Handling disconnects

[darabos]

Sorry, I'm not sure it's a bug, but I can't figure out how to handle disconnects.

    | Traceback (most recent call last):
    |   File "python3.11/site-packages/pycrdt_websocket/asgi_server.py", line 33, in send
    |     await self._send(
    |   File "python3.11/site-packages/starlette/_exception_handler.py", line 48, in sender
    |     await send(message)
    |   File "python3.11/site-packages/uvicorn/protocols/websockets/websockets_impl.py", line 358, in asgi_send
    |     raise RuntimeError(msg % message_type)
    | RuntimeError: Unexpected ASGI message 'websocket.send', after sending 'websocket.close' or response already completed.

I'm not following the examples exactly, because I'm using pycrdt in an existing FastAPI application. My code looks basically like this:

router = fastapi.APIRouter()
def ws_exception_handler(exception, log):
    print("exception", exception)
    return True
class WebsocketServer(pycrdt_websocket.WebsocketServer):
    # ... overrides init_room() and get_room() to set up my documents ...
websocket_server = WebsocketServer(
    exception_handler=ws_exception_handler, auto_clean_rooms=False
)
asgi_server = pycrdt_websocket.ASGIServer(websocket_server)

@contextlib.asynccontextmanager
async def lifespan(app):
    async with websocket_server:
        yield

@router.websocket("/ws/crdt/{room_name}")
async def crdt_websocket(websocket: fastapi.WebSocket, room_name: str):
    await asgi_server({"path": room_name}, websocket._receive, websocket._send)

I see asgi_server() has an on_disconnect argument, but what would I do on disconnect? I'm not maintaining a list of websockets.

The whole thing works other than these errors. And I'm only seeing them because of the custom error handler. But I'm seeing hundreds of these exceptions. Sometimes I get variations, like:

| Traceback (most recent call last):
|   File "python3.11/site-packages/uvicorn/protocols/websockets/websockets_impl.py", line 330, in asgi_send
|     await self.send(data)  # type: ignore[arg-type]
|     ^^^^^^^^^^^^^^^^^^^^^
|   File "python3.11/site-packages/websockets/legacy/protocol.py", line 628, in send
|     await self.ensure_open()
|   File "python3.11/site-packages/websockets/legacy/protocol.py", line 938, in ensure_open
|     raise self.connection_closed_exc()
| websockets.exceptions.ConnectionClosedOK: received 1001 (going away); then sent 1001 (going away)
| 
| The above exception was the direct cause of the following exception:
| 
| Traceback (most recent call last):
|   File "python3.11/site-packages/pycrdt_websocket/asgi_server.py", line 33, in send
|     await self._send(
|   File "python3.11/site-packages/starlette/_exception_handler.py", line 48, in sender
|     await send(message)
|   File "python3.11/site-packages/uvicorn/protocols/websockets/websockets_impl.py", line 343, in asgi_send
|     raise ClientDisconnected from exc
| uvicorn.protocols.utils.ClientDisconnected

If this is something that could be fixed in pycrdt, I'm happy to work on it!