Handle sending trailer for completion when web socket closed

[gavar]

GrpcWebSocketBridgeHandler throws an exception when trying to send an empty trailer for completion.

Checking state of the underlying web socket instance before sending an empty trailer does not help, so using a try / catch block instead.

Only WebSocketError.InvalidState is handled so should not affect any other functionality.

The error looks like following

WebSocketException: The WebSocket is in an invalid state ('Aborted') for this operation. Valid states are: 'Open, CloseReceived'
System.Net.WebSockets.WebSocketValidate.ThrowIfInvalidState (System.Net.WebSockets.WebSocketState currentState, System.Boolean isDisposed, System.Net.WebSockets.WebSocketState[] validStates) (at <6bb3336e864c4ab48c43a2538573e586>:0)
System.Net.WebSockets.ManagedWebSocket.SendPrivateAsync (System.ReadOnlyMemory`1[T] buffer, System.Net.WebSockets.WebSocketMessageType messageType, System.Boolean endOfMessage, System.Threading.CancellationToken cancellationToken) (at <6bb3336e864c4ab48c43a2538573e586>:0)
--- End of stack trace from previous location where exception was thrown ---
GrpcWebSocketBridge.Client.WebSockets.SystemNetWebSocketsClientWebSocket.SendAsync (System.ArraySegment`1[T] buffer, System.Net.WebSockets.WebSocketMessageType messageType, System.Boolean endOfMessage, System.Threading.CancellationToken cancellationToken) (at ./Library/PackageCache/com.cysharp.grpcwebsocketbridge@43c5556d52/GrpcWebSocketBridge.Client/WebSockets/SystemNetWebSocketsClientWebSocket.cs:40)
Cysharp.Threading.Tasks.UniTask+ExceptionResultSource.GetResult (System.Int16 token) (at ./Library/PackageCache/com.cysharp.unitask@50a67d8f41/Runtime/UniTask.Factory.cs:205)
Cysharp.Threading.Tasks.UniTask+Awaiter.GetResult () (at ./Library/PackageCache/com.cysharp.unitask@50a67d8f41/Runtime/UniTask.cs:312)
GrpcWebSocketBridge.Client.GrpcWebSocketBridgeHandler.ProcessRequestAsync (GrpcWebSocketBridge.Client.WebSockets.IClientWebSocket clientWebSocket, System.Net.Http.HttpRequestMessage request, GrpcWebSocketBridge.Client.Internal.ConnectionContext ctx, System.Threading.CancellationToken cancellationToken) (at ./Library/PackageCache/com.cysharp.grpcwebsocketbridge@43c5556d52/GrpcWebSocketBridge.Client/GrpcWebSocketBridgeHandler.cs:187)
GrpcWebSocketBridge.Client.GrpcWebSocketBridgeHandler.ProcessRequestAsync (GrpcWebSocketBridge.Client.WebSockets.IClientWebSocket clientWebSocket, System.Net.Http.HttpRequestMessage request, GrpcWebSocketBridge.Client.Internal.ConnectionContext ctx, System.Threading.CancellationToken cancellationToken) (at ./Library/PackageCache/com.cysharp.grpcwebsocketbridge@43c5556d52/GrpcWebSocketBridge.Client/GrpcWebSocketBridgeHandler.cs:196)
UnityEngine.Debug:LogException(Exception)
Cysharp.Threading.Tasks.UniTaskScheduler:PublishUnobservedTaskException(Exception) (at ./Library/PackageCache/com.cysharp.unitask@50a67d8f41/Runtime/UniTaskScheduler.cs:90)
Cysharp.Threading.Tasks.ExceptionHolder:Finalize() (at ./Library/PackageCache/com.cysharp.unitask@50a67d8f41/Runtime/UniTaskCompletionSource.cs:66)

[gavar]

Hi @mayuki !

Here's a minor fix of the GrpcWebSocketBridgeHandler, please take a look whenever you've got a minute.

[mayuki]

Thanks! It looks good to me.