Cannot run the event loop when using pytest asyncio tests after Playwright tests

[medihack]

When I run async tests using pytest-asyncio (marked with @pytest.mark.asyncio) after integration tests using playwright-pytest (which only uses playwright.sync_api calls), then those tests fail with the below error message. If I run the async tests before the integration tests then everything works fine.
Why is there still some event loop running after the integration tests finished even if I don't use async calls with Playwright?

Edit:
After some research, it seems to be a known problem, which is simply an incompatibility between pytest-asyncio and playwright-pytest. playwright-pytest seems to start an event loop (even when using the sync API) and pytest-asyncio doesn't get along with an already started one.

See pytest-dev/pytest-asyncio#359

args = (), kwargs = {}, coro = <coroutine object test_start_transmit_file at 0x7f1c08343f40>
task = <Task pending name='Task-10' coro=<test_start_transmit_file() running at /workspaces/adit/adit/core/tests/utils/test_file_transmit.py:18>>

    @functools.wraps(func)
    def inner(*args, **kwargs):
        coro = func(*args, **kwargs)
        if not inspect.isawaitable(coro):
            pyfuncitem.warn(
                pytest.PytestWarning(
                    f"The test {pyfuncitem} is marked with '@pytest.mark.asyncio' "
                    "but it is not an async function. "
                    "Please remove asyncio marker. "
                    "If the test is not marked explicitly, "
                    "check for global markers applied via 'pytestmark'."
                )
            )
            return
        task = asyncio.ensure_future(coro, loop=_loop)
        try:
>           _loop.run_until_complete(task)

/opt/pysetup/.venv/lib/python3.10/site-packages/pytest_asyncio/plugin.py:525: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/local/lib/python3.10/asyncio/base_events.py:625: in run_until_complete
    self._check_running()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

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

    def _check_running(self):
        if self.is_running():
            raise RuntimeError('This event loop is already running')
        if events._get_running_loop() is not None:
>           raise RuntimeError(
                'Cannot run the event loop while another loop is running')
E           RuntimeError: Cannot run the event loop while another loop is running

/usr/local/lib/python3.10/asyncio/base_events.py:586: RuntimeError
======================================================================== short test summary info =========================================================================
FAILED adit/core/tests/utils/test_file_transmit.py::test_start_transmit_file - RuntimeError: Cannot run the event loop while another loop is running
====================================================================== 1 failed, 1 passed in 22.01s ======================================================================
--- Logging error ---
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/logging/__init__.py", line 1103, in emit
    stream.write(msg + self.terminator)
  File "/opt/pysetup/.venv/lib/python3.10/site-packages/colorama/ansitowin32.py", line 47, in write
    self.__convertor.write(text)
  File "/opt/pysetup/.venv/lib/python3.10/site-packages/colorama/ansitowin32.py", line 177, in write
    self.write_and_convert(text)
  File "/opt/pysetup/.venv/lib/python3.10/site-packages/colorama/ansitowin32.py", line 205, in write_and_convert
    self.write_plain_text(text, cursor, len(text))
  File "/opt/pysetup/.venv/lib/python3.10/site-packages/colorama/ansitowin32.py", line 210, in write_plain_text
    self.wrapped.write(text[start:end])
ValueError: I/O operation on closed file.
Call stack:
  File "/usr/local/lib/python3.10/asyncio/base_events.py", line 1784, in call_exception_handler
    self.default_exception_handler(context)
  File "/usr/local/lib/python3.10/asyncio/base_events.py", line 1758, in default_exception_handler
    logger.error('\n'.join(log_lines), exc_info=exc_info)
Message: "Task was destroyed but it is pending!\ntask: <Task pending name='Task-10' coro=<test_start_transmit_file() running at /workspaces/adit/adit/core/tests/utils/test_file_transmit.py:18>>"
Arguments: ()

[medihack]

After some investigation, there is a simple workaround by installing nest_asyncio and then simply put this in the root conftest.py:

def pytest_configure():
    nest_asyncio.apply()

[yuvipanda]

I now see what seems to be official asyncio integration: https://github.com/microsoft/playwright-pytest/tree/main/pytest-playwright-asyncio (and on pypi too). Does that mean we can switch to using that now instead of nest_asyncio?

[martinkirch]

In my experience, yes. That implies updating existing tests to import from playwright.async_api, which also requires adding many async/await and putting all tests in the same loop.