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

[hrnciar]

Describe the bug

aiohttp fails to build with Python 3.12.0a7 due to changes in asyncio module.

asyncio.set_child_watcher(), asyncio.get_child_watcher(), asyncio.AbstractEventLoopPolicy.set_child_watcher() and asyncio.AbstractEventLoopPolicy.get_child_watcher() are deprecated and will be removed in Python 3.14. (Contributed by Kumar Aditya in gh-94597.)

To Reproduce

Build aiohttp with Python 3.12.0a7+.

Expected behavior

aiohttp builds successfully.

Logs/tracebacks

________ ERROR at setup of test_keepalive_two_requests_success[pyloop] _________

loop_factory = <class 'asyncio.unix_events._UnixDefaultEventLoopPolicy'>
fast = False, loop_debug = False

    @pytest.fixture
    def loop(loop_factory, fast, loop_debug):  # type: ignore[no-untyped-def]
        """Return an instance of the event loop."""
        policy = loop_factory()
        asyncio.set_event_loop_policy(policy)
>       with loop_context(fast=fast) as _loop:

fast       = False
loop_debug = False
loop_factory = <class 'asyncio.unix_events._UnixDefaultEventLoopPolicy'>
policy     = <asyncio.unix_events._UnixDefaultEventLoopPolicy object at 0x7f9982bf67b0>

../../BUILDROOT/python-aiohttp-3.8.4-2.fc39.x86_64/usr/lib64/python3.12/site-packages/aiohttp/pytest_plugin.py:230: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/lib64/python3.12/contextlib.py:137: in __enter__
    return next(self.gen)
        self       = <contextlib._GeneratorContextManager object at 0x7f9982bf6990>
../../BUILDROOT/python-aiohttp-3.8.4-2.fc39.x86_64/usr/lib64/python3.12/site-packages/aiohttp/test_utils.py:520: in loop_context
    loop = setup_test_loop(loop_factory)
        fast       = False
        loop_factory = <function new_event_loop at 0x7f9983f345e0>
../../BUILDROOT/python-aiohttp-3.8.4-2.fc39.x86_64/usr/lib64/python3.12/site-packages/aiohttp/test_utils.py:555: in setup_test_loop
    policy.set_child_watcher(watcher)
        loop       = <_UnixSelectorEventLoop running=False closed=False debug=False>
        loop_factory = <function new_event_loop at 0x7f9983f345e0>
        module     = 'asyncio.unix_events'
        policy     = <asyncio.unix_events._UnixDefaultEventLoopPolicy object at 0x7f9982bf67b0>
        skip_watcher = False
        watcher    = <asyncio.unix_events.ThreadedChildWatcher object at 0x7f9982bf7530>
/usr/lib64/python3.12/asyncio/unix_events.py:1496: in set_child_watcher
    warnings._deprecated("set_child_watcher",
        self       = <asyncio.unix_events._UnixDefaultEventLoopPolicy object at 0x7f9982bf67b0>
        watcher    = <asyncio.unix_events.ThreadedChildWatcher object at 0x7f9982bf7530>
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

name = 'set_child_watcher'
message = '{name!r} is deprecated as of Python 3.12 and will be removed in Python {remove}.'

    def _deprecated(name, message=_DEPRECATED_MSG, *, remove, _version=sys.version_info):
        """Warn that *name* is deprecated or should be removed.
    
        RuntimeError is raised if *remove* specifies a major/minor tuple older than
        the current Python version or the same version but past the alpha.
    
        The *message* argument is formatted with *name* and *remove* as a Python
        version (e.g. "3.11").
    
        """
        remove_formatted = f"{remove[0]}.{remove[1]}"
        if (_version[:2] > remove) or (_version[:2] == remove and _version[3] != "alpha"):
            msg = f"{name!r} was slated for removal after Python {remove_formatted} alpha"
            raise RuntimeError(msg)
        else:
            msg = message.format(name=name, remove=remove_formatted)
>           warn(msg, DeprecationWarning, stacklevel=3)
E           DeprecationWarning: 'set_child_watcher' is deprecated as of Python 3.12 and will be removed in Python 3.14.

_version   = sys.version_info(major=3, minor=12, micro=0, releaselevel='alpha', serial=7)
message    = '{name!r} is deprecated as of Python 3.12 and will be removed in Python {remove}.'
msg        = "'set_child_watcher' is deprecated as of Python 3.12 and will be removed in Python 3.14."
name       = 'set_child_watcher'
remove     = (3, 14)
remove_formatted = '3.14'

/usr/lib64/python3.12/warnings.py:529: DeprecationWarning
...
= 438 failed, 810 passed, 16 skipped, 23 deselected, 4 xfailed, 1295 errors in 102.54s (0:01:42) =

Python Version

$ python --version
Python 3.12.0a7

aiohttp Version

$ python -m pip show aiohttp
3.8.4

multidict Version

$ python -m pip show multidict
6.0.4

yarl Version

$ python -m pip show yarl
1.9.2

OS

Fedora rawhide x86_64

Related component

Server, Client

Additional context

No response

Code of Conduct

• I agree to follow the aio-libs Code of Conduct

[Dreamsorcerer]

Appears to only be used in the test, not aiohttp itself. So, just need to figure out how that test should be updated.

[martinhoyer]

Appears to only be used in the test, not aiohttp itself. So, just need to figure out how that test should be updated.

Try adding this to pyproject.toml

[tool.pytest.ini_options]
testpaths = ["./tests"]
filterwarnings = ["ignore:::.asyncio/unix_events.py:1504"]

EDIT: ah I see you're using setup.cfg for pytest config, so there instead I guess.

[Dreamsorcerer]

Or we could just fix it...

[martinhoyer]

excellent. I thought it would be a temporary workaround in order to get 3.9 released...

[Dreamsorcerer]

#7549