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PEP 825: Collected updates - #5110

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warsaw merged 3 commits into
python:mainfrom
wheelnext:pep-825-integration
Sep 1, 2026
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PEP 825: Collected updates#5110
warsaw merged 3 commits into
python:mainfrom
wheelnext:pep-825-integration

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@konstin

@konstin konstin commented Aug 31, 2026

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This PR collates several updates to PEP 825 (https://discuss.python.org/t/pep-825-wheel-variants-package-format-split-from-pep-817/106196).

Change History

26-Aug-2026

  • Added pep825-metadata-consistency as an appendix, setting out
    why the metadata consistency_ requirements are justified and what
    they cost. Summarized the metadata consistency argument in the
    Rationale.
  • Closed the open issue on the use of variant environment markers.
    The investigation in the appendix settles the question in favour of
    markers, so the Open Issues section has been removed and the
    reasoning recorded in the Rationale instead.
  • Removed grouping by build numbers, instead relegating them to
    tie-breaking along with other wheel properties. This reverts a
    potential change in behavior for non-variant wheels.
  • Added a high-level overview to "variant ordering and selection",
    clarified that the ordering of the lists used in the algorithm is
    from the most preferable to the least preferable and that the
    ordering by platform compatibility tags is not changed.

Add peps/pep-0825/appendix-metadata-consistency.rst, setting out why the
metadata consistency requirements are justified, what they cost, and what
they deliberately leave open. It covers the 2024 "Enforcing consistent
metadata" DPO thread and the status of its two prominent cases, the resolver
cost that forced dependency divergence would impose, and why divergent variant
metadata specifically is incoherent rather than expressive.

It includes a survey of which build backends can emit
`Dynamic: Requires-Dist` in wheel METADATA, which establishes that the
alternative to variant environment markers is reachable today only through
`setuptools` with a `setup.py`.

Summarize the argument in a new "Variant metadata consistency" subsection
of the Rationale, and cross-reference the appendix from the specification.

Close the open issue on the use of variant environment markers. The
investigation settles the question in favour of markers, so the Open
Issues section is removed and the reasoning is recorded at the end of the
"Variant environment markers" rationale instead.
@konstin
konstin requested review from a team, dstufft and warsaw as code owners August 31, 2026 19:31
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read-the-docs-community Bot commented Aug 31, 2026

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Documentation build overview

📚 pep-previews | 🛠️ Build #34330814 | 📁 Comparing 21e8057 against latest (fa5792c)

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+ pep-0825/appendix-metadata-consistency/index.html
± pep-0825/index.html

@mgorny
mgorny force-pushed the pep-825-integration branch from a6278c6 to 628343c Compare September 1, 2026 05:30
Provide a high-level description of how ordering works and what it is
meant to achieve, in addition to the precise algorithm provided right
now.  Add clarifications to the algorithm, to make it clear in what
order the lists are actually arranged.

Signed-off-by: Michał Górny <mgorny@quansight.com>
Co-authored-by: konstin <konstin@mailbox.org>
Co-authored-by: rgommers <ralf.gommers@gmail.com>
Signed-off-by: Michał Górny <mgorny@quansight.com>
@mgorny
mgorny force-pushed the pep-825-integration branch from 628343c to 13318e2 Compare September 1, 2026 07:39
Comment thread peps/pep-0825/appendix-metadata-consistency.rst Outdated
Co-authored-by: konstin <konstin@mailbox.org>
Signed-off-by: Michał Górny <mgorny@quansight.com>
@warsaw
warsaw merged commit 6a3a346 into python:main Sep 1, 2026
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5 participants