pathlib.Path.with_suffix(None) became allowed in Python 3.13b1

[bluetech]

Bug report

Bug description:

In Python 3.13b1 (compared to Python 3.12 and earlier), the behavior of pathlib.Path.with_suffix(None) changed from raising an incidental TypeError to removing the suffix. This casues a certain test in pytest to fail. I am going to fix pytest to not rely on this in any case, but I think pathlib should either:

• Restore the previous behavior if it was unintended, or
• Update the doc that None is now accepted. Currently it says " If the suffix is an empty string, the original suffix is removed".

CPython versions tested on:

3.12, 3.13

Operating systems tested on:

Linux

Linked PRs

• GH-119113: Raise TypeError from pathlib.PurePath.with_suffix(None) #119124
• [3.13] GH-119113: Raise TypeError from pathlib.PurePath.with_suffix(None) (GH-119124) #119183

[nineteendo]

Bisected to 19a1fc1

cpython/Lib/pathlib/_abc.py

Line 208 in 100c7ab

if not suffix:

I guess we could replace that with this:

if suffix == '':

But we usually don't go out of our way to raise type errors.

[barneygale]

Thanks for reporting! Should be fixed in 3.13 beta 2.