PyPy3.10 test regression: test_remains_alive_post_unhandled_exception fails

[mgorny]

❓ I'm submitting a ...

• 🐞 bug report
• 🐣 feature request
• ❓ question about the decisions made in the repository

🐞 Describe the bug. What is the current behavior?
In cheroot 10.0.1, the tests fails against PyPy3.10 7.3.14, whereas they've passed in 10.0.0. The regressing test is:

         - cheroot/test/test_conn.py:886 test_remains_alive_post_unhandled_exception

❓ What is the motivation / use case for changing the behavior?
Err, making tests pass again?

💡 To Reproduce

Steps to reproduce the behavior:

1. tox -e pypy3 → it will fail immediately because of a bug in typeguard
2. . .tox/pypy3/bin/activate
3. pip uninstall typeguard
4. python -m pytest

💡 Expected behavior
No test regressions.

📋 Details

Traceback

――――――――――――――――――――――――――――――――――――――――――――― test_remains_alive_post_unhandled_exception ―――――――――――――――――――――――――――――――――――――――――――――
[gw5] linux -- Python 3.10.13 /tmp/cheroot/.tox/pypy3/bin/python

mocker = <pytest_mock.plugin.MockerFixture object at 0x00007f14ed6368e0>
monkeypatch = <_pytest.monkeypatch.MonkeyPatch object at 0x00007f14ed636790>
test_client = <cheroot.testing._TestClient object at 0x00007f14ecc5ea30>
testing_server = <cheroot.wsgi.Server object at 0x00007f14ed636b10>
wsgi_server_thread = <Thread(Thread-23 (safe_start), stopped 139727835498176)>

    @pytest.mark.xfail(
        IS_CI and IS_PYPY and IS_PY36 and not IS_SLOW_ENV,
        reason='Fails under PyPy 3.6 under Ubuntu 20.04 in CI for unknown reason',
        # NOTE: Actually covers any Linux
        strict=False,
    )
    def test_remains_alive_post_unhandled_exception(
            mocker,
            monkeypatch,
            test_client,
            testing_server,
            wsgi_server_thread,
    ):
        """Ensure worker threads are resilient to unhandled exceptions."""
    
        class ScaryCrash(BaseException):  # noqa: WPS418, WPS431
            """A simulated crash during HTTP parsing."""
    
        _orig_read_request_line = (
            test_client.server_instance.
            ConnectionClass.RequestHandlerClass.
            read_request_line
        )
    
        def _read_request_line(self):
            _orig_read_request_line(self)
            raise ScaryCrash(666)
    
        monkeypatch.setattr(
            test_client.server_instance.ConnectionClass.RequestHandlerClass,
            'read_request_line',
            _read_request_line,
        )
    
        server_connection_close_spy = mocker.spy(
            test_client.server_instance.ConnectionClass,
            'close',
        )
    
        # NOTE: The initial worker thread count is 10.
        assert len(testing_server.requests._threads) == 10
    
        test_client.get_connection().send(b'GET / HTTP/1.1')
    
        # NOTE: This spy ensure the log entry gets recorded before we're testing
        # NOTE: them and before server shutdown, preserving their order and making
        # NOTE: the log entry presence non-flaky.
        while not server_connection_close_spy.called:  # noqa: WPS328
            pass
    
        # NOTE: This checks for whether there's any crashed threads
        while testing_server.requests.idle < 10:  # noqa: WPS328
            pass
        assert len(testing_server.requests._threads) == 10
        assert all(
            worker_thread.is_alive()
            for worker_thread in testing_server.requests._threads
        )
        testing_server.interrupt = SystemExit('test requesting shutdown')
        assert not testing_server.requests._threads
        wsgi_server_thread.join()  # no extra logs upon server termination
    
        actual_log_entries = testing_server.error_log.calls[:]
        testing_server.error_log.calls.clear()  # prevent post-test assertions
    
        expected_log_entries = (
            (
                logging.ERROR,
                '^Unhandled error while processing an incoming connection '
                r'ScaryCrash\(666,?\)$',
            ),
            (
                logging.INFO,
                '^SystemExit raised: shutting down$',
            ),
        )
    
>       assert len(actual_log_entries) == len(expected_log_entries)
E       assert 1 == 2
E         +1
E         -2

ScaryCrash = <class 'cheroot.test.test_conn.test_remains_alive_post_unhandled_exception.<locals>.ScaryCrash'>
_orig_read_request_line = <function HTTPRequest.read_request_line at 0x00007f14ee11c980>
_read_request_line = <function test_remains_alive_post_unhandled_exception.<locals>._read_request_line at 0x00007f14ed3c0200>
actual_log_entries = [ErrorLogCall(msg='SystemExit raised: shutting down', level=20, traceback='')]
expected_log_entries = ((40, '^Unhandled error while processing an incoming connection ScaryCrash\\(666,?\\)$'), (20, '^SystemExit raised: shutting down$'))
mocker     = <pytest_mock.plugin.MockerFixture object at 0x00007f14ed6368e0>
monkeypatch = <_pytest.monkeypatch.MonkeyPatch object at 0x00007f14ed636790>
server_connection_close_spy = <function close at 0x00007f14ed3c1a60>
test_client = <cheroot.testing._TestClient object at 0x00007f14ecc5ea30>
testing_server = <cheroot.wsgi.Server object at 0x00007f14ed636b10>
wsgi_server_thread = <Thread(Thread-23 (safe_start), stopped 139727835498176)>

cheroot/test/test_conn.py:963: AssertionError

📋 Environment

• Cheroot version: 10.0.1
• CherryPy version: n/a
• Python version: PyPy 3.10 7.3.14
• OS: Gentoo Linux amd64
• Browser: n/a

📋 Additional context
I can reproduce with main (at f156ccd) as well.

[webknjaz]

Oh yeah, I didn't know how to make the test stable under PyPy so I just skipped it in CI on that branch. I think it must be related to PyPy's unpredictable garbage collector.. Thanks for filing this, anyway!

[webknjaz]

I can reproduce with main (at f156ccd) as well.

I just realized that with dropping of the Python 3.6/3.7 in CI, the PyPy versions that were present in CI at the time weren't re-added for newer Python versions. So we'll need to do this and rethink the test structure.

The test itself is new, it didn't exist in 10.0.0 ­— it was initially added to cover the bugfixes that landed in 10.0.1.