The behaviour of os.path.normpath appears to have changed between Python 3.10/Python 3.11.0a2 and 3.11.0a3+.
I don't see anything mentioned in https://docs.python.org/3.11/whatsnew/3.11.html
Is this intentional?
Old behaviour:
Python 3.10.1 (v3.10.1:2cd268a3a9, Dec  6 2021, 14:28:59) [Clang 13.0.0 (clang-1300.0.29.3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from os.path import normpath
>>> normpath('handbook/../../Tests/image.png')
'../Tests/image.png'
>>>
Python 3.11.0a2 (main, Dec 30 2021, 21:22:15) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from os.path import normpath
>>> normpath('handbook/../../Tests/image.png')
'../Tests/image.png'
>>>
New behaviour:
Python 3.11.0a3+ (heads/main:af6b406, Dec  9 2021, 15:34:48) [Clang 13.0.0 (clang-1300.0.29.3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from os.path import normpath
>>> normpath('handbook/../../Tests/image.png')
'Tests/image.png'
>>>
Python 3.11.0a3+ (heads/main:8d7644f, Dec 30 2021, 21:32:51) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from os.path import normpath
>>> normpath('handbook/../../Tests/image.png')
'Tests/image.png'
>>>
(Found in https://github.com/sphinx-doc/sphinx/issues/10030.)

The issue could be related to 99fcf1505218464c489d419d4500f126b6d6dc28 / bpo-45582.

git bisect between v3.11.0a2 and v3.11.0a3 points to the same commit, 99fcf1505218464c489d419d4500f126b6d6dc28.

Yep, it's a bug and should be fixed.
I'm still not back coding yet, but I'll get to it once I am if nobody else gets there first. This is going to affect getpath.py in the native implementation, so it ought to be fixed there (and we need tests for this case, since it's apparently a gap).

Here's a branch with a passing ntpath.normpath test and a failing posixpath.normpath test:
https://github.com/hugovk/cpython/tree/issue-46208-tests
https://github.com/hugovk/cpython/commit/d7e8da179adce51a8f63d2dbd062a272dda826bc

>Here's a branch with a passing ntpath.normpath test and a failing posixpath.normpath test:
I took the test cases for my PR, thanks.
On Windows machine, ntpath fails and posixpath passes. It seems that the passing one is tested with pure python code.

I'm happy with PR 30362 now - any other comments before we merge?

New changeset 9c5fa9c97c5c5336e60e4ae7a2e6e3f67acedfc7 by neonene in branch 'main':
bpo-46208: Fix normalization of relative paths in _Py_normpath()/os.path.normpath (GH-30362)
https://github.com/python/cpython/commit/9c5fa9c97c5c5336e60e4ae7a2e6e3f67acedfc7

pull_requests: + pull_request28576
stage: patch review

messages: + msg409419