0.25.1 regression Python 3.9 asyncio_mode="auto" # RuntimeError: There is no current event loop in thread 'MainThread'

[dimaqq]

Happy new year.

0.25.1 was released recently and somehow it fails on Python 3.9 specifically.

In my case, asyncio_mode = "auto" is used, so maybe similar to #658, however I don't know if that's required for the regression.

Meanwhile, Python 3.8 is OK (0.25.x can't be used, 0.24 is used instead)
And Python 3.10, 3.11, 3.12, 3.13 are OK (with the new version)

Version resolution:

    { name = "pytest-asyncio", version = "0.24.0", source = { registry = "https://pypi.org/simple" }, marker = "python_full_version < '3.9'" },
    { name = "pytest-asyncio", version = "0.25.1", source = { registry = "https://pypi.org/simple" }, marker = "python_full_version >= '3.9'" },

Run log: https://github.com/juju/python-libjuju/actions/runs/12423507633

Screenshot for the above:

I've manually validated that 0.25.0 works fine in my setup.

[dimaqq]

Log, if helps any:

self = <tests.unit.test_model.TestModelState testMethod=test_apply_delta>

    def test_apply_delta(self):
>       model = Model()

tests/unit/test_model.py:72:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
juju/model/__init__.py:677: in __init__
    self._watch_stopping = asyncio.Event()
/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/lib/python3.9/asyncio/locks.py:177: in __init__
    self._loop = events.get_event_loop()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <asyncio.unix_events._UnixDefaultEventLoopPolicy object at 0x105a521f0>

    def get_event_loop(self):
        """Get the event loop for the current context.

        Returns an instance of EventLoop or raises an exception.
        """
        if (self._local._loop is None and
                not self._local._set_called and
                threading.current_thread() is threading.main_thread()):
            self.set_event_loop(self.new_event_loop())

        if self._local._loop is None:
>           raise RuntimeError('There is no current event loop in thread %r.'
                               % threading.current_thread().name)
E           RuntimeError: There is no current event loop in thread 'MainThread'.

[dimaqq]

My config, since the most likely cause is the change that fixed interleaved loop scopes:

[tool.pytest.ini_options]
addopts = "-ra -v"
asyncio_default_fixture_loop_scope = "function"
asyncio_mode = "auto"
filterwarnings = "ignore::DeprecationWarning:websockets"
markers = [
    "serial: mark a test that must run by itself",
    "wait_for_idle: mark a test that waits for the model to be idle",
    "bundle: mark a test that uses a bundle",
]

I don't have custom loop_scope's in the tests, only this config.

I do, however, have a mix of modern pytest tests (module-level test_foo(): ...) and older class-based tests class TestFoo(unittest.TestCase): def test_foo(self): ...)

Easy reproducer:

git clone [email protected]:juju/python-libjuju.git
cd python-libjuju
# currently at a58645e
uvx -p 3.9 tox -e unit

[seifertm]

Thanks for the detailed report!
The failing test is a synchronous test. Maybe #1029 introduced a regression here.