async fixtures are incompatible with pytest 3.7.0

[brycedrennan]

Not sure exactly what the issue is yet but test suite passes in pytest==3.6.* but fails in the very recently released pytest 3.7.0.

[Gr1N]

Got same issue, any ideas?

[brycedrennan]

For now I've just pinned my pytest to 3.6.4

[jwldk]

Same problem here. Get this error:

E TypeError: 'coroutine' object is not subscriptable

when trying to use a async fixture in a test. Works with pytest 3.6.4. Doesn't even appear to be anything related in the pytest changelog.

[JohanLorenzo]

I got a similar error. I filed this issue in pytest pytest-dev/pytest#3747 (more details in there). @RonnyPfannschmidt suggested to open an issue over here. I put up a minimal test case https://github.com/JohanLorenzo/pytest-fixture-bug-3747. Please let me know if I can provide more details.

[RonnyPfannschmidt]

@jwldk fixture definition changed in pytest to give a deprecationwarning on non-fixture usage, this issue is a collateral of that

[nicoddemus]

I investigated and here's the problem:

pytest-asyncio/pytest_asyncio/plugin.py

Lines 45 to 50 in 1ada096

	@pytest.hookimpl(hookwrapper=True)
	def pytest_fixture_setup(fixturedef, request):
	"""Adjust the event loop policy when an event loop is produced."""
	if isasyncgenfunction(fixturedef.func):
	# This is an async generator function. Wrap it accordingly.
	f = fixturedef.func

In pytest 3.7.0 fixturef.func is the "wrapped" function (which issues the warning when calling directly), which is not a coroutine/async function. This of course breaks this code.

@RonnyPfannschmidt unless we find a solution to this I'm considering reverting the wrapping code. pytest-asyncio probably is not the only plugin that will break because of this I'm afraid. 😟

[nicoddemus]

Opened a tentative PR at pytest-dev/pytest#3754