WebSocketDisconnectEvent is not handling the reason field

[frankie567]

While investigating an issue with HTTPX WS, I noticed that, when a client disconnects, Uvicorn handles the code but not the reason:

uvicorn/uvicorn/protocols/websockets/wsproto_impl.py

Line 214 in a2219eb

self.queue.put_nowait({"type": "websocket.disconnect", "code": event.code})

uvicorn/uvicorn/protocols/websockets/websockets_impl.py

Line 384 in a2219eb

return {"type": "websocket.disconnect", "code": exc.code}

After having a look at the ASGI specification, it seems indeed that the Disconnect (receive) event does not support this field: https://asgi.readthedocs.io/en/latest/specs/www.html#disconnect-receive-event-ws

However, from Starlette, the WebSocketDisconnect class does have a field intended for reason, but probably never used (at least when running behind Uvicorn):

https://github.com/encode/starlette/blob/4e453ce91940cc7c995e6c728e3fdf341c039056/starlette/websockets.py#L19-L22

---

So, I'm not sure where the problem comes from:

1. Is it an issue from the ASGI spec itself? The reason field should probably a thing in the Disconnect (receive) event
2. Should we remove the reason field from the Starlette's WebSocketDisconnect exception?
3. Should Uvicorn diverge a bit from the ASGI spec to set this reason field?

Insights about this would be welcome :)

[frankie567]

Asked the question asgiref's side: django/asgiref#459