class ContainerAwareEventDispatcher in Drupal 10

A performance optimized container aware event dispatcher.

This version of the event dispatcher contains the following optimizations in comparison to the Symfony event dispatcher component:

<dl> <dt>Faster instantiation of the event dispatcher service</dt> <dd> Instead of calling <code>addSubscriberService</code> once for each subscriber, a precompiled array of listener definitions is passed directly to the constructor. This is faster by roughly an order of magnitude. The listeners are collected and prepared using a compiler pass. </dd> <dt>Lazy instantiation of listeners</dt> <dd> Services are only retrieved from the container just before invocation. Especially when dispatching the KernelEvents::REQUEST event, this leads to a more timely invocation of the first listener. Overall dispatch runtime is not affected by this change though. </dd> </dl>

Hierarchy

• class \Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher implements \Symfony\Component\EventDispatcher\EventDispatcherInterface

3 files declare their use of ContainerAwareEventDispatcher

ContainerAwareEventDispatcherTest.php in core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php

RedirectResponseSubscriberTest.php in core/tests/Drupal/Tests/Core/EventSubscriber/RedirectResponseSubscriberTest.php

SectionRenderTest.php in core/modules/layout_builder/tests/src/Unit/SectionRenderTest.php

1 string reference to 'ContainerAwareEventDispatcher'

core.services.yml in core/core.services.yml

core/core.services.yml

1 service uses ContainerAwareEventDispatcher

event_dispatcher in core/core.services.yml

Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher

File

core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php, line 33

Namespace

Drupal\Component\EventDispatcher

class ContainerAwareEventDispatcher implements EventDispatcherInterface {

  /**
   * The service container.
   *
   * @var \Symfony\Component\DependencyInjection\ContainerInterface
   */
  protected $container;

  /**
   * Listener definitions.
   *
   * A nested array of listener definitions keyed by event name and priority.
   * A listener definition is an associative array with one of the following key
   * value pairs:
   * - callable: A callable listener
   * - service: An array of the form [service id, method]
   *
   * A service entry will be resolved to a callable only just before its
   * invocation.
   *
   * @var array
   */
  protected $listeners;

  /**
   * Whether listeners need to be sorted prior to dispatch, keyed by event name.
   *
   * @var TRUE[]
   */
  protected $unsorted;

  /**
   * Constructs a container aware event dispatcher.
   *
   * @param \Symfony\Component\DependencyInjection\ContainerInterface $container
   *   The service container.
   * @param array $listeners
   *   A nested array of listener definitions keyed by event name and priority.
   *   The array is expected to be ordered by priority. A listener definition is
   *   an associative array with one of the following key value pairs:
   *   - callable: A callable listener
   *   - service: An array of the form [service id, method]
   *   A service entry will be resolved to a callable only just before its
   *   invocation.
   */
  public function __construct(ContainerInterface $container, array $listeners = []) {
    $this->container = $container;
    $this->listeners = $listeners;
    $this->unsorted = [];
  }

  /**
   * {@inheritdoc}
   */
  public function dispatch(object $event, ?string $eventName = NULL) : object {
    $event_name = $eventName ?? get_class($event);
    if (isset($this->listeners[$event_name])) {

      // Sort listeners if necessary.
      if (isset($this->unsorted[$event_name])) {
        krsort($this->listeners[$event_name]);
        unset($this->unsorted[$event_name]);
      }

      // Invoke listeners and resolve callables if necessary.
      foreach ($this->listeners[$event_name] as &$definitions) {
        foreach ($definitions as &$definition) {
          if (!isset($definition['callable'])) {
            $definition['callable'] = [
              $this->container
                ->get($definition['service'][0]),
              $definition['service'][1],
            ];
          }
          if (is_array($definition['callable']) && isset($definition['callable'][0]) && $definition['callable'][0] instanceof \Closure) {
            $definition['callable'][0] = $definition['callable'][0]();
          }
          call_user_func($definition['callable'], $event, $event_name, $this);
          if ($event
            ->isPropagationStopped()) {
            return $event;
          }
        }
      }
    }
    return $event;
  }

  /**
   * {@inheritdoc}
   */
  public function getListeners($event_name = NULL) : array {
    $result = [];
    if ($event_name === NULL) {

      // If event name was omitted, collect all listeners of all events.
      foreach (array_keys($this->listeners) as $event_name) {
        $listeners = $this
          ->getListeners($event_name);
        if (!empty($listeners)) {
          $result[$event_name] = $listeners;
        }
      }
    }
    elseif (isset($this->listeners[$event_name])) {

      // Sort listeners if necessary.
      if (isset($this->unsorted[$event_name])) {
        krsort($this->listeners[$event_name]);
        unset($this->unsorted[$event_name]);
      }

      // Collect listeners and resolve callables if necessary.
      foreach ($this->listeners[$event_name] as &$definitions) {
        foreach ($definitions as &$definition) {
          if (!isset($definition['callable'])) {
            $definition['callable'] = [
              $this->container
                ->get($definition['service'][0]),
              $definition['service'][1],
            ];
          }
          if (is_array($definition['callable']) && isset($definition['callable'][0]) && $definition['callable'][0] instanceof \Closure) {
            $definition['callable'][0] = $definition['callable'][0]();
          }
          $result[] = $definition['callable'];
        }
      }
    }
    return $result;
  }

  /**
   * {@inheritdoc}
   */
  public function getListenerPriority($event_name, $listener) : ?int {
    if (!isset($this->listeners[$event_name])) {
      return NULL;
    }
    if (is_array($listener) && isset($listener[0]) && $listener[0] instanceof \Closure) {
      $listener[0] = $listener[0]();
    }

    // Resolve service definitions if the listener has not been found so far.
    foreach ($this->listeners[$event_name] as $priority => &$definitions) {
      foreach ($definitions as &$definition) {
        if (!isset($definition['callable'])) {

          // Once the callable is retrieved we keep it for subsequent method
          // invocations on this class.
          $definition['callable'] = [
            $this->container
              ->get($definition['service'][0]),
            $definition['service'][1],
          ];
        }
        if (is_array($definition['callable']) && isset($definition['callable'][0]) && $definition['callable'][0] instanceof \Closure) {
          $definition['callable'][0] = $definition['callable'][0]();
        }
        if ($definition['callable'] === $listener) {
          return $priority;
        }
      }
    }
    return NULL;
  }

  /**
   * {@inheritdoc}
   */
  public function hasListeners($event_name = NULL) : bool {
    if ($event_name !== NULL) {
      return !empty($this->listeners[$event_name]);
    }
    foreach ($this->listeners as $event_listeners) {
      if ($event_listeners) {
        return TRUE;
      }
    }
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function addListener($event_name, $listener, $priority = 0) {
    $this->listeners[$event_name][$priority][] = [
      'callable' => $listener,
    ];
    $this->unsorted[$event_name] = TRUE;
  }

  /**
   * {@inheritdoc}
   */
  public function removeListener($event_name, $listener) {
    if (!isset($this->listeners[$event_name])) {
      return;
    }
    foreach ($this->listeners[$event_name] as $priority => $definitions) {
      foreach ($definitions as $key => $definition) {
        if (!isset($definition['callable'])) {
          if (!$this->container
            ->initialized($definition['service'][0])) {
            continue;
          }
          $definition['callable'] = [
            $this->container
              ->get($definition['service'][0]),
            $definition['service'][1],
          ];
        }
        if (is_array($definition['callable']) && isset($definition['callable'][0]) && $definition['callable'][0] instanceof \Closure && !$listener instanceof \Closure) {
          $definition['callable'][0] = $definition['callable'][0]();
        }
        if (is_array($definition['callable']) && isset($definition['callable'][0]) && !$definition['callable'][0] instanceof \Closure && is_array($listener) && isset($listener[0]) && $listener[0] instanceof \Closure) {
          $listener[0] = $listener[0]();
        }
        if ($definition['callable'] === $listener) {
          unset($definitions[$key]);
        }
      }
      if ($definitions) {
        $this->listeners[$event_name][$priority] = $definitions;
      }
      else {
        unset($this->listeners[$event_name][$priority]);
      }
    }
  }

  /**
   * {@inheritdoc}
   */
  public function addSubscriber(EventSubscriberInterface $subscriber) {
    foreach ($subscriber
      ->getSubscribedEvents() as $event_name => $params) {
      if (is_string($params)) {
        $this
          ->addListener($event_name, [
          $subscriber,
          $params,
        ]);
      }
      elseif (is_string($params[0])) {
        $this
          ->addListener($event_name, [
          $subscriber,
          $params[0],
        ], $params[1] ?? 0);
      }
      else {
        foreach ($params as $listener) {
          $this
            ->addListener($event_name, [
            $subscriber,
            $listener[0],
          ], $listener[1] ?? 0);
        }
      }
    }
  }

  /**
   * {@inheritdoc}
   */
  public function removeSubscriber(EventSubscriberInterface $subscriber) {
    foreach ($subscriber
      ->getSubscribedEvents() as $event_name => $params) {
      if (is_array($params) && is_array($params[0])) {
        foreach ($params as $listener) {
          $this
            ->removeListener($event_name, [
            $subscriber,
            $listener[0],
          ]);
        }
      }
      else {
        $this
          ->removeListener($event_name, [
          $subscriber,
          is_string($params) ? $params : $params[0],
        ]);
      }
    }
  }

}