Add documentation for the packaging module.

This updates the user guide to refer to Packaging instead of Distutils.
Some files still require an update.

1 files changed, 324 insertions, 0 deletions

diff --git a/Doc/library/packaging.database.rst b/Doc/library/packaging.database.rst
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+:mod:`packaging.database` --- Database of installed distributions
+=================================================================
+
+.. module:: packaging.database
+   :synopsis: Functions to query and manipulate installed distributions.
+
+
+This module provides an implementation of :PEP:`376`.  It was originally
+intended to land in :mod:`pkgutil`, but with the inclusion of Packaging in the
+standard library, it was thought best to include it in a submodule of
+:mod:`packaging`, leaving :mod:`pkgutil` to deal with imports.
+
+Installed Python distributions are represented by instances of
+:class:`Distribution`, or :class:`EggInfoDistribution` for legacy egg formats.
+Most functions also provide an extra argument ``use_egg_info`` to take legacy
+distributions into account.
+
+
+Classes representing installed distributions
+--------------------------------------------
+
+.. class:: Distribution(path)
+
+   Class representing an installed distribution.  It is different from
+   :class:`packaging.dist.Distribution` which holds the list of files, the
+   metadata and options during the run of a Packaging command.
+
+   Instantiate with the *path* to a ``.dist-info`` directory.  Instances can be
+   compared and sorted.  Other available methods are:
+
+   .. XXX describe how comparison works
+
+   .. method:: get_distinfo_file(path, binary=False)
+
+      Return a read-only file object for a file located at
+      :file:`{project-version}.dist-info/path}`.  *path* should be a
+      ``'/'``-separated path relative to the ``.dist-info`` directory or an
+      absolute path; if it is an absolute path and doesn't start with the path
+      to the :file:`.dist-info` directory, a :class:`PackagingError` is raised.
+
+      If *binary* is ``True``, the file is opened in binary mode.
+
+   .. method:: get_resource_path(relative_path)
+
+      .. TODO
+
+   .. method:: list_distinfo_files(local=False)
+
+      Return an iterator over all files located in the :file:`.dist-info`
+      directory.  If *local* is ``True``, each returned path is transformed into
+      a local absolute path, otherwise the raw value found in the :file:`RECORD`
+      file is returned.
+
+   .. method::  list_installed_files(local=False)
+
+      Iterate over the files installed with the distribution and registered in
+      the :file:`RECORD` file and yield a tuple ``(path, md5, size)`` for each
+      line.  If *local* is ``True``, the returned path is transformed into a
+      local absolute path, otherwise the raw value is returned.
+
+      A local absolute path is an absolute path in which occurrences of ``'/'``
+      have been replaced by :data:`os.sep`.
+
+   .. method:: uses(path)
+
+      Check whether *path* was installed by this distribution (i.e. if the path
+      is present in the :file:`RECORD` file).  *path* can be a local absolute
+      path or a relative ``'/'``-separated path.  Returns a boolean.
+
+   Available attributes:
+
+   .. attribute:: metadata
+
+      Instance of :class:`packaging.metadata.Metadata` filled with the contents
+      of the :file:`{project-version}.dist-info/METADATA` file.
+
+   .. attribute:: name
+
+      Shortcut for ``metadata['Name']``.
+
+   .. attribute:: version
+
+      Shortcut for ``metadata['Version']``.
+
+   .. attribute:: requested
+
+      Boolean indicating whether this distribution was requested by the user of
+      automatically installed as a dependency.
+
+
+.. class:: EggInfoDistribution(path)
+
+   Class representing a legacy distribution.  It is compatible with distutils'
+   and setuptools' :file:`.egg-info` and :file:`.egg` files and directories.
