gh-149137: Fix PackagePath to normalize backslashes from Windows RECORD files

[starkk242]

Summary

Fixes #149137.

importlib.metadata.PackagePath extends pathlib.PurePosixPath, which treats backslashes as literal characters, not path separators. However, per the packaging spec, backslashes are valid path separators on Windows in RECORD files.

This means packages installed on Windows that use backslashes in their RECORD file (e.g. ruff) produce broken PackagePath objects:

`python

PackagePath('ruff-0.14.14.dist-info\METADATA').name
'ruff-0.14.14.dist-info\METADATA' # wrong - should be 'METADATA'
`

Fix

Override init in PackagePath to normalize backslashes to forward slashes before passing to PurePosixPath:

python def __init__(self, *args): normalized = tuple( arg.replace('\\', '/') if isinstance(arg, str) else arg for arg in args ) super().__init__(*normalized)

After the fix:

`python

PackagePath('ruff-0.14.14.dist-info\METADATA').name
'METADATA' # correct
`

The normalization is idempotent - paths already using forward slashes are unaffected.

Test plan

• Added PackagePathTests in Lib/test/test_importlib/metadata/test_main.py covering:
  • Backslash path .name returns only the filename
  • Backslash path .parts splits correctly
  • Forward-slash path is unchanged

• Issue: Incorrect handling of backslashes in RECORD file by importlib.metadata #149137

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[starkk242]

Thanks for the note! The NEWS file was already included in the initial commit but had an incorrect filename (missing the HH-MM-SS timestamp component required by blurb). Fixed in the latest push - the file is now named 2026-05-08-11-59-00.gh-issue-149137.Bp3xQz.rst following the correct blurb format.