DeprecationWarning: 'AbstractChildWatcher' is deprecated as of Python 3.12 and will be removed in Python 3.14.

[rmartin16]

Describe the bug

DeprecationWarning for AbstractChildWatcher from Python 3.12.0a7.

/home/russell/github/beeware/briefcase/venv-3.12.0a7-briefcase/lib/python3.12/site-packages/gbulb/glib_events.py:54: DeprecationWarning: 'AbstractChildWatcher' is deprecated as of Python 3.12 and will be removed in Python 3.14.
  class GLibChildWatcher(AbstractChildWatcher):

Steps to reproduce

briefcase dev on Python 3.12.0a7 or later; may require a debug compilation of Python.

Expected behavior

DeprecationWarning is not logged for AbstractChildWatcher.

Screenshots

No response

Environment

• Operating System: pop os 22.04
• Python version: 3.12.0a7
• Software versions:
  • Briefcase: 0.3.14.dev78+g3f8b8979

Logs

No response

Additional context

No response

[freakboy3742]

From what I can tell, the GLibChildWatcher can be directly replaced with asyncio.PidfdChildWatcher - but we need to wait until Python 3.9 is our minimum supported version before we can make that change.

[eichin]

FYI just ran into this on freshly installed just-pre-24.04 system, running through the beeware tutorial, specifically during https://docs.beeware.org/en/latest/tutorial/tutorial-1.html#run-the-app-in-developer-mode

Successfully installed gbulb-0.6.4 iniconfig-2.0.0 pluggy-1.4.0 pycairo-1.26.0 pygobject-3.48.2 pytest-8.1.1 toga-core-0.4.2 toga-gtk-0.4.2 travertino-0.3.0
[helloworld] Starting in dev mode...
===========================================================================
/home/eichin/tmp/beeware-tutorial/beeware-venv/lib/python3.12/site-packages/gbulb/glib_events.py:54: DeprecationWarning: 'AbstractChildWatcher' is deprecated as of Python 3.12 and will be removed in Python 3.14.
  class GLibChildWatcher(AbstractChildWatcher):

This is with a release version of python, ubuntu package python3 3.12.3-0ubuntu1, the venv python identifies as

Python 3.12.3 (main, Apr 10 2024, 05:33:47) [GCC 13.2.0] on linux

(but that's the exact same thing the system one does, so no development version needed.)

I would generally say "eh, deprecated for two major releases, plenty of time" but on the other hand, this is showing up right when the beeware tutorial is starting to get interesting, so it might be worth some extra consideration. (That might not be possible, either, per the #76 (comment) comment above.)

[freakboy3742]

Completely agreed that with the release of Ubuntu 24.04, this is starting to get a little urgent, as is #116 and #117.

As for the replacement strategy: I'm not opposed to an if sys.version_info <= 3.9 block if that gets us around the problem. I haven't looked recently to see how feasible that sort of replacement would be.