+
+   .. FIXME should be named EggDistribution
+
+   Instantiate with the *path* to an egg file or directory.  Instances can be
+   compared and sorted.  Other available methods are:
+
+   .. method:: list_installed_files(local=False)
+
+   .. method:: uses(path)
+
+   Available attributes:
+
+   .. attribute:: metadata
+
+      Instance of :class:`packaging.metadata.Metadata` filled with the contents
+      of the :file:`{project-version}.egg-info/PKG-INFO` or
+      :file:`{project-version}.egg` file.
+
+   .. attribute:: name
+
+      Shortcut for ``metadata['Name']``.
+
+   .. attribute:: version
+
+      Shortcut for ``metadata['Version']``.
+
+
+Functions to work with the database
+-----------------------------------
+
+.. function:: get_distribution(name, use_egg_info=False, paths=None)
+
+   Return an instance of :class:`Distribution` or :class:`EggInfoDistribution`
+   for the first installed distribution matching *name*.  Egg distributions are
+   considered only if *use_egg_info* is true; if both a dist-info and an egg
+   file are found, the dist-info prevails.  The directories to be searched are
+   given in *paths*, which defaults to :data:`sys.path`.  Return ``None`` if no
+   matching distribution is found.
+
+   .. FIXME param should be named use_egg
+
+
+.. function:: get_distributions(use_egg_info=False, paths=None)
+
+   Return an iterator of :class:`Distribution` instances for all installed
+   distributions found in *paths* (defaults to :data:`sys.path`).  If
+   *use_egg_info* is true, also return instances of :class:`EggInfoDistribution`
+   for legacy distributions found.
+
+
+.. function:: get_file_users(path)
+
+   Return an iterator over all distributions using *path*, a local absolute path
+   or a relative ``'/'``-separated path.
+
+   .. XXX does this work with prefixes or full file path only?
+
+
+.. function:: obsoletes_distribution(name, version=None, use_egg_info=False)
+
+   Return an iterator over all distributions that declare they obsolete *name*.
+   *version* is an optional argument to match only specific releases (see
+   :mod:`packaging.version`).  If *use_egg_info* is true, legacy egg
+   distributions will be considered as well.
+
+
+.. function:: provides_distribution(name, version=None, use_egg_info=False)
+
+   Return an iterator over all distributions that declare they provide *name*.
+   *version* is an optional argument to match only specific releases (see
+   :mod:`packaging.version`).  If *use_egg_info* is true, legacy egg
+   distributions will be considered as well.
+
+
+Utility functions
+-----------------
+
+.. function:: distinfo_dirname(name, version)
+
+   Escape *name* and *version* into a filename-safe form and return the
+   directory name built from them, for example
+   :file:`{safename}-{safeversion}.dist-info.`  In *name*, runs of
+   non-alphanumeric characters are replaced with one ``'_'``; in *version*,
+   spaces become dots, and runs of other non-alphanumeric characters (except
+   dots) a replaced by one ``'-'``.
+
+   .. XXX wth spaces in version numbers?
+
+For performance purposes, the list of distributions is being internally
+cached.   Caching is enabled by default, but you can control it with these
+functions:
+
+.. function:: clear_cache()
+
+   Clear the cache.
+
+.. function:: disable_cache()
+
+   Disable the cache, without clearing it.
+
+.. function:: enable_cache()
+
+   Enable the internal cache, without clearing it.
