loop_scope default

[oliver-sanders]

(in relation to #706 and other related issues)

Can I get the fixture loop_scope to default to the fixture's scope?

Description

If I have a fixture that provides an async resource like so:

@pytest.fixture(scope='module')
async def my_async_fixture():
    yield my_async_resource()

I need to declare it with pytest_asyncio.fixture and define loop_scope to match the fixture scope (see 0.23 migration guide):

@pytest_asyncio.fixture(scope='module', loop_scope='module')
async def my_async_fixture():
    yield my_async_resource()

But the fixture scope is a safe and sensible default for the loop_scope in my work. Lesser scopes typically won't work because the point of the fixture is to manage an async resource (not just to run async code before/after the test). The point of higher scopes in general is to create resources that can be shared between tests, so we accept the isolation implications when we write them and are happy with loop_scope = scope as a default (we can always override it if we have a use case to).

This loop_scope parameter is easily omitted, and the pytest_asyncio.fixture decorator is less known to contributors making this pattern a bit of a pain point. Is there a way I can make the loop_scope default to the fixture scope so we can continue to use @pytest.fixture(scope=<scope>) as before?

Note, I can't use the asyncio_default_fixture_loop_scope because I have fixtures with session, module, class and function scopes.

Proposal

If this can't be done at present, would it make sense to provide a asyncio_default_fixture_loop_scope = scope option?

[seifertm]

That's an interesting point!

We didn't consider an option to always match loop_scope to scope. Essentially, this is the behavior when asyncio_default_fixture_loop_scope is unset, but leaving it unset gives a deprecation warning.

[EdgyEdgemond]

This would be super useful, I have a third party library that provides an async session fixture, but if I configure asyncio_default_fixture_loop_scope that starts breaking, as the thirdparty library is just using @fixture(scope="session").

It shouldn't have to enforce pytest_asyncio as a dependency to support me using pytest_asyncio. That would just break people not using pytest_asyncio etc.