websockets.asyncio.connection.Connection.recv is replacing all RuntimeError exceptions

[lfse-slafleur]

Current implementation of websockets.asyncio.connection.Connection.recv replaces all RuntimeError exceptions removing the relevant stacktrace underneath. Specifically:

        try:
            ...
        except EOFError:
            ...
        except RuntimeError:
            raise RuntimeError(
                "cannot call recv while another coroutine "
                "is already running recv or recv_streaming"
            ) from None  # <-- This replaces another valid RuntimeError

Quick link to the code on version 13.0.1: https://github.com/python-websockets/websockets/blob/13.0.1/src/websockets/asyncio/connection.py#L273

This is an issue as Python asyncio throws most other errors also as a RuntimeError. Specifically, the error that was being covered up in my case was an exception regarding a closed Eventloop.

If there is control over the original exception, perhaps a custom exception is more suitable? Or if there is no control, perhaps we should check the msg in the RuntimeError if it contains a certain string to ensure this code is replacing the proper RuntimeError? I am unsure which case is being covered here with this error.

[aaugustin]

That's a problem, and I should have anticipated it. Let me do something about it.

The best option is to create a new exception type for that case. It should be a subclass of RuntimeError if RuntimeError is part of the public API, and I think it is.

[lfse-slafleur]

@aaugustin Cheers for the quick response! Do you perhaps know what exception is thrown and by which component for the case the current lines of code are trying to replace? It seems that

raise RuntimeError(
                "cannot call recv while another coroutine "
                "is already running recv or recv_streaming"
            ) from None  # <-- This replaces another valid RuntimeError

is replacing some non-descriptive exception and I am curious as to which one.

[aaugustin]

It's replacing this exception.

[lfse-slafleur]

@aaugustin Thank you for fixing this so fast! Good fix.

[aaugustin]

Now available in version 13.1, which I just released.