Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Core\EventSubscriber;
Chris@0: 
Chris@0: use Symfony\Component\EventDispatcher\EventSubscriberInterface;
Chris@0: use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
Chris@0: use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
Chris@0: use Symfony\Component\HttpKernel\KernelEvents;
Chris@0: 
Chris@0: /**
Chris@0:  * Utility base class for exception subscribers.
Chris@0:  *
Chris@0:  * A subscriber may extend this class and implement getHandledFormats() to
Chris@0:  * indicate which request formats it will respond to. Then implement an on*()
Chris@0:  * method for any error code (HTTP response code) that should be handled. For
Chris@0:  * example, to handle a specific error code like 404 Not Found messages add the
Chris@0:  * method:
Chris@0:  *
Chris@0:  * @code
Chris@0:  * public function on404(GetResponseForExceptionEvent $event) {}
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * To implement a fallback for the entire 4xx class of codes, implement the
Chris@0:  * method:
Chris@0:  *
Chris@0:  * @code
Chris@0:  * public function on4xx(GetResponseForExceptionEvent $event) {}
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * That method should then call $event->setResponse() to set the response object
Chris@0:  * for the exception. Alternatively, it may opt not to do so and then other
Chris@0:  * listeners will have the opportunity to handle the exception.
Chris@0:  *
Chris@0:  * Note: Core provides several important exception listeners by default. In most
Chris@0:  * cases, setting the priority of a contrib listener to the default of 0 will
Chris@0:  * do what you expect and handle the exceptions you'd expect it to handle.
Chris@0:  * If a custom priority is set, be aware of the following core-registered
Chris@0:  * listeners.
Chris@0:  *
Chris@0:  * - Fast404ExceptionHtmlSubscriber: 200. This subscriber will return a
Chris@0:  *     minimalist, high-performance 404 page for HTML requests. It is not
Chris@0:  *     recommended to have a priority higher than this one as it will only slow
Chris@0:  *     down that use case.
Chris@0:  * - ExceptionLoggingSubscriber: 50.  This subscriber logs all exceptions but
Chris@0:  *     does not handle them. Do not register a listener with a higher priority
Chris@0:  *     unless you want exceptions to not get logged, which makes debugging more
Chris@0:  *     difficult.
Chris@0:  * - DefaultExceptionSubscriber: -256. The subscriber of last resort, this will
Chris@0:  *     provide generic handling for any exception. A listener with a lower
Chris@0:  *     priority will never get called.
Chris@0:  *
Chris@0:  * All other core-provided exception handlers have negative priorities so most
Chris@0:  * module-provided listeners will naturally take precedence over them.
Chris@0:  */
Chris@0: abstract class HttpExceptionSubscriberBase implements EventSubscriberInterface {
Chris@0: 
Chris@0:   /**
Chris@0:    * Specifies the request formats this subscriber will respond to.
Chris@0:    *
Chris@0:    * @return array
Chris@0:    *   An indexed array of the format machine names that this subscriber will
Chris@0:    *   attempt to process, such as "html" or "json". Returning an empty array
Chris@0:    *   will apply to all formats.
Chris@0:    *
Chris@0:    * @see \Symfony\Component\HttpFoundation\Request
Chris@0:    */
Chris@0:   abstract protected function getHandledFormats();
Chris@0: 
Chris@0:   /**
Chris@0:    * Specifies the priority of all listeners in this class.
Chris@0:    *
Chris@0:    * The default priority is 1, which is very low. To have listeners that have
Chris@0:    * a "first attempt" at handling exceptions return a higher priority.
Chris@0:    *
Chris@0:    * @return int
Chris@0:    *   The event priority of this subscriber.
Chris@0:    */
Chris@0:   protected static function getPriority() {
Chris@0:     return 0;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Handles errors for this subscriber.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent $event
Chris@0:    *   The event to process.
Chris@0:    */
Chris@0:   public function onException(GetResponseForExceptionEvent $event) {
Chris@0:     $exception = $event->getException();
Chris@0: 
Chris@0:     // Make the exception available for example when rendering a block.
Chris@0:     $request = $event->getRequest();
Chris@0:     $request->attributes->set('exception', $exception);
Chris@0: 
Chris@0:     $handled_formats = $this->getHandledFormats();
Chris@0: 
Chris@0:     $format = $request->query->get(MainContentViewSubscriber::WRAPPER_FORMAT, $request->getRequestFormat());
Chris@0: 
Chris@0:     if ($exception instanceof HttpExceptionInterface && (empty($handled_formats) || in_array($format, $handled_formats))) {
Chris@0:       $method = 'on' . $exception->getStatusCode();
Chris@0:       // Keep just the leading number of the status code to produce either a
Chris@0:       // on400 or a 500 method callback.
Chris@0:       $method_fallback = 'on' . substr($exception->getStatusCode(), 0, 1) . 'xx';
Chris@0:       // We want to allow the method to be called and still not set a response
Chris@0:       // if it has additional filtering logic to determine when it will apply.
Chris@0:       // It is therefore the method's responsibility to set the response on the
Chris@0:       // event if appropriate.
Chris@0:       if (method_exists($this, $method)) {
Chris@0:         $this->$method($event);
Chris@0:       }
Chris@0:       elseif (method_exists($this, $method_fallback)) {
Chris@0:         $this->$method_fallback($event);
Chris@0:       }
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Registers the methods in this class that should be listeners.
Chris@0:    *
Chris@0:    * @return array
Chris@0:    *   An array of event listener definitions.
Chris@0:    */
Chris@0:   public static function getSubscribedEvents() {
Chris@0:     $events[KernelEvents::EXCEPTION][] = ['onException', static::getPriority()];
Chris@0:     return $events;
Chris@0:   }
Chris@0: 
Chris@0: }