1.. _module-pw_package:
2
3==========
4pw_package
5==========
6The package module provides a mechanism to install additional tools used by
7Pigweed. Most Pigweed dependencies should be installed using
8:ref:`module-pw_env_setup`. Examples of reasons packages should be managed using
9this module instead are listed below.
10
11* The dependency is extremely large and not commonly used.
12* The dependency has a number of compatible versions and we want to allow
13  downstream projects to pick a version rather than being forced to use ours.
14* The dependency has license issues that make it complicated for Google to
15  include it directly as a submodule or distribute it as a CIPD package.
16* The dependency needs to be "installed" into the system in some manner beyond
17  just extraction and thus isn't a good match for distribution with CIPD.
18
19-----
20Usage
21-----
22The package module can be accessed through the ``pw package`` command. This
23has several subcommands.
24
25``pw package list``
26  Lists all the packages installed followed by all the packages available.
27
28``pw package install <package-name>``
29  Installs ``<package-name>``. Exactly how this works is package-dependent,
30  and packages can decide to do nothing because the package is current, do an
31  incremental update, or delete the current version and install anew. Use
32  ``--force`` to remove the package before installing.
33
34``pw package status <package-name>``
35  Indicates whether ``<packagxe-name>`` is installed.
36
37``pw package remove <package-name>``
38  Removes ``<package-name>``.
39
40-----------
41Configuring
42-----------
43
44Compatibility
45~~~~~~~~~~~~~
46Python 3
47
48Adding a New Package
49~~~~~~~~~~~~~~~~~~~~
50To add a new package create a class that subclasses ``Package`` from
51``pw_package/package_manager.py``.
52
53.. code-block:: python
54
55  class Package:
56      """Package to be installed.
57
58      Subclass this to implement installation of a specific package.
59      """
60      def __init__(self, name):
61          self._name = name
62
63      @property
64      def name(self):
65          return self._name
66
67      def install(self, path: pathlib.Path) -> None:
68          """Install the package at path.
69
70          Install the package in path. Cannot assume this directory is empty—it
71          may need to be deleted or updated.
72          """
73
74      def remove(self, path: pathlib.Path) -> None:
75          """Remove the package from path.
76
77          Removes the directory containing the package. For most packages this
78          should be sufficient to remove the package, and subclasses should not
79          need to override this package.
80          """
81          if os.path.exists(path):
82              shutil.rmtree(path)
83
84      def status(self, path: pathlib.Path) -> bool:
85          """Returns if package is installed at path and current.
86
87          This method will be skipped if the directory does not exist.
88          """
89
90There's also a helper class for retrieving specific revisions of Git
91repositories in ``pw_package/git_repo.py``.
92
93Then call ``pw_package.package_manager.register(PackageClass)`` to register
94the class with the package manager.
95
96Setting up a Project
97~~~~~~~~~~~~~~~~~~~~
98To set up the package manager for a new project create a file like below and
99add it to the ``PW_PLUGINS`` file (see :ref:`module-pw_cli` for details). This
100file is based off of ``pw_package/pigweed_packages.py``.
101
102.. code-block:: python
103
104  from pw_package import package_manager
105  # These modules register themselves so must be imported despite appearing
106  # unused.
107  from pw_package.packages import nanopb
108
109  def main(argv=None) -> int:
110      return package_manager.run(**vars(package_manager.parse_args(argv)))
111