Python 3.10.9: DeprecationWarning: There is no current event loop

[jakob-keller]

CPython 3.10.9 was released this week and tweaked the DeprecationWarning of asyncio.get_event_loop(): python/cpython#93453

As a consequence tests are now failing again, despite #214.

[seifertm]

Thanks for reporting this.

The DeprecationWarning is triggered by pytest_fixture_setup. Apparently, pytest-asyncio tries to clean any existing event loop and replace the current loop with the one provided by the event_loop fixture. This means the warning is triggered every time pytest-asyncio is used. As a result, users receive a DeprecationWarning for one of their test dependencies. This can break their tests, if they use -W error.

Pytest-asyncio tries to close any unclosed event loop before running a test. This is convenient for the user, but it means that users don't notice faulty event loop handling in their code. If users need to work with event loops they should also take care to dispose them properly. Pytest-asyncio should not try to be smarter and do it for them.

In my opinion the correct solution is to raise a warning or an error when the user tries to use pytest-asyncio with a running or unclosed event loop. However, this would be a breaking change and I prefer to address this issue in a patch release.

To avoid having to deal with unnecessary DeprecationWarnings, my suggestion is to simply ignore the warnings, until we implement the breaking change mentioned above.

[jakob-keller]

To avoid having to deal with unnecessary DeprecationWarnings, my suggestion is to simply ignore the warnings, until we implement the breaking change mentioned above.

I have done this and it works like a charm, at least until we migrate to Python 3.12.

[jakob-keller]

Wow, that was quick! pytest-asyncio 0.20.3 fixes this issue for me. Warnings do not need to be ignored in my project anymore.

@seifertm Tausend Dank!

[seifertm]

You're welcome. I bet this affects a lot of users.

I'll reopen the issue, because we need to find a permanent solution that doesn't break in Python 3.12.