event loop is closed before my fixture's finalizer runs

[lars-tiede]

Consider this:

import pytest


async def foo():
    print("foo")


@pytest.yield_fixture
def my_fixture(event_loop):
    print(event_loop.is_closed()) # "False"
    event_loop.run_until_complete(foo()) # "foo"

    yield None

    print(event_loop.is_closed()) # "True"... noooo!
    event_loop.run_until_complete(foo()) # goes boom


@pytest.mark.asyncio
async def test_foo(my_fixture):
    await foo()

Run this code with py.test -s <file> and you'll see the output as indicated by the comments in the code.

The event loop is closed before my finalizer code can run. This is also the case when I write my fixture without a yield, instead adding a finalizer function.

This is weird. I'm pretty sure that this worked just fine a couple of months ago.

[Tinche]

Yeah, it's a known thing, discussed more at #29.

The recent changes simplified the event loop fixture so it would be easier to override. However, now the closing logic isn't in the fixture but in the plugin.

For 0.5, we should make the event_loop fixture a proper fixture, with cleanup logic inside, and remove the close from the plugin itself. The fixture will be a little more complex (which we can counteract with a recipe for overriding in the README) but it'd be more in the spirit of Pytest and would allow dependent fixtures to work properly (also allow overriding the scope etc).

Haven't gotten around to it just yet, patches welcome :)

[lars-tiede]

Ah, I wasn't aware of that. If I may weigh in, I think the event loop should only be closed after my_fixture ran its cleanup code. Principle of least surprise and such. How to do this best I don't know, though :)

Back to my concrete problem: the workaround you wrote here works, however I had to add asyncio.set_event_loop() for it to work for my case.

For the sake of completeness, here's your workaround including my addition of set_event_loop():

@pytest.yield_fixture
def event_loop():
    """Create an instance of the default event loop for each test case."""
    policy = asyncio.get_event_loop_policy()
    res = policy.new_event_loop()
    asyncio.set_event_loop(res)
    res._close = res.close
    res.close = lambda: None

    yield res

    res._close()

[hynek]

FWIW I believe this is the reason why upgrading pytest-asyncio broke all my integration tests that need to close their connection fixtures at the end (getting RuntimeError: Event loop is closed). Did it work by accident before or what is the rationale? Pinning at <0.4.0 for now.

[Tinche]

Hi, this issue should be solved by the latest release (0.5.0). Please close if that's the case!

[hynek]

Fixed it for me, thanks!

[kmkmjhyiiiu]

I'm still facing this issue :/

[seifertm]

@Ammadkhalid I don't mean to be rude, but your comment doesn't provide any additional information on the issue and isn't really helpful to anyone.

If you open a new Q&A discussion, we may be able to help you. If you think the bug still persists and it's a problem with pytest-asyncio, feel free to open a new issue. In any case, we can only help if you provide a minimal reproducible example.

[kmkmjhyiiiu]

@seifertm sorry for not providing information, I was creating video tutorial Setting Up Test Suits Using Pytest for a Tortoise ORM library and this is where i took advantage of this awesome Pytest plugin for asynchronous tests. I'm using this plugin version 0.21.0 However, i face the similar issue where event loop is being closed before fixture finalizer runs, https://github.com/Systembound/Just-FastApi_Tortoise-model-ORM-tests/blob/main/tests/conftest.py#L10