App context not shared via pytest fixtures

[GENL]

Hi, I wonder why the quart's app context cannot be shared via fixtures.

@pytest.fixture
async def app_context(app): # app is a quart instance
    async with app.app_context() as app_context:
          await async_call() # All good: context is available here:
          yield app_context


async def test_smth(app_context):
    await async_call() # Error: not within an app context

We would expect the test to be running normally at the yield, but it doesn't like the context is lost. I'm I missing something or at least can this behavior be explained to me, please? Could it be a bug in the async-io level itself?

Thank you 🙏

Environment:

• Python version: 3.9
• Quart version: 0.18.3

[davidism]

An app context should not be pushed for an entire test, do not do with app.app_context(): yield in a fixture. Only push a context manually very locally to where that's needed.

[larsblumberg]

@davidism I'd really like to know the technical reason why trying to provide an app context via fixture won't work. As @GENL describes above, if one tries yielding the app context from a fixture, current_app wouldn't "resolve" it in the actual test using the fixture. Could you please point us to resources which explain why this is the technically the case?

[davidism]

• https://flask.palletsprojects.com/en/2.2.x/appcontext/
• https://flask.palletsprojects.com/en/2.2.x/lifecycle/#how-a-request-is-handled
• https://github.com/pallets/flask/blob/7ed89d3f9d2207c9a607f5dcdce106c0278e1332/src/flask/ctx.py#L357-L365

current_app wouldn't "resolve" it in the actual test using the fixture

I'm not entirely sure what you're trying to say, but I'm not clear why you think that either. The context is active as long as the with block hasn't ended, and yielding suspends a function, it doesn't end it.

[larsblumberg]

I'm not entirely sure what you're trying to say, but I'm not clear why you think that either. The context is active as long as the with block hasn't ended, and yielding suspends a function, it doesn't end it.

Sorry for my poor wording. I was referring to the example in the OP:

@pytest.fixture
async def app_context(app): # app is a quart instance
    async with app.app_context() as app_context:
          await async_call() # All good: context is available here:
          yield app_context


async def test_smth(app_context):
    await async_call() # raises exception: not within an app context

The moment yield app_context is executed and flow control is given to test_smth(), the app context is no longer available. An exception is raised by quart saying that we are not within an app context. And that is despite the yield app_context being executed within async with app.app_context() as app_context:. Maybe this is a particularity to the way how async tests are executed by pytest?

[latk]

Duplicate of #149? Seems like the problem is the async fixture, not how Quart contexts work.