Disposal of marhsallable object followed by disposal of jsonRpc on client leads to InvalidOperationException on server

[ni28]

Sometimes I get the following exception on server side on 'await jsonRpc.Completion' when jsonRpc is disposed just after disposal of marshallable object on client side:

  System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
     at System.Collections.Generic.List`1.Enumerator.MoveNext()
     at StreamJsonRpc.Reflection.RpcTargetInfo.DisposeAsync()
     at StreamJsonRpc.JsonRpc.JsonRpcDisconnectedShutdownAsync(JsonRpcDisconnectedEventArgs eventArgs)

I believe the reason is a race condition when accessing the localTargetObjectsToDispose field in the RpcTargetInfo class from different threads. There are other non-concurrent collections in the RpcTargetInfo that probably also need attention.

I created a stress test to reproduce this (attached). It may take a while to get the exception in the server console.

vs-streamjsonrpc-test.zip

[AArnott]

Thank you for your report, investigation and repro! What an awesome bug report.

[AArnott]

@matteo-prosperi I wonder if you could take a first look at this?