Preserve exception context in Client.connect

[tvanbaak]

Currently, connection errors give a stack trace like this:

Traceback (most recent call last):
  File "...", line 37, in <module>
    main()
  File "...", line 19, in main
    client.connect(args.url, namespace=args.namespace, transports=["websocket"])
  File ".../socketio/simple_client.py", line 82, in connect
    self.client.connect(url, headers=headers, auth=auth,
  File ".../socketio/client.py", line 159, in connect
    raise exceptions.ConnectionError(exc.args[0]) from None
socketio.exceptions.ConnectionError: Connection error

This discards the stack trace of exc, which can be useful for figuring out what the connection error was. Raising from exc preserves this:

Traceback (most recent call last):
  File ".../engineio/client.py", line 332, in _connect_websocket
    ws = websocket.create_connection(
  File ".../websocket/_core.py", line 646, in create_connection
    websock.connect(url, **options)
  File ".../websocket/_core.py", line 256, in connect
    self.sock, addrs = connect(
  File ".../websocket/_http.py", line 145, in connect
    sock = _open_socket(addrinfo_list, options.sockopt, options.timeout)
  File ".../websocket/_http.py", line 222, in _open_socket
    raise error
  File ".../websocket/_http.py", line 209, in _open_socket
    sock.connect(address)
TimeoutError: timed out

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File ".../socketio/client.py", line 147, in connect
    self.eio.connect(real_url, headers=real_headers,
  File ".../engineio/client.py", line 95, in connect
    return getattr(self, '_connect_' + self.transports[0])(
  File ".../engineio/client.py", line 340, in _connect_websocket
    raise exceptions.ConnectionError('Connection error')
engineio.exceptions.ConnectionError: Connection error

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "...", line 37, in <module>
    main()
  File "...", line 19, in main
    client.connect(args.url, namespace=args.namespace, transports=["websocket"])
  File ".../socketio/simple_client.py", line 82, in connect
    self.client.connect(url, headers=headers, auth=auth,
  File ".../socketio/client.py", line 159, in connect
    raise exceptions.ConnectionError(exc.args[0]) from exc
socketio.exceptions.ConnectionError: Connection error

[miguelgrinberg]

@tvanbaak Could you please make the same change in the async client so that both are consistent? Thanks!

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (6a52e8b) to head (d74c3ef).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1450   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           31        31           
  Lines         2530      2530           
  Branches       432       432           
=========================================
  Hits          2530      2530           

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[miguelgrinberg]

Thanks!