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IsolatedAsyncioTestCase and asyncio.run no-longer call asyncio.set_event_loop #93896
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import sys import asyncio async def run_subprocess(): proc = await asyncio.create_subprocess_shell( "exit 0", stdin=asyncio.subprocess.DEVNULL, stdout=asyncio.subprocess.DEVNULL, stderr=asyncio.subprocess.DEVNULL, ) await proc.wait() print("success!") async def amain(): await asyncio.to_thread(asyncio.run, run_subprocess()) def main(): asyncio.get_event_loop_policy().set_child_watcher(asyncio.SafeChildWatcher()) asyncio.run(amain()) if __name__ == "__main__": sys.exit(main())
graingert@superjacent ~/projects python3.10 demo_subprocess.py success! graingert@superjacent ~/projects python3.11 demo_subprocess.py Traceback (most recent call last): File "/home/graingert/projects/demo_subprocess.py", line 26, in <module> sys.exit(main()) ^^^^^^ File "/home/graingert/projects/demo_subprocess.py", line 22, in main asyncio.run(amain()) ^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/runners.py", line 181, in run return runner.run(main) ^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/runners.py", line 115, in run return self._loop.run_until_complete(task) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/base_events.py", line 650, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "/home/graingert/projects/demo_subprocess.py", line 17, in amain await asyncio.to_thread(asyncio.run, run_subprocess()) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/threads.py", line 25, in to_thread return await loop.run_in_executor(None, func_call) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/concurrent/futures/thread.py", line 58, in run result = self.fn(*self.args, **self.kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/runners.py", line 181, in run return runner.run(main) ^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/runners.py", line 115, in run return self._loop.run_until_complete(task) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/base_events.py", line 650, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "/home/graingert/projects/demo_subprocess.py", line 6, in run_subprocess proc = await asyncio.create_subprocess_shell( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/subprocess.py", line 205, in create_subprocess_shell transport, protocol = await loop.subprocess_shell( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/base_events.py", line 1647, in subprocess_shell transport = await self._make_subprocess_transport( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/asyncio/unix_events.py", line 204, in _make_subprocess_transport raise RuntimeError("asyncio.get_child_watcher() is not activated, " ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ RuntimeError: asyncio.get_child_watcher() is not activated, subprocess support is not installed.alternatively is there still time to deprecate the child watchers system and the policy system in favor of
asyncio.Runner(loop_factory=asyncio.ProactorEventLoop/asyncio.SelectorEventLoop/uvloop.uvloop.new_event_loop)before the 3.11 release?that would be deprecating:
asyncio.get_event_loop() # already deprecated unless the loop is running asyncio.set_event_loop() # asyncio.set_event_loop(None) should probably be exempt asyncio.get_event_loop_policy() asyncio.set_event_loop_policy() # asyncio.set_event_loop_policy(None) should probably be exempt asyncio.set_child_watcher()asyncio.get_child_watcher()will remain and will always beasyncio.PidfdChildWatcheron old kernels andasyncio.ThreadedChildWatcheron very old kernelsasyncio.new_event_loop()will issue a DeprecationWarning if the current policy is not the default policy, and then become an alias ofif sys.platform == "win32": new_event_loop = ProactorEventLoop else: new_event_loop = SelectorEventLoopthis is also broken with the PidfdChildWatcher
Marking as potential release blocker.
Marking as potential release blocker.
As this is a release blocker can you add @pablogsal as a reviewer for me?
Please, add me as a reviewer to any PR that needs to be merged to address these issues.
https://mail.python.org/archives/list/python-dev@python.org/thread/ORCYBRP432J36LXP32IDX6KLRE7Z646V/
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Go ahead with that PR, Kumar.
I created #94593 which fixes this by reverting to the 3.10 and earlier behavior of setting the event loop if no loop factory was supplied. No new parameter is added so can be backport to 3.11.
- added a commit that references this issue
on Jul 6, 2022 @ixenion Please be civil. This is not the place to get help, but you can find help for Python issues on discuss.python.org.
- locked as off topic and limited conversation to collaborators
on Apr 24, 2024
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in https://github.com/python/cpython/pull/31799/files#diff-1f2ae0f6c6010caf9d5f1c80cd6033a796ffe2b60554f5df84f554f4a08e622b the calls to
asyncio.set_event_loop()were removed which breaks aiohttp aio-libs/aiohttp#6757 andasyncio.SafeChildWatcherthis looks like an intentional breaking change - and if it is should be documented