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    <h3>Editing: TraceableEventDispatcher.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\EventDispatcher\Debug;

use Psr\EventDispatcher\StoppableEventInterface;
use Psr\Log\LoggerInterface;
use Symfony\Component\EventDispatcher\EventDispatcherInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\RequestStack;
use Symfony\Component\Stopwatch\Stopwatch;
use Symfony\Contracts\Service\ResetInterface;

/**
 * Collects some data about event listeners.
 *
 * This event dispatcher delegates the dispatching to another one.
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 */
class TraceableEventDispatcher implements EventDispatcherInterface, ResetInterface
{
    protected $logger;
    protected $stopwatch;

    /**
     * @var \SplObjectStorage&lt;WrappedListener, array{string, string}&gt;
     */
    private $callStack;
    private $dispatcher;
    private $wrappedListeners;
    private $orphanedEvents;
    private $requestStack;
    private $currentRequestHash = '';

    public function __construct(EventDispatcherInterface $dispatcher, Stopwatch $stopwatch, ?LoggerInterface $logger = null, ?RequestStack $requestStack = null)
    {
        $this-&gt;dispatcher = $dispatcher;
        $this-&gt;stopwatch = $stopwatch;
        $this-&gt;logger = $logger;
        $this-&gt;wrappedListeners = [];
        $this-&gt;orphanedEvents = [];
        $this-&gt;requestStack = $requestStack;
    }

    /**
     * {@inheritdoc}
     */
    public function addListener(string $eventName, $listener, int $priority = 0)
    {
        $this-&gt;dispatcher-&gt;addListener($eventName, $listener, $priority);
    }

    /**
     * {@inheritdoc}
     */
    public function addSubscriber(EventSubscriberInterface $subscriber)
    {
        $this-&gt;dispatcher-&gt;addSubscriber($subscriber);
    }

    /**
     * {@inheritdoc}
     */
    public function removeListener(string $eventName, $listener)
    {
        if (isset($this-&gt;wrappedListeners[$eventName])) {
            foreach ($this-&gt;wrappedListeners[$eventName] as $index =&gt; $wrappedListener) {
                if ($wrappedListener-&gt;getWrappedListener() === $listener || ($listener instanceof \Closure &amp;&amp; $wrappedListener-&gt;getWrappedListener() == $listener)) {
                    $listener = $wrappedListener;
                    unset($this-&gt;wrappedListeners[$eventName][$index]);
                    break;
                }
            }
        }

        return $this-&gt;dispatcher-&gt;removeListener($eventName, $listener);
    }

    /**
     * {@inheritdoc}
     */
    public function removeSubscriber(EventSubscriberInterface $subscriber)
    {
        return $this-&gt;dispatcher-&gt;removeSubscriber($subscriber);
    }

    /**
     * {@inheritdoc}
     */
    public function getListeners(?string $eventName = null)
    {
        return $this-&gt;dispatcher-&gt;getListeners($eventName);
    }

    /**
     * {@inheritdoc}
     */
    public function getListenerPriority(string $eventName, $listener)
    {
        // we might have wrapped listeners for the event (if called while dispatching)
        // in that case get the priority by wrapper
        if (isset($this-&gt;wrappedListeners[$eventName])) {
            foreach ($this-&gt;wrappedListeners[$eventName] as $wrappedListener) {
                if ($wrappedListener-&gt;getWrappedListener() === $listener || ($listener instanceof \Closure &amp;&amp; $wrappedListener-&gt;getWrappedListener() == $listener)) {
                    return $this-&gt;dispatcher-&gt;getListenerPriority($eventName, $wrappedListener);
                }
            }
        }

        return $this-&gt;dispatcher-&gt;getListenerPriority($eventName, $listener);
    }

    /**
     * {@inheritdoc}
     */
    public function hasListeners(?string $eventName = null)
    {
        return $this-&gt;dispatcher-&gt;hasListeners($eventName);
    }

    /**
     * {@inheritdoc}
     */
    public function dispatch(object $event, ?string $eventName = null): object
    {
        $eventName = $eventName ?? \get_class($event);

        if (null === $this-&gt;callStack) {
            $this-&gt;callStack = new \SplObjectStorage();
        }

        $currentRequestHash = $this-&gt;currentRequestHash = $this-&gt;requestStack &amp;&amp; ($request = $this-&gt;requestStack-&gt;getCurrentRequest()) ? spl_object_hash($request) : '';

        if (null !== $this-&gt;logger &amp;&amp; $event instanceof StoppableEventInterface &amp;&amp; $event-&gt;isPropagationStopped()) {
            $this-&gt;logger-&gt;debug(sprintf('The &quot;%s&quot; event is already stopped. No listeners have been called.', $eventName));
        }

        $this-&gt;preProcess($eventName);
        try {
            $this-&gt;beforeDispatch($eventName, $event);
            try {
                $e = $this-&gt;stopwatch-&gt;start($eventName, 'section');
                try {
                    $this-&gt;dispatcher-&gt;dispatch($event, $eventName);
                } finally {
                    if ($e-&gt;isStarted()) {
