Manually trigger 404 error

Question

I've been struggling to manually trigger dispatch.error from within another controller listener.

The goal is to raise a 404 error where a route parameter is invalid and have it 'caught' by the standard Zend\Mvc\View\Http\RouteNotFoundStrategy so the 404 page is rendered.

public function FooController extends AbstractActionController
{
    protected $foo;

    public function getEventManager()
    {  
        $em = parent::getEventManager();

        // Attach with higher priority than dispatched indexAction
        $em->attach('dispatch', array($this, 'getFooFromRouteParam'), 10);
    }

    public function indexAction()
    {
        $foo = $this->getFoo(); // Error 500 (not 400)
    }

    public function getFooFromRouteParam(EventInterface $event)
    {
        $id = $this->params('id', false);
    
        if (! empty($id)) {

            $foo = $this->aDatabaseService->loadFromTheDatabase($id);

            if ($foo instanceof Foo) {

                $this->setFoo($foo);
                return;
            }
        }

        $response = $event->getResponse();

        $response->setStatusCode(404);
        $event->setError(\Zend\Mvc\Application::ERROR_ROUTER_NO_MATCH);

        $event->getApplication()
              ->getEventManager()
              ->trigger('dispatch.error', $event);

        //return $response;
    }

    public function getObjectFoo()
    {
        if (null == $this->foo) {
            throw new \RuntimeException('foo not set');
        }
        return $this->foo;
    }

    public fucntion setObjectFoo(Foo $object)
    {
        $this->foo = $object;
    }
}

The events are triggered correctly, debugging them gives me :

CALLED Zend\Mvc\View\Http\RouteNotFoundStrategy::detectNotFoundError (The error is : error-controller-not-found)

CALLED Zend\Mvc\View\Http\RouteNotFoundStrategy::prepareNotFoundViewModel CALLED Zend\Mvc\View\Http\RouteNotFoundStrategy::injectNotFoundReason

However, returning the response after gives me a 404 with no body.

return $response; // ends execution with 404 but no body, just white screen.

If I do not return the response the dispatch continues and I get a 500 error

RuntimeException 'foo not set'

How can I manually trigger a 404 error and correctly render the 404 template?

Answer 1

Finally managed to figure out the issue.

The Zend\Mvc\Controller\AbstractController method is expecting a Response to be returned before it will stop execution of the controller's events.

This is the relevant section of the dispatch method.

$result = $this->getEventManager()->trigger(MvcEvent::EVENT_DISPATCH, $e, 
    function ($test) {
        return ($test instanceof Response);
    }
);

if ($result->stopped()) {
    return $result->last();
}

return $e->getResult();

What I needed to do was return my result (which was the error view model) and manually stop event propagation (to ensure that the remaining controller actions were not executed)

// Set the event's 'error' vars
$event->setError(Application::ERROR_EXCEPTION);
$event->setParam('exception', new \Exception('A custom error message here'));

// Trigger the dispatch.error event
$event->getApplication()
      ->getEventManager()
      ->trigger(MvcEvent::EVENT_DISPATCH_ERROR, $event);

// The missing piece! Required to ensure the remaining dispatch 
// listeners are not triggered
$event->stopPropagation(true);

// Contains the view model that was set via the ExceptionStrategy
return $event->getResult();