How do I autouse a fixture only when another fixture has been requested?

[oakkitten]

The title might sound like this is an XY problem, so let me explain.

I have a session scope fixture app, and a few other wide scope fixtures that depend on it. Also I have a fixture that does some app cleanup and I want it to run after each test. So I've got tests like this:

def test_foo(app, cleanup):
    ...

def test_bar(app_with_profile_loaded, cleanup):
    ...

Now, I don't want to say cleanup in each test function arguments so I want to make it used automatically. However, if I do

@pytest.fixture(autouse=True)
def cleanup():
    ...

then cleanup will also get called for tests that do not ask for app, which could break cleanup, and if I do

@pytest.fixture(autouse=True)
def cleanup(app):
    ...

the app will be also constructed for tests that that do not ask for it, which is also problematic.

I could do the following, which should work,

@pytest.fixture(autouse=True)
def cleanup(request):
    if "app" in request.fixturenames:
        ...

but I will then have cleanup for every test in --setup-plan. Is there a better way?

[brizjin]

Probably, your app fixture is session level. That is why you need separate fixture, function level, which will clean everything after each test and do no create app each test. You can solve it, with creating other function level fixture, which will sent app session level and then clean app everything. Then use app-function level everywhere in test it needs, and it will cleanup after test and do not destroy app object. And you will not have autouse fixtures, tests which no need app will not use it:

@fixture(scope='session')
def app_session():
    app = create_app()
    with app.app_context():
        yield app


@fixture
def app(app_session):
    yield app_session
    cleanup()

[oakkitten]

Hum, that works, but then I would have to define similar constructs for all fixtures that depend on app. I think I would prefer the request trick to this.