Don't error on LocalProtoclErrors for ws streams

There is a race condition being hit in the autobahn compliance tests
whereby the client closes the stream and the server responds with an
acknowledgement. Whilst the server responds the app sends a message,
which now errors as the WSConnection state is closed.

As the state is managed by the WSStream, rather than the WSConnection
it makes sense to ignore these errors.

Author: pgjones

src/hypercorn/protocol/ws_stream.py

@@ -18,7 +18,7 @@
 from wsproto.extensions import Extension, PerMessageDeflate
 from wsproto.frame_protocol import CloseReason
 from wsproto.handshake import server_extensions_handshake, WEBSOCKET_VERSION
-from wsproto.utilities import generate_accept_token, split_comma_header
+from wsproto.utilities import generate_accept_token, LocalProtocolError, split_comma_header
 
 from .events import Body, Data, EndBody, EndData, Event, Request, Response, StreamClosed
 from ..config import Config
@@ -333,8 +333,12 @@ async def _send_error_response(self, status_code: int) -> None:
         )
 
     async def _send_wsproto_event(self, event: WSProtoEvent) -> None:
-        data = self.connection.send(event)
-        await self.send(Data(stream_id=self.stream_id, data=data))
+        try:
+            data = self.connection.send(event)
+        except LocalProtocolError:
+            pass
+        else:
+            await self.send(Data(stream_id=self.stream_id, data=data))
 
     async def _accept(self, message: WebsocketAcceptEvent) -> None:
         self.state = ASGIWebsocketState.CONNECTED