Cannot write intercepting middleware

Due to PR #118, it appears we can no longer write middleware that “intercepts” a message from the user (ie: doesn’t call await next())

The easiest example is:

public class Interceptor : IMiddleware, IReceiveActivity
{
    public Task ReceiveActivity(IBotContext context, MiddlewareSet.NextDelegate next) => Task.CompletedTask;
}

because the above Middleware implementation doesn’t call await next(), the hosting Bot’s OnReceive should never be hit; however it will be.

cc @cleemullins @billba @ryanvolum

[cleemullins]

This is fixed by PR #146.

Tests around intercepting middleware have also been added into the test suite. Test showing OnReceive slated to run. Test showing OnReceive running when the Middlware pipeline is empty. Test #1 showing an Intercepting Middleware. Test #2 showing an Intercepting Middlware.

[Stevenic]

@nrobert I haven’t looked at the QnA Maker middleware implementation but i’m assuming it’s currently designed to run on the leading edge of routing which is problematic in general. QnA Maker can be a bit aggressive about answering queries so more often than not you’d want to run it as a fallback if nothing else answers. With our latest middleware design you can do that but it looks like C# is currently missing a key addition that I made to the JS SDK to enable this.

You can code QnA Maker to run on the trailing edge of routing which means it will run after everything else has run but you need a way of knowing if the bot has already replied or not. You could look at the responses queue but that’s not super reliable as it can get flushed (and it’s going away soon) so on the JS side I added a read-only context.responded property you can check to see if any responses have been sent during the turn (it would be a great PR to add that to the C# side.) Using this flag QnA Maker could conditionally decide to run only when nothing else has sent a message.