Add exception handler pipeline behavior

I think there’s a place for an IRequestExceptionHandler in the vein of IPreRequestProcessor and IPostRequestProcessor.

It would have a single method to implement

Task Handle(
    TRequest request,
    Exception exception,
    ExceptionHandlerState<TResponse> state,
    CancellationToken cancellationToken
)

The state object would work like this

    public class RequestExceptionHandlerState<TResponse>
    {
        public TResponse Response { get; private set; }

        public bool Handled { get; private set; }

        public void SetHandled(TResponse response = default)
        {
            Handled = true;
            Response = response;
        }
    }

Here’s my use case for it. I have certain requests that update a database using Entity Framework Core. One project has the implementation in a request handler with no specific DB provider dependency/reference. I have another layer that implements the specific DB provider and naming. The exception is thrown as a type from the DB provider library. With a IRequestExceptionHandler, I can intercept the exception, do some DB specific logic and throw a domain specific exception.

Thoughts?

P.S.

I thought if this is in the main library, I could do some work to resolve IRequestExceptionHandlers based on the type of the exception similar to how catch blocks work, but I would need the ServiceFactory.

[jbogard]

Fixed by #339

[developermj]

Is there any traction on getting this exception handling code released? I’d like to make a handler that sends the exception to application insights.