ContextVar value set in async fixture is not available in test

[chbndrhnns]

It seems I cannot set a value of a ContextVar member from a fixture in pytest if that fixture is async.

In the snippet below, I expect all tests to pass but test_set_in_async_fixture which depends on a async fixture fails.

from contextvars import ContextVar

import pytest

_var = ContextVar("var", default=None)

pytestmark = [pytest.mark.anyio, ]


@pytest.fixture
def anyio_backend():
    return "asyncio"


@pytest.fixture
async def async_():
    _var.set("other")
    yield
    _var.set(None)


@pytest.fixture
def sync_():
    _var.set("other")
    yield
    _var.set(None)


async def test_None():
    assert _var.get() is None


async def test_not_None():
    _var.set("other")
    assert _var.get() == "other"
    _var.set(None)


async def test_set_in_sync_fixture(sync_):
    assert _var.get() == "other"


async def test_set_in_async_fixture(async_):
    assert _var.get() == "other"

[agronholm]

This is a shortcoming of the 3.x series, and is resolved in master. This happens in v3.x because each async fixture is run in a separate task, and is thus isolated from the actual test. The upcoming v4.0 runs each test along with its set of async fixtures within the same task.

[chbndrhnns]

Awesome, thanks for letting me know!
I noticed there is a similar problem in pytest-asyncio and the suggestion from there works here, too:

A much easier solution is to set the contextvar directly in the sync fixture — note, not async fixture, but sync: