diff core/lib/Drupal/Core/EventSubscriber/HttpExceptionSubscriberBase.php @ 0:4c8ae668cc8c

Initial import (non-working)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/lib/Drupal/Core/EventSubscriber/HttpExceptionSubscriberBase.php	Wed Nov 29 16:09:58 2017 +0000
@@ -0,0 +1,128 @@
+<?php
+
+namespace Drupal\Core\EventSubscriber;
+
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
+use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
+use Symfony\Component\HttpKernel\KernelEvents;
+
+/**
+ * Utility base class for exception subscribers.
+ *
+ * A subscriber may extend this class and implement getHandledFormats() to
+ * indicate which request formats it will respond to. Then implement an on*()
+ * method for any error code (HTTP response code) that should be handled. For
+ * example, to handle a specific error code like 404 Not Found messages add the
+ * method:
+ *
+ * @code
+ * public function on404(GetResponseForExceptionEvent $event) {}
+ * @endcode
+ *
+ * To implement a fallback for the entire 4xx class of codes, implement the
+ * method:
+ *
+ * @code
+ * public function on4xx(GetResponseForExceptionEvent $event) {}
+ * @endcode
+ *
+ * That method should then call $event->setResponse() to set the response object
+ * for the exception. Alternatively, it may opt not to do so and then other
+ * listeners will have the opportunity to handle the exception.
+ *
+ * Note: Core provides several important exception listeners by default. In most
+ * cases, setting the priority of a contrib listener to the default of 0 will
+ * do what you expect and handle the exceptions you'd expect it to handle.
+ * If a custom priority is set, be aware of the following core-registered
+ * listeners.
+ *
+ * - Fast404ExceptionHtmlSubscriber: 200. This subscriber will return a
+ *     minimalist, high-performance 404 page for HTML requests. It is not
+ *     recommended to have a priority higher than this one as it will only slow
+ *     down that use case.
+ * - ExceptionLoggingSubscriber: 50.  This subscriber logs all exceptions but
+ *     does not handle them. Do not register a listener with a higher priority
+ *     unless you want exceptions to not get logged, which makes debugging more
+ *     difficult.
+ * - DefaultExceptionSubscriber: -256. The subscriber of last resort, this will
+ *     provide generic handling for any exception. A listener with a lower
+ *     priority will never get called.
+ *
+ * All other core-provided exception handlers have negative priorities so most
+ * module-provided listeners will naturally take precedence over them.
+ */
+abstract class HttpExceptionSubscriberBase implements EventSubscriberInterface {
+
+  /**
+   * Specifies the request formats this subscriber will respond to.
+   *
+   * @return array
+   *   An indexed array of the format machine names that this subscriber will
+   *   attempt to process, such as "html" or "json". Returning an empty array
+   *   will apply to all formats.
+   *
+   * @see \Symfony\Component\HttpFoundation\Request
+   */
+  abstract protected function getHandledFormats();
+
+  /**
+   * Specifies the priority of all listeners in this class.
+   *
+   * The default priority is 1, which is very low. To have listeners that have
+   * a "first attempt" at handling exceptions return a higher priority.
+   *
+   * @return int
+   *   The event priority of this subscriber.
+   */
+  protected static function getPriority() {
+    return 0;
+  }
+
+  /**
+   * Handles errors for this subscriber.
+   *
+   * @param \Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent $event
+   *   The event to process.
+   */
+  public function onException(GetResponseForExceptionEvent $event) {
+    $exception = $event->getException();
+
+    // Make the exception available for example when rendering a block.
+    $request = $event->getRequest();
+    $request->attributes->set('exception', $exception);
+
+    $handled_formats = $this->getHandledFormats();
+
+    $format = $request->query->get(MainContentViewSubscriber::WRAPPER_FORMAT, $request->getRequestFormat());
+
+    if ($exception instanceof HttpExceptionInterface && (empty($handled_formats) || in_array($format, $handled_formats))) {
+      $method = 'on' . $exception->getStatusCode();
+      // Keep just the leading number of the status code to produce either a
+      // on400 or a 500 method callback.
+      $method_fallback = 'on' . substr($exception->getStatusCode(), 0, 1) . 'xx';
+      // We want to allow the method to be called and still not set a response
+      // if it has additional filtering logic to determine when it will apply.
+      // It is therefore the method's responsibility to set the response on the
+      // event if appropriate.
+      if (method_exists($this, $method)) {
+        $this->$method($event);
+      }
+      elseif (method_exists($this, $method_fallback)) {
+        $this->$method_fallback($event);
+      }
+    }
+  }
+
+  /**
+   * Registers the methods in this class that should be listeners.
+   *
+   * @return array
+   *   An array of event listener definitions.
+   */
+  public static function getSubscribedEvents() {
+    $events[KernelEvents::EXCEPTION][] = ['onException', static::getPriority()];
+    return $events;
+  }
+
+}