Always call Hub.OnDisconnectedAsync with an Exception when a client disconnects ungracefully

[halter73]

In some cases (based on reports to the "ASP.NET Discussions" mailing list), Hub.OnDisconnectedAsync can be called without an Exception when SignalR clients disconnect ungracefully.

One way to remove ambiguity between graceful and ungraceful disconnects would be to send a CloseMessage from the SignalR client to the server before it gracefully closes the connection. The absence of a CloseMessage would then be enough for the server to know the client disconnected ungracefully and pass an Exception to Hub.OnDisconnectedAsync.

We already do this in the other direction when the SignalR server closes the connection.

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We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[jkotalik]

Note: make sure to tell all 3rd party clients to adapt if this change is made.

[bradygaster]

cc @chenkennt

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.