Python 3.11: DeprecationWarning: There is no current event loop

[ErikvdVen]

When running the test suite on Python 3.11, tests with a @pytest.mark.asyncio decorator, trigger a DeprecationWarning:

.../python3.11/site-packages/pytest_asyncio/plugin.py:884: DeprecationWarning: There is no current event loop
   _loop = asyncio.get_event_loop()

[seifertm]

Which version of pytest-asyncio are you using?
Can you provide a small example that reproduces the issue?

[CherrySuryp]

Hi! I encountered same issue

Versions:

1. python 3.12
2. pytest-asyncio 0.23.4

Here's traceback

  /python3.12/site-packages/pytest_asyncio/plugin.py:656: DeprecationWarning: There is no current event loop
    old_loop = asyncio.get_event_loop()

[asl97]

I think this only happens on the older version of python?

After upgrading from python 3.11.0rc1 to 3.11.7, the warning no longer shows up.
It also doesn't show up on 3.12.1 for me.

platform win32 -- Python 3.11.7, pytest-7.4.4, pluggy-1.4.0
platform win32 -- Python 3.12.1, pytest-7.4.4, pluggy-1.4.0
plugins: asyncio-0.23.4
asyncio: mode=Mode.STRICT

The warning did shows up on older version of python before I updated it.

Which version of pytest-asyncio are you using?

platform win32 -- Python 3.11.0rc1, pytest-7.4.4, pluggy-1.4.0
plugins: asyncio-0.23.4
asyncio: mode=Mode.STRICT

Can you provide a small example that reproduces the issue?

import pytest

@pytest.mark.asyncio
async def test():
    pass

The docs has a footnote on the warning, so it would probably only show up on 3.10.0–3.10.8 and 3.11.0:
https://docs.python.org/3.11/library/asyncio-eventloop.html#asyncio.get_event_loop

Note In Python versions 3.10.0–3.10.8 and 3.11.0 this function (and other functions which use it implicitly) emitted a DeprecationWarning if there was no running event loop, even if the current loop was set on the policy. In Python versions 3.10.9, 3.11.1 and 3.12 they emit a DeprecationWarning if there is no running event loop and no current loop is set. In some future Python release this will become an error.

[michaljelonek]

When using asyncio_mode = auto I still see DeprecationWarning on Python 3.12.1, regardless whether the marker decorator is present or not. Switching to strict does resolve it, but that is not something I'd like to do, since none of our tests or fixtures are decorated. Is there something I'm missing that needs to be done when using auto mode to avoid this? Seeing that Python documentation states that in future versions this warning might become an error that is not something I'd like to ignore.

I used the same test that @asl97 provided above.

platform linux -- Python 3.12.1, pytest-7.4.4, pluggy-1.4.0
plugins: asyncio-0.23.4
asyncio: mode=Mode.AUTO
collected 1 item

tests/test_deprecation_warning.py::test PASSED                                                                                                                                                                                     [100%]

============================================================================================================ warnings summary ============================================================================================================
tests/test_deprecation_warning.py::test
  /opt/app-root/venv/lib/python3.12/site-packages/pytest_asyncio/plugin.py:656: DeprecationWarning: There is no current event loop
    old_loop = asyncio.get_event_loop()

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html

[ingwinlu]

I also still see it with 3.12.1 and strict mode:

pytest==8.0.0
pytest-asyncio==0.23.5a0

the warning no longer shows up when i remove my async fixture however that I use to init my database:

@pytest_asyncio.fixture(scope="session", autouse=True)
async def init_db(patch_get_settings):
    from ops_center.persistence import engine

    async with engine.begin() as conn:
        await conn.run_sync(SQLModel.metadata.create_all)

    yield

Alternatively the warning also disappears once I no longer specify:

@pytest.fixture(scope="session")
def event_loop_policy():
    return uvloop.EventLoopPolicy()