3.11a3+ introduced the C version of abspath(), which shows incompletely normalized absolute path (see msg410068):

    >>> os.path.abspath(r'\\spam\\eggs. . .')
    '\\\\spam\\\\eggs. . .'
    >>> os.path.abspath('C:\\spam. . .')
    'C:\\spam. . .'
    >>> os.path.abspath('C:\\nul')
    'C:\\nul'

The design is efficient on startup with getpath_abspath(), but ntpath.abspath()'s result after startup should be more normalized.

Can you show various paths, before and after your change? It’s not clear to me what you’re proposing to change.

Basically, PR30571 aims for compatibility with 3.10 and earlier. Using Windows API is the easiest and the same way as them:

import os.path
paths = [
    r'C:\CON',
    r'C:\PRN',
    r'C:\AUX',
    r'C:\NUL',
    r'C:\COM1',
    r'C:\COM2',
    r'C:\COM3',
    r'C:\COM9',
    r'C:\LPT1',
    r'C:\LPT2',
    r'C:\LPT3',
    r'C:\LPT9',
    r'C:\foo. . .',
]
for path in paths:
    print(os.path.abspath(path))

"""
3.11 before
    C:\CON
    C:\PRN
    C:\AUX
    C:\NUL
    C:\COM1
    C:\COM2
    C:\COM3
    C:\COM9
    C:\LPT1
    C:\LPT2
    C:\LPT3
    C:\LPT9
    C:\foo. . .

3.11 after
    \\.\CON
    \\.\PRN
    \\.\AUX
    \\.\NUL
    \\.\COM1
    \\.\COM2
    \\.\COM3
    \\.\COM9
    \\.\LPT1
    \\.\LPT2
    \\.\LPT3
    \\.\LPT9
    C:\foo

3.10.1
    \\.\CON
    \\.\PRN
    \\.\AUX
    \\.\NUL
    \\.\COM1
    \\.\COM2
    \\.\COM3
    \\.\COM9
    \\.\LPT1
    \\.\LPT2
    \\.\LPT3
    \\.\LPT9
    C:\foo
"""

One thing to be aware of is that Windows 11 has changed the rules around these files, so here's my results with 3.10:

>>> for path in paths:
...     print(os.path.abspath(path))
...
C:\CON
C:\PRN
C:\AUX
\\.\NUL
C:\COM1
C:\COM2
C:\COM3
C:\COM9
C:\LPT1
C:\LPT2
C:\LPT3
C:\LPT9
C:\foo

But this shouldn't be an issue with the proposed (about to be merged) change.

New changeset d4e64cd4b0ea431d4e371f9b0a25f6b75a069dc1 by neonene in branch 'main':
bpo-46362: Ensure ntpath.abspath() uses the Windows API correctly (GH-30571)
https://github.com/python/cpython/commit/d4e64cd4b0ea431d4e371f9b0a25f6b75a069dc1

Thanks for the patch!

New changeset 71c0b859ae16ee748cbb050a1f4de93c04e04f83 by neonene in branch 'main':
bpo-46362: Ensure abspath() tests pass through environment variables to subprocess (GH-30595)
https://github.com/python/cpython/commit/71c0b859ae16ee748cbb050a1f4de93c04e04f83