python-peps/pep-0631.rst

PEP: 631
Title: Dependency specification in pyproject.toml based on PEP 508
Author: Ofek Lev <ofekmeister@gmail.com>
Sponsor: Paul Ganssle <paul@ganssle.io>
Discussions-To: https://discuss.python.org/t/5018
Status: Draft
Type: Standards Track
Content-Type: text/x-rst
Created: 20-Aug-2020
Post-History: 20-Aug-2020


Abstract
========

This PEP specifies how to write a project's dependencies in a
``pyproject.toml`` file for packaging-related tools to consume
using the `fields defined in PEP 621`_.

Entries
=======

All dependency entries MUST be valid `PEP 508 strings`_.

Build backends SHOULD abort at load time for any parsing errors.

::

    from packaging.requirements import InvalidRequirement, Requirement

    ...

    try:
        Requirement(entry)
    except InvalidRequirement:
        # exit

Specification
=============

dependencies
------------

- Format: array of strings or inline tables
- Related core metadata:

  - `Requires-Dist`_

Every element SHOULD be an `entry <#entries>`_.

::

    [project]
    dependencies = [
      'PyYAML ~= 5.0',
      'requests[security] < 3',
      'subprocess32; python_version < "3.2"',
    ]

Any element MAY be an inline table to support possible future functionality.
Backends MUST silently ignore these until the specification is extended.

optional-dependencies
---------------------

- Format: table
- Related core metadata:

  - `Provides-Extra`_
  - `Requires-Dist`_

Each key is the name of the provided option, with each value being the same type as
the `dependencies <#dependencies>`_ field i.e. an array of strings or inline tables.

::

    [project.optional-dependencies]
    tests = [
      'coverage>=5.0.3',
      'pytest',
      'pytest-benchmark[histogram]>=3.2.1',
    ]

Example
=======

This is a real-world example port of what `docker-compose`_ defines.

::

    [project]
    dependencies = [
      'cached-property >= 1.2.0, < 2',
      'distro >= 1.5.0, < 2',
      'docker[ssh] >= 4.2.2, < 5',
      'dockerpty >= 0.4.1, < 1',
      'docopt >= 0.6.1, < 1',
      'jsonschema >= 2.5.1, < 4',
      'PyYAML >= 3.10, < 6',
      'python-dotenv >= 0.13.0, < 1',
      'requests >= 2.20.0, < 3',
      'texttable >= 0.9.0, < 2',
      'websocket-client >= 0.32.0, < 1',

      # Conditional
      'backports.shutil_get_terminal_size == 1.0.0; python_version < "3.3"',
      'backports.ssl_match_hostname >= 3.5, < 4; python_version < "3.5"',
      'colorama >= 0.4, < 1; sys_platform == "win32"',
      'enum34 >= 1.0.4, < 2; python_version < "3.4"',
      'ipaddress >= 1.0.16, < 2; python_version < "3.3"',
      'subprocess32 >= 3.5.4, < 4; python_version < "3.2"',
    ]

    [project.optional-dependencies]
    socks = [ 'PySocks >= 1.5.6, != 1.5.7, < 2' ]
    tests = [
      'ddt >= 1.2.2, < 2',
      'pytest < 6',
      'mock >= 1.0.1, < 4; python_version < "3.4"',
    ]

Copyright
=========

This document is placed in the public domain or under the
CC0-1.0-Universal license, whichever is more permissive.


.. _fields defined in PEP 621: https://www.python.org/dev/peps/pep-0621/#dependencies-optional-dependencies
.. _PEP 508 strings: https://www.python.org/dev/peps/pep-0508/
.. _Requires-Dist: https://packaging.python.org/specifications/core-metadata/#requires-dist-multiple-use
.. _Provides-Extra: https://packaging.python.org/specifications/core-metadata/#provides-extra-multiple-use
.. _docker-compose: https://github.com/docker/compose/blob/789bfb0e8b2e61f15f423d371508b698c64b057f/setup.py#L28-L61

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