Attempt to clarify environment marker evaluation#1988
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pradyunsg merged 17 commits intoMay 18, 2026
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Preparation for the release of packaging 25.1 revealed multiple deficiencies in the specification of environment marker evaluation. Review of the proposed amendments to resolve those deficiencies highlighted multiple other problems, including some dating from the original PEP 508 specification: * other pages still referencing PEP 508 instead of the living spec * direct reference to PEP 685 instead of the core metadata spec * the "extra" special case not being properly defined * lacking guidance to tool developers regarding what should be considered errors to disallow entirely vs issues to work around Inspired by the initial PR at pypa#1971
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ncoghlan
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Jan 10, 2026
ncoghlan
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Jan 10, 2026
ncoghlan
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Jan 25, 2026
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@henryiii Finally got back to updating this for my own comments and yours. @webknjaz @pradyunsg I think this is finally ready for a merge review. |
konstin
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May 11, 2026
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The extras thing we should fix to avoid confusing people.
woodruffw
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May 18, 2026
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Preparation for the release of packaging 25.1 revealed multiple deficiencies in the specification of environment marker evaluation. Review of the proposed amendments to resolve those deficiencies highlighted multiple other problems, including some dating from the original PEP 508 specification:
Inspired by the initial PR at #1971
discuss.python.org thread: https://discuss.python.org/t/spec-change-bugfix-dependency-specifiers-simplification-pep-508
📚 Documentation preview 📚: https://python-packaging-user-guide--1988.org.readthedocs.build/en/1988/