'RuntimeError: Event loop is closed' when running under Windows

When running dinghy under windows I’m getting an ‘Event loop is closed’ error from the asyncio lib, even though the output file is created without issues.

The exact same command runs fine under Ubuntu, without exceptions - same repository, github token, dinghy version; error only happens on windows.

• Windows version: Windows 10 20H2 19042.1766, 64b
• Python version: 3.9.1 (64b)
• Dinghy version: 0.12.0

Note: the digest.html file was generated fine, so the exception thrown might be a minor issue related to resource cleanup.

Error log

C:\Users\heckler>python3 -m dinghy https://github.com/heckler/home-assistant-config
Wrote digest: digest.html
Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x00000221711D58B0>
Traceback (most recent call last):
  File "C:\Users\heckler\AppData\Local\Programs\Python\Python39\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "C:\Users\heckler\AppData\Local\Programs\Python\Python39\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "C:\Users\heckler\AppData\Local\Programs\Python\Python39\lib\asyncio\base_events.py", line 746, in call_soon
    self._check_closed()
  File "C:\Users\heckler\AppData\Local\Programs\Python\Python39\lib\asyncio\base_events.py", line 510, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed
Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x00000221711D58B0>
Traceback (most recent call last):
  File "C:\Users\heckler\AppData\Local\Programs\Python\Python39\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "C:\Users\heckler\AppData\Local\Programs\Python\Python39\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "C:\Users\heckler\AppData\Local\Programs\Python\Python39\lib\asyncio\base_events.py", line 746, in call_soon
    self._check_closed()
  File "C:\Users\heckler\AppData\Local\Programs\Python\Python39\lib\asyncio\base_events.py", line 510, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed

[graingert]

you only need to ignore the runtime error rather than switching over to the SelectorEventLoop:

import sys


def unraisablehook(unraisable, /, _old_hook=sys.unraisablehook):
    if unraisable.err_msg == "RuntimeError: Event loop is closed" and isinstance(
        unraisable.object, _ProactorBasePipeTransport
    ):
        return
    return _old_hook(unraisable)

sys.unraisablehook = unraisablehook

(more people should use the ProactorEventLoop!)

[graingert]

@graingert That’s a good comment! 👀

This is dark arts. Is it documented? Might be worth a blog post…

Interesting.

https://vstinner.github.io/sys-unraisablehook-python38.html