disconnect async handler error: disconnect() takes 0 positional arguments but 1 was given

[mmoollllee]

My problem could relate to #1430 @ Flask-SocketIO, but I can't help myself.

Whenevery my python client disconnects I get this disconnect async handler error:

disconnect async handler error
Traceback (most recent call last):
  File "/home/user/.local/lib/python3.11/site-packages/socketio/async_client.py", line 466, in _trigger_event
    ret = await handler(*args)
                ^^^^^^^^^^^^^^
TypeError: disconnect() takes 0 positional arguments but 1 was given

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/user/.local/lib/python3.11/site-packages/socketio/async_client.py", line 466, in _trigger_event
    ret = await handler(*args)
                ^^^^^^^^^^^^^^
TypeError: disconnect() takes 0 positional arguments but 1 was given

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/user/.local/lib/python3.11/site-packages/engineio/async_client.py", line 472, in _trigger_event
    ret = await self.handlers[event](*args)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.local/lib/python3.11/site-packages/socketio/async_client.py", line 591, in _handle_eio_disconnect
    await self._trigger_event('disconnect', n, reason)
  File "/home/user/.local/lib/python3.11/site-packages/socketio/async_client.py", line 471, in _trigger_event
    ret = await handler(*args[:-1])
          ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/Desktop/app/connection.py", line 67, in disconnect
    sys.exit(0)
SystemExit: 0

I'm on current Debian Bookworm on a RaspberryPi.
My requirements.txt:

python-crontab
picamera2
python-socketio[asyncio_client]
requests
addict
furl
psutil
APScheduler
osm-opening-hours-humanized
suntime
open-gopro
aiohttp

How can I resolve this?

[miguelgrinberg]

Can you please provide the versions of python-socketio, python-engineio and flask-socketio that you are using?

[mmoollllee]

python-engineio==4.11.2
python-socketio==5.12.1
flask-socketio is not installed here.

It seems like this error is related to the sys.exit(0) I had in the disconnect event!

@sio.event
async def disconnect():
   ...
   sys.exit(0)

The error is gone without it.
But why?

[miguelgrinberg]

I missed that on the stack trace, I stopped looking after I read the first part and assumed it was a version mismatch issue, but now it is clear.

The disconnect handler has a legacy no-arguments version, and a current one argument version. The one-arg version is tried first, if that fails, then the no-arg version is called. In this case the one-arg version failed and raised the exception shown in the top part of the stack trace. Python-socketio handles that exception by calling the handler with no arguments. During this second attempt, you raised an exception by calling sys.exit(0). The stack trace shows these chained exceptions, but really the problem is that you are raising SystemExit inside the handler.

Side note, you should consider switching your disconnect handler to the one argument version. This argument is called reason and tells you why the user was disconnected.