+
+
+Examples
+--------
+
+Print all information about a distribution
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Given a path to a ``.dist-info`` distribution, we shall print out all
+information that can be obtained using functions provided in this module::
+
+   import sys
+   import packaging.database
+
+   path = input()
+   # first create the Distribution instance
+   try:
+       dist = packaging.database.Distribution(path)
+   except IOError:
+       sys.exit('No such distribution')
+
+   print('Information about %r' % dist.name)
+   print()
+
+   print('Files')
+   print('=====')
+   for path, md5, size in dist.list_installed_files():
+       print('* Path: %s' % path)
+       print('  Hash %s, Size: %s bytes' % (md5, size))
+   print()
+
+   print('Metadata')
+   print('========')
+   for key, value in dist.metadata.items():
+       print('%20s: %s' % (key, value))
+   print()
+
+   print('Extra')
+   print('=====')
+   if dist.requested:
+       print('* It was installed by user request')
+   else:
+       print('* It was installed as a dependency')
+
+If we save the script above as ``print_info.py``, we can use it to extract
+information from a :file:`.dist-info` directory.  By typing in the console:
+
+.. code-block:: sh
+
+   $ echo /tmp/choxie/choxie-2.0.0.9.dist-info | python3 print_info.py
+
+we get the following output:
+
+.. code-block:: none
+
+   Information about 'choxie'
+
+   Files
+   =====
+   * Path: ../tmp/distutils2/tests/fake_dists/choxie-2.0.0.9/truffles.py
+     Hash 5e052db6a478d06bad9ae033e6bc08af, Size: 111 bytes
+   * Path: ../tmp/distutils2/tests/fake_dists/choxie-2.0.0.9/choxie/chocolate.py
+     Hash ac56bf496d8d1d26f866235b95f31030, Size: 214 bytes
+   * Path: ../tmp/distutils2/tests/fake_dists/choxie-2.0.0.9/choxie/__init__.py
+     Hash 416aab08dfa846f473129e89a7625bbc, Size: 25 bytes
+   * Path: ../tmp/distutils2/tests/fake_dists/choxie-2.0.0.9.dist-info/INSTALLER
+     Hash d41d8cd98f00b204e9800998ecf8427e, Size: 0 bytes
+   * Path: ../tmp/distutils2/tests/fake_dists/choxie-2.0.0.9.dist-info/METADATA
+     Hash 696a209967fef3c8b8f5a7bb10386385, Size: 225 bytes
+   * Path: ../tmp/distutils2/tests/fake_dists/choxie-2.0.0.9.dist-info/REQUESTED
+     Hash d41d8cd98f00b204e9800998ecf8427e, Size: 0 bytes
+   * Path: ../tmp/distutils2/tests/fake_dists/choxie-2.0.0.9.dist-info/RECORD
+     Hash None, Size: None bytes
+
+   Metadata
+   ========
+       Metadata-Version: 1.2
+                   Name: choxie
+                Version: 2.0.0.9
+               Platform: []
+     Supported-Platform: UNKNOWN
+                Summary: Chocolate with a kick!
+            Description: UNKNOWN
+               Keywords: []
+              Home-page: UNKNOWN
+                 Author: UNKNOWN
+           Author-email: UNKNOWN
+             Maintainer: UNKNOWN
+       Maintainer-email: UNKNOWN
+                License: UNKNOWN
+             Classifier: []
+           Download-URL: UNKNOWN
+         Obsoletes-Dist: ['truffles (<=0.8,>=0.5)', 'truffles (<=0.9,>=0.6)']
+            Project-URL: []
+          Provides-Dist: ['truffles (1.0)']
+          Requires-Dist: ['towel-stuff (0.1)']
+        Requires-Python: UNKNOWN
+      Requires-External: []
+
+  Extra
+  =====
+  * It was installed as a dependency
+
+
+Find out obsoleted distributions
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Now, we take tackle a different problem, we are interested in finding out
+which distributions have been obsoleted. This can be easily done as follows::
+
+  import packaging.database
+
+  # iterate over all distributions in the system
+  for dist in packaging.database.get_distributions():
+      name, version = dist.name, dist.version
+      # find out which distributions obsolete this name/version combination
+      replacements = packaging.database.obsoletes_distribution(name, version)
+      if replacements:
+          print('%r %s is obsoleted by' % (name, version),
+                ', '.join(repr(r.name) for r in replacements))
+
+This is how the output might look like:
+
+.. code-block:: none
+
+  'strawberry' 0.6 is obsoleted by 'choxie'
+  'grammar' 1.0a4 is obsoleted by 'towel-stuff'