With foreverFrame/serverSentEvent/longPolling transport, when an exception is thrown from delayed expression returned from Hub method, no trace for the error in server and no failure callback on client

[Xiaohongt]

Functional impact:
When a client invoking the following hub method, with foreverFrame or serverSentEvent or longPolling transport, on client fail callback not get called (empty 200 response for the Ajax request ), on server no trace logged for the error:

Note, it is not regression.

public IEnumerable<int> GetStuff()
{
    yield return 1;
    yield return 2;
    throw new Exception("This is will repro");
}

Expected:
On client fail callback will get called.
On server trace will log the error.

[halter73]

I totally agree that the client fail callback should get triggered.

However, I think having the server tracing the error would be inconsistent, since we don't normally do that for hub methods that throw synchronously or return a faulted task.

Instead we just bump performance counters when those things happen which we should also do for this.

[abnanda1]

So we should send something in the response to indicate that an error occurred on the server?

[DamianEdwards]

This is incredibly difficult to do as the response is already streaming and there isn't a way to insert a defined error in the middle of a broken stream (in essence). Won't fix.