asyncio.exceptions.CancelledError with simple async code

[Almenon]

The simplified version of the hello world example from https://docs.python.org/3/library/asyncio.html:

import asyncio


async def main():
    pass

asyncio.run(main())

results in a error being logged to stderr:

Error on reading from the event loop self pipe
loop: <ProactorEventLoop running=True closed=False debug=False>
Traceback (most recent call last):
  File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\proactor_events.py", line 768, in _loop_self_reading
    f.result()  # may raise
asyncio.exceptions.CancelledError
Error on reading from the event loop self pipe
loop: <ProactorEventLoop running=True closed=False debug=False>
Traceback (most recent call last):
  File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\proactor_events.py", line 768, in _loop_self_reading
    f.result()  # may raise
asyncio.exceptions.CancelledError

(Note that it logs to stderr instead of throwing an exception because that's the default behavior of event loops - see default_exception_handler of C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\base_events.py.)

Exepcted results:
No error logged, same as when program is run via python directly

Actual Results:
Error logged.

OS: Windows 10
Python: v3.9

Full error: (logged if you specify debug=True)

``` Error on reading from the event loop self pipe handle_traceback: Handle created at (most recent call last): File "c:\Users\almenon\.vscode\extensions\almenon.arepl-2.0.2\node_modules\arepl-backend\python\arepl_python_evaluator.py", line 330, in main(input()) File "c:\Users\almenon\.vscode\extensions\almenon.arepl-2.0.2\node_modules\arepl-backend\python\arepl_python_evaluator.py", line 298, in main return_info = exec_input(execArgs) File "c:\Users\almenon\.vscode\extensions\almenon.arepl-2.0.2\node_modules\arepl-backend\python\arepl_python_evaluator.py", line 242, in exec_input run_context.run(exec, exec_args.evalCode, eval_locals) File "", line 7, in File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\runners.py", line 44, in run return loop.run_until_complete(main) File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\base_events.py", line 629, in run_until_complete self.run_forever() File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\windows_events.py", line 320, in run_forever self._self_reading_future.cancel() File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\windows_events.py", line 80, in cancel return super().cancel(msg=msg) loop: Traceback (most recent call last): File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\proactor_events.py", line 768, in _loop_self_reading f.result() # may raise asyncio.exceptions.CancelledError Error on reading from the event loop self pipe handle_traceback: Handle created at (most recent call last): File "c:\Users\almenon\.vscode\extensions\almenon.arepl-2.0.2\node_modules\arepl-backend\python\arepl_python_evaluator.py", line 330, in main(input()) File "c:\Users\almenon\.vscode\extensions\almenon.arepl-2.0.2\node_modules\arepl-backend\python\arepl_python_evaluator.py", line 298, in main return_info = exec_input(execArgs) File "c:\Users\almenon\.vscode\extensions\almenon.arepl-2.0.2\node_modules\arepl-backend\python\arepl_python_evaluator.py", line 242, in exec_input run_context.run(exec, exec_args.evalCode, eval_locals) File "", line 7, in File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\runners.py", line 48, in run loop.run_until_complete(loop.shutdown_asyncgens()) File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\base_events.py", line 629, in run_until_complete self.run_forever() File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\windows_events.py", line 320, in run_forever self._self_reading_future.cancel() File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\windows_events.py", line 80, in cancel return super().cancel(msg=msg) loop: Traceback (most recent call last): File "C:\Users\almenon\AppData\Local\Programs\Python\Python39\lib\asyncio\proactor_events.py", line 768, in _loop_self_reading f.result() # may raise asyncio.exceptions.CancelledError ```

[Almenon]

So basically the event loop is getting cancelled for some reason... but I'm not sure why.

I tried doing a simple exec but that didn't get the error. I should try running arepl directly, mocking the JSON input, and changing code around untill I figure out what causes it.