Last middleware can invoke next

[jsor]

Allows the last middleware in MiddlewareRunner to invoke $next().

Example

$middleware = new MiddlewareRunner(array(
    function (RequestInterface $request, $next) {
        return $next($request);
    }
));

See eg. https://travis-ci.org/jsor-labs/http/jobs/329394945 for a failing test.

[clue]

Good catch! I think it makes perfect sense to address this 👍

[clue]

Not sure about returning null here as this would break the middleware specification (see README).

It's my understanding that this would be an error, so it should probably throw instead (php.net/manual/en/class.outofrangeexception.php)?

As an alternative, we could also use this to create a "default response", i.e. some kind of response factory and just return a "default response" here?

[jsor]

My understanding is, that it should behave like the middleware just didn't return anything because $next() invoked from the last middleware is just no-op because there is no next.

$middleware = new MiddlewareRunner(array(
    function (RequestInterface $request, $next) {
        // no-op
    }
));

Since the MiddlewareRunner is internal and null will produce an error, i think that this is an acceptable behaviour.

If we throw, we probably should explicitly document, that calling $next() from the last middleware is forbidden or just not pass $next() to the last middleware.

[clue]

[…] there is no next. […] just not pass $next() to the last middleware.

Now that you've said this, I think this actually makes most sense. The last request handler in the chain should not be allowed to call the "next".

[jsor]

If we don't pass $next, then the last middleware callable must have a different signature. I'd rather then pass a $next() which throws.

[clue]

I think you're raising a very good point here. I've just filed #308 to implement this as suggested. Let me know what you think 👍