Bugs Fixed
----------

- Installing source distributions failed when using alternate Python
  versions (depending on the versions of Python used.)

- Installing eggs wasn't handled as efficiently as possible due to a
  bug in egg URL parsing.

- Fixed a bug in runsetup that caused setup scripts that introspected
  __file__ to fail.

1.0.0b7
=======

Added a documented testing framework for use by recipes. Refactored
the buildout tests to use it.

Added a runsetup command run a setup script.  This is handy if, like
me, you don't install setuptools in your system Python.

1.0.0b6
=======

Fixed https://launchpad.net/products/zc.buildout/+bug/60582
Use of extension options caused bootstrapping to fail if the eggs
directory didn't already exist.  We no longer use extensions for
bootstrapping.  There really isn't any reason to anyway.


1.0.0b5
=======

Refactored to do more work in buildout and less work in easy_install.
This makes things go a little faster, makes errors a little easier to
handle, and allows extensions (like the sftp extension) to influence
more of the process. This was done to fix a problem in using the sftp
support.

1.0.0b4
=======

- Added an **experimental** extensions mechanism, mainly to support
  adding sftp support to buildouts that need it.

- Fixed buildout self-updating on Windows.

1.0.0b3
=======

- Added a help option (-h, --help)

- Increased the default level of verbosity.

- Buildouts now automatically update themselves to new versions of
  buildout and setuptools.

- Added Windows support.

- Added a recipe API for generating user errors.

- No-longer generate a py_zc.buildout script.

- Fixed some bugs in variable substitutions.

  The characters "-", "." and " ", weren't allowed in section or
  option names.

  Substitutions with invalid names were ignored, which caused
  misleading failures downstream.

- Improved error handling.  No longer show tracebacks for user errors.

- Now require a recipe option (and therefore a section) for every part.

- Expanded the easy_install module API to:

  - Allow extra paths to be provided

  - Specify explicit entry points

  - Specify entry-point arguments

1.0.0b2
=======

Added support for specifying some build_ext options when installing eggs
from source distributions.

1.0.0b1
=======

- Changed the bootstrapping code to only install setuptools and
  buildout. The bootstrap code no-longer runs the buildout itself.
  This was to fix a bug that caused parts to be recreated
  unnecessarily because the recipe signature in the initial buildout
  reflected temporary locations for setuptools and buildout.

- Now create a minimal setup.py if it doesn't exist and issue a
  warning that it is being created.

- Fixed bug in saving installed configuration data.  %'s and extra
  spaces weren't quoted.

1.0.0a1
=======

Initial public version


