Zipfile module doesn't replace `os.altsep` in filenames in some cases

[pR0Ps]

The zipfile module currently doesn't replace os.altsep with / in filename in cases where os.altsep is not None and not "/".

I'm not currently aware of any cases where os.altsep is not None or "/", so I don't think this is currently causing any issues, but it's at least not consistent with the documentation which states that os.altsep is "An alternative character used by the operating system to separate pathname components".

To reproduce the issue, the code below manually sets os.sep and os.altsep to be the normal Windows values, then swaps them. This should have no effect on the resulting zip file since the values should both be treated as valid path separators.

import io
import ntpath
import os
import zipfile

def show_zip():
    zf = zipfile.ZipFile(io.BytesIO(), 'w')
    zf.writestr("a/b/", "")
    zf.writestr("a/b\\", "")
    zf.writestr("a\\b/", "")
    zf.writestr("a\\b\\", "")
    print([x.filename for x in zf.infolist()])

os.sep = ntpath.sep
os.altsep = ntpath.altsep
show_zip()

os.altsep, os.sep = os.sep, os.altsep
show_zip()

Expected output:

['a/b/', 'a/b/', 'a/b/', 'a/b/']
['a/b/', 'a/b/', 'a/b/', 'a/b/']

Actual output:

['a/b/', 'a/b/', 'a/b/', 'a/b/']
['a/b/', 'a/b\\', 'a\\b/', 'a\\b\\']

Environment: Python 3.11.0a7+ (heads/main:56f9844014, May 2 2022, 15:22:18) [Clang 11.0.0 (clang-1100.0.33.17)] on darwin

Linked PRs

• GH-92184: Convert os.altsep to '/' in filenames when creating ZipInfo objects #92185

[gpshead]

i'm not convinced this was really worthwhile... given there are no known applicable platforms, but the logic in the PR was trivial enough and is pedantically correct for consistency. It is set to automerge. Thanks!

[pR0Ps]

I'm not convinced this was really worthwhile

Yeah, I'm with you there. It was more just something I noticed while fixing something else and figured I'd make a quick drive-by commit to fix. Thanks for merging it!