Add support for all_errors to asyncio.create_connection

[pamelafox]

Feature or enhancement

As a result of the discussion on #74166, @iritkatriel added the all_errors keyword argument to socket.py:create_connection. When set to True, multiple exceptions are raised using an ExceptionGroup instead of a single OSError with the messages combined. I propose adding the same all_errors keyword to asyncio.create_connection, which would raise an ExceptionGroup in the case of connection errors (not for other errors, however).

Pitch

An ExceptionGroup is much nicer to handle than parsing through a concatenated string. An issue in the websockets library indicates that developers would like that for asyncio.create_connection as well. I personally ran into it myself as well.

Example usage:

async def check_ports(host: str, start: int, end: int, max=10):
    for port in range(start, end):
        try:
            future = asyncio.open_connection(host=host, port=port, all_errors=True)
            r, w = await asyncio.wait_for(future, timeout=timeout)
            yield port
            w.close()
        except* ConnectionRefusedError:
            pass
        except* asyncio.TimeoutError:
            pass

Previous discussion

Related discussion on:
#74166

I will send a PR with the proposed change.

[gvanrossum]

Sounds like a useful feature indeed.

[kumaraditya303]

Fixed by #93974