python-peps/pep-0631.rst

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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Status: Superseded
Type: Standards Track
Topic: Packaging
Content-Type: text/x-rst
Created: 20-Aug-2020
Post-History: 20-Aug-2020
Superseded-By: 621
Resolution: https://discuss.python.org/t/how-to-specify-dependencies-pep-508-strings-or-a-table-in-toml/5243/38
Abstract
========
This PEP specifies how to write a project's dependencies in a
``pyproject.toml`` file for packaging-related tools to consume
using the :pep:`fields defined in PEP 621 <621#dependencies-optional-dependencies>`.
.. note::
This PEP has been accepted and was merged into :pep:`621`.
Entries
=======
All dependency entries MUST be valid :pep:`PEP 508 strings <508>`.
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
- Related core metadata:
- `Requires-Dist`_
Every element MUST be an `entry <#entries>`_.
::
[project]
dependencies = [
'PyYAML ~= 5.0',
'requests[security] < 3',
'subprocess32; python_version < "3.2"',
]
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.
::
[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"',
]
Implementation
==============
Parsing
-------
::
from packaging.requirements import InvalidRequirement, Requirement
def parse_dependencies(config):
dependencies = config.get('dependencies', [])
if not isinstance(dependencies, list):
raise TypeError('Field `project.dependencies` must be an array')
for i, entry in enumerate(dependencies, 1):
if not isinstance(entry, str):
raise TypeError(f'Dependency #{i} of field `project.dependencies` must be a string')
try:
Requirement(entry)
except InvalidRequirement as e:
raise ValueError(f'Dependency #{i} of field `project.dependencies` is invalid: {e}')
return dependencies
def parse_optional_dependencies(config):
optional_dependencies = config.get('optional-dependencies', {})
if not isinstance(optional_dependencies, dict):
raise TypeError('Field `project.optional-dependencies` must be a table')
optional_dependency_entries = {}
for option, dependencies in optional_dependencies.items():
if not isinstance(dependencies, list):
raise TypeError(
f'Dependencies for option `{option}` of field '
'`project.optional-dependencies` must be an array'
)
entries = []
for i, entry in enumerate(dependencies, 1):
if not isinstance(entry, str):
raise TypeError(
f'Dependency #{i} of option `{option}` of field '
'`project.optional-dependencies` must be a string'
)
try:
Requirement(entry)
except InvalidRequirement as e:
raise ValueError(
f'Dependency #{i} of option `{option}` of field '
f'`project.optional-dependencies` is invalid: {e}'
)
else:
entries.append(entry)
optional_dependency_entries[option] = entries
return optional_dependency_entries
Metadata
--------
::
def construct_metadata_file(metadata_object):
"""
https://packaging.python.org/specifications/core-metadata/
"""
metadata_file = 'Metadata-Version: 2.1\n'
...
if metadata_object.dependencies:
# Sort dependencies to ensure reproducible builds
for dependency in sorted(metadata_object.dependencies):
metadata_file += f'Requires-Dist: {dependency}\n'
if metadata_object.optional_dependencies:
# Sort extras and dependencies to ensure reproducible builds
for option, dependencies in sorted(metadata_object.optional_dependencies.items()):
metadata_file += f'Provides-Extra: {option}\n'
for dependency in sorted(dependencies):
if ';' in dependency:
metadata_file += f'Requires-Dist: {dependency} and extra == "{option}"\n'
else:
metadata_file += f'Requires-Dist: {dependency}; extra == "{option}"\n'
...
return metadata_file
Copyright
=========
This document is placed in the public domain or under the
CC0-1.0-Universal license, whichever is more permissive.
.. _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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