zlib extractall can not extract zip because of '/' in namelist

[bohdansolovey]

Bug report

Bug description:

I am trying to extract all members from zipfile, and this zipfile is created by my code. In python3.11 and MacOS default archiver I can extract this file, but using 3.12 I see an error because of '/' in the zipfile.namelist()
debug_data_1_analyze.zip

with open('./myarchive.zip', 'rb') as fh:
    z = zipfile.ZipFile(fh)
    z.extractall('.')

CPython versions tested on:

3.11, 3.12

Operating systems tested on:

Linux

Linked PRs

• gh-112795: Allow / folder in a zipfile #112932
• [3.12] gh-112795: Allow / folder in a zipfile (GH-112932) #113789
• gh-112795: Move the test for ZipFile into the core tests for zipfile. #116823
• [3.12] gh-112795: Move the test for ZipFile into the core tests for zipfile. (GH-116823) #116830

[pkatz100]

I'm seeing it on Windows 11, Python versions 3.12 and the pre-release 3.13.

Also, I'm trying to extract from an archive that is generated by Atlassian's Confluence Wiki product (which exports wiki pages in a .zip file), so don't have control over the contents of the namelist.

[mattprodani]

Related to this change that adds an empty name check after sanitizing: #98286

(the addition of if not arcname clause below)

cpython/Lib/zipfile/__init__.py

Lines 1765 to 1776 in 16448ca

	# interpret absolute pathname as relative, remove drive letter or
	# UNC path, redundant separators, "." and ".." components.
	arcname = os.path.splitdrive(arcname)[1]
	invalid_path_parts = ('', os.path.curdir, os.path.pardir)
	arcname = os.path.sep.join(x for x in arcname.split(os.path.sep)
	if x not in invalid_path_parts)
	if os.path.sep == '\\':
	# filter illegal characters on Windows
	arcname = self._sanitize_windows_name(arcname, os.path.sep)
	if not arcname:
	raise ValueError("Empty filename.")

The 'interpret absolute paths as relative' part doesn't apply on this case because splitting the string on / returns an empty list. Prior to the change, when arcname was empty the result would join to ./ so it worked out. A / entry in a zip file seems odd but if it commonly works with other tools it might make sense to take care of.

[gpshead]

Thanks for the bug report and thanks for the fix (and in particular the regression test!) @aisk. merged in main, the 3.12 PR should automerge and close this issue soon.