Async fixtures request wrong event loop

[seifertm]

Fixes a bug that caused tests to run in the wrong event loop when requesting larger-scoped fixtures in a narrower-scoped test.

Previously, pytest-asyncio relied on marks applied to pytest Collectors (e.g. classes and modules) to determine the loop scope. This logic is no longer applicable for fixtures, because pytest-asyncio now relies on the asyncio mark applied to tests. As a result, fixtures were looking for an "asyncio" mark on surrounding collectors to no avail and defaulted to choosing a function-scoped loop.

This patch chooses the loop scope based on the fixture scope.

Resolves #658
Resolves #670

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ee1589f) 94.72% compared to head (fbc32e0) 94.75%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #675      +/-   ##
==========================================
+ Coverage   94.72%   94.75%   +0.03%     
==========================================
  Files           2        2              
  Lines         455      458       +3     
  Branches       92       93       +1     
==========================================
+ Hits          431      434       +3     
  Misses         15       15              
  Partials        9        9              

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[Mexflubber]

After this change I'm getting the new warning you added.

Replacing the event_loop fixture with a custom implementation is deprecated and will lead to errors in the future ...

On my test setup I initialize a database for some end-to-end testing between my api and my db. Some tests send a put request to the API, then the API writes to the DB. And in the following test I send a get request to the API, expecting the data to be there.

To achieve this I'm using pytest_postgresql and I'm using the databaseJanitor to setup a db from a schema in file (won't cover how to do it here). By using scope session on my db-init I guarantee my DB will stay up through the entire test suite.

So my current setup code is as follows

@pytest_asyncio.fixture(scope="session")
def event_loop(request):
    loop = asyncio._get_running_loop() or asyncio.new_event_loop()
    yield loop
    loop.close()

@pytest_asyncio.fixture(scope="session", autouse=True)
async def connection_test(test_db):
    pg_host = test_db.host
    pg_port = test_db.port
    pg_user = test_db.user
    pg_db = test_db.dbname
    pg_password = test_db.password

    with DatabaseJanitor(pg_user, pg_host, pg_port, pg_db, test_db.version, pg_password):
        connection_str = f"postgresql+asyncpg://{pg_user}:@{pg_host}:{pg_port}/{pg_db}"
        database_session.init(connection_str)
        yield
        await database_session.close()

I have no idea how to get rid of the warning while still making my tests work.

Could you please help me?

Thanks,
Aldo

[Mexflubber]

@seifertm any chance you can take a look at my previous comment?

[seifertm]

@Mexflubber I'm not sure which version of pytest-asyncio you're using. The latest stable version is pytest-asyncio v0.21.1, which doesn't have the warning. If you're using the yanked v0.22, you cannot do anything about it. If you're using v0.23.0a1, I would expect that you can simply delete your current event_loop fixture.

Starting from v0.23, each pytest collector (i.e. classes, modules, packages, and the session) have their own event loop. Async tests and fixtures run in the event loop that matches their scope. That means connection_test would run in the event_loop provided by the session, because it's a session-scoped fixture.

Async tests run in the scope provided by the scope keyword argument to @pytest.mark.asyncio(…). If no scope is given for a test, they will run in a function-scoped event loop.

Issue #677 is meant to bring the documentation up to speed before the v0.23 release.