Dynamically calling async fixture causes a runtime error saying "This event loop is already running"

There seems to be a bug with how request.getfixturevalue(argname) interacts with pytest-asyncio. Calling the function leads to a runtime error saying the event loop is already running. If you change it from being dynamically called to being fixed in the function definition, it works as expected.

Platform Info:

platform win32 -- Python 3.7.2, pytest-4.2.0, py-1.7.0, pluggy-0.8.1
plugins: asyncio-0.11.0.dev0

Test fixture that can be used in both dynamic/fixed cases:

@pytest.fixture
async def async_fixture():
    yield 'Hi from async_fixture()!'

Successful fixed function argument fixture test:

@pytest.mark.asyncio
async def test_async_fixture_fixed(async_fixture):
    assert async_fixture == 'Hi from async_fixture()!'

Failed dynamic fixture test:

@pytest.mark.asyncio
async def test_async_fixture_dynamic(request):
    async_fixture = request.getfixturevalue('async_fixture')
    assert async_fixture == 'Hi from async_fixture()!'

Failed test trace-back:

================================== FAILURES ===================================
_________________________ test_async_fixture_dynamic __________________________

request = <FixtureRequest for <Function test_async_fixture_dynamic>>

    @pytest.mark.asyncio
    async def test_async_fixture_dynamic(request):
>       async_fixture = request.getfixturevalue('async_fixture')

tests\test_app_factory.py:52: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
venv\lib\site-packages\_pytest\fixtures.py:478: in getfixturevalue
    return self._get_active_fixturedef(argname).cached_result[0]
venv\lib\site-packages\_pytest\fixtures.py:501: in _get_active_fixturedef
    self._compute_fixture_value(fixturedef)
venv\lib\site-packages\_pytest\fixtures.py:586: in _compute_fixture_value
    fixturedef.execute(request=subrequest)
venv\lib\site-packages\_pytest\fixtures.py:881: in execute
    return hook.pytest_fixture_setup(fixturedef=self, request=request)
venv\lib\site-packages\pluggy\hooks.py:284: in __call__
    return self._hookexec(self, self.get_hookimpls(), kwargs)
venv\lib\site-packages\pluggy\manager.py:68: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
venv\lib\site-packages\pluggy\manager.py:62: in <lambda>
    firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
venv\lib\site-packages\_pytest\fixtures.py:923: in pytest_fixture_setup
    result = call_fixture_func(fixturefunc, request, kwargs)
venv\lib\site-packages\_pytest\fixtures.py:782: in call_fixture_func
    res = fixturefunc(**kwargs)
..\pytest-asyncio\pytest_asyncio\plugin.py:97: in wrapper
    return loop.run_until_complete(setup())
C:\Users\ykuzm\AppData\Local\Programs\Python\Python37\lib\asyncio\base_events.py:571: in run_until_complete
    self.run_forever()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <_WindowsSelectorEventLoop running=False closed=False debug=False>

    def run_forever(self):
        """Run until stop() is called."""
        self._check_closed()
        if self.is_running():
>           raise RuntimeError('This event loop is already running')
E           RuntimeError: This event loop is already running

Start by reproducing the dynamic and fixed fixture cases in tests/test_app_factory.py, then inspect pytest_asyncio/plugin.py around the wrapper at line 97 and pytest's request.getfixturevalue path shown in the traceback. Done means the dynamic async fixture test completes without the event-loop runtime error and returns the expected fixture value.