Python 3.14 compatibility

[webknjaz]

Currently, a bunch of tests are failing in CI under Python 3.14. They need to be inspected and addressed. I don't know if the patch would need test-only changes or more runtime compatibility fixes.

This might be a good first issue for somebody with network programming + multi-env testing + multi-python compat experience.

[thearpankumar]

@webknjaz assign me this issue

[Agentx402]

Thanks for bringing this issue to light! It sounds like a great opportunity for someone looking to dive into multi-Python compatibility. I recommend checking out the Python documentation on version-specific changes to help identify any potential breaking changes that could be affecting your tests. Keep up the good work!

[webknjaz]

@thearpankumar assigning issues to drive-by contributors is uncommon in open source. If you want to send a patch, file a PR.

[thearpankumar]

@webknjaz Hey, i understand but i am a regular contributor if you see my profile but its ok. its general practice to assign the issue , if you don't want to follow it i don't think i will contribute then, thank you.

[webknjaz]

You can try and we'll see. I disagree that the practice is common, though. It most certainly is not. It might be different for cases when a contributor has a history of submitting PRs into a project and is known within that scope. First time contributing is almost always a drive-by by definition because those usually address a small thing once and never come back again.

[thearpankumar]

@webknjaz so i checked the CI run, tox in 3.12 windows-2025 is also failing with 3.14 builds, i need to check what is up with that locally, what are version changes but any directions which way i should look ??

[webknjaz]

Some tests are flaky. And part of them may be addressed by solving #768 (smbd tried and got stuck in #772, it seems). There's also #770 and #777 that might help once complete.

When a flaky test fails a pytest run (through tox), the CI job will rerun it with more verbosity (and purposefully fail that rerun step even if the test succeeds).
When a job fails (and is not marked as allowed to fail), the CI will auto-cancel other jobs in the same matrix.

Some of the suppressed warnings turned into errors in Python 3.14, I think. This might be the root cause for those failures. Somebody need to check that.

This seems like a legitimate failure you should be able to reproduce locally: https://github.com/cherrypy/cheroot/actions/runs/18230474859/job/51912515655#step:21:423 / https://github.com/cherrypy/cheroot/actions/runs/18230474859/job/51912516257#step:20:479.

I recommend you to focus on one small thing at a time and try to understand what causes it, whether it's reproducible consistently and so on. Document your findings and suggest small fixes where possible. Since some problems are difficult to grasp, the fixes might be difficult to judge and you'll need to get into detail when explaining what's broken and why you think the solution is right.

[thearpankumar]

@webknjaz the CI have been fixed and this was my approach

Root Cause: Python 3.14 changed the default multiprocessing start method from fork to forkserver on Unix platforms, breaking pytest-xdist parallel execution.

Solution:

1. Multiprocessing Fix (cheroot/test/conftest.py):
   - Force fork method on Python 3.14+ Unix systems
   - Skip on Windows (doesn't support fork)
   - Used contextlib.suppress for clean exception handling
2. IOBase Warning Filter (pytest.ini):
   - Updated regex from "Exception ignored in." to "Exception ignored.*"
   - Python 3.14 changed error format to "Exception ignored while calling deallocator"
3. Pre-commit Config (.pre-commit-config.yaml):
   - Set flake8 language_version: python3.11 to match CI
   - Prevents Python 3.14 incompatibility errors in flake8-annotations plugin

Result: All tests pass on Python 3.14 (Linux/Windows), fully backward compatible with 3.8-3.13.

CI run link - https://github.com/thearpankumar/cheroot/actions/runs/18244794980

[thearpankumar]

@webknjaz Should i create the PR now or you want any changes ??