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tests/test_process.py::TestAsyncio_AIO_Process::test_cancel_post_init fails randomly #709
Description
Found when building on NixOS:
tests/test_process.py .......................................................Unexpected calls to loop.call_exception_handler():
[{'exception': InvalidStateError('invalid state'),
'handle': <Handle _UnixWritePipeTransport._call_connection_lost()>,
'message': 'Exception in callback '
'_UnixWritePipeTransport._call_connection_lost()'},
{'exception': InvalidStateError('invalid state'),
'handle': <Handle _UnixReadPipeTransport._call_connection_lost()>,
'message': 'Exception in callback '
'_UnixReadPipeTransport._call_connection_lost()'},
{'exception': InvalidStateError('invalid state'),
'handle': <Handle BaseSubprocessTransport._call_connection_lost()>,
'message': 'Exception in callback '
'BaseSubprocessTransport._call_connection_lost()'}]
F......................
tests/test_process_spawning.py .
tests/test_regr1.py s
tests/test_runner.py ..
tests/test_signals.py .....................
tests/test_sockets.py ......................s..........
tests/test_tcp.py .......................s.......................................................s.sss.ssss.sss.ss..ssssssss
tests/test_testbase.py ...
tests/test_udp.py ..................ss...
tests/test_unix.py ..............s.s.................
=================================== FAILURES ===================================
________________ TestAsyncio_AIO_Process.test_cancel_post_init _________________
Traceback (most recent call last):
File "/nix/store/48ak878425b9wyrkwd826d2043m3ii36-python3-3.13.11/lib/python3.13/unittest/case.py", line 58, in testPartExecutor
yield
File "/nix/store/48ak878425b9wyrkwd826d2043m3ii36-python3-3.13.11/lib/python3.13/unittest/case.py", line 654, in run
self._callTearDown()
~~~~~~~~~~~~~~~~~~^^
File "/nix/store/48ak878425b9wyrkwd826d2043m3ii36-python3-3.13.11/lib/python3.13/unittest/case.py", line 611, in _callTearDown
self.tearDown()
~~~~~~~~~~~~~^^
File "/nix/store/f10g6ix3rxlnh10aq4yrmyixgnw215lm-python3.13-uvloop-0.22.0/lib/python3.13/site-packages/uvloop/_testbase.py", line 327, in tearDown
super().tearDown()
~~~~~~~~~~~~~~~~^^
File "/nix/store/f10g6ix3rxlnh10aq4yrmyixgnw215lm-python3.13-uvloop-0.22.0/lib/python3.13/site-packages/uvloop/_testbase.py", line 106, in tearDown
self.fail('unexpected calls to loop.call_exception_handler()')
~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/48ak878425b9wyrkwd826d2043m3ii36-python3-3.13.11/lib/python3.13/unittest/case.py", line 732, in fail
raise self.failureException(msg)
AssertionError: unexpected calls to loop.call_exception_handler()
=========================== short test summary info ============================
FAILED tests/test_process.py::TestAsyncio_AIO_Process::test_cancel_post_init - AssertionError: unexpected calls to loop.call_exception_handler()
===== 1 failed, 405 passed, 39 skipped, 8 deselected in 157.00s (0:02:36) ======
Debian maintainers also discussed about this failure: https://www.mail-archive.com/debian-bugs-dist%40lists.debian.org/msg2072110.html
It won't happen every time, but about half the time.
python 3.13.11 or 3.14.2
uvloop 0.22.0
Activity
fantix commented on Jan 11, 2026
Based on the test code and traceback, this is likely a CPython asyncio issue:
Exception in callback _UnixReadPipeTransport._call_connection_lost() handle: <Handle _UnixReadPipeTransport._call_connection_lost()> Traceback (most recent call last): File "asyncio/events.py", line 89, in _run self._context.run(self._callback, *self._args) ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "asyncio/unix_events.py", line 631, in _call_connection_lost self._protocol.connection_lost(exc) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^ File "asyncio/base_subprocess.py", line 305, in connection_lost self.proc._pipe_connection_lost(self.fd, exc) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^ File "asyncio/base_subprocess.py", line 227, in _pipe_connection_lost self._try_finish() ~~~~~~~~~~~~~~~~^^ File "asyncio/base_subprocess.py", line 269, in _try_finish waiter.set_result(self._returncode) ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^ asyncio.exceptions.InvalidStateError: invalid stateImmediately cancelling a subprocess_exec() task in next loop iteration shouldn't cause a InvalidStateError at the very least.
I will verify this, and tentatively disable this AIO test until it's fixed upstream.
fantix commented on Jan 11, 2026
Confirmed that this issue is introduced in python/cpython#140805
fantix commented on Jan 11, 2026
python/cpython#103847 seems to be an issue that is not yet fully fixed, while this test_cancel_post_init test does exist in upstream, let me see why it didn't flake like it is reported here.
fantix commented on Jan 12, 2026
Ahh it's the unhandled exception check thing, it's covering all tests in uvloop, but only some in cpython repo. Let me at least propose for the SubprocessMixin to check unhandled exceptions, and skip this test in uvloop for now.
uvloop 0.23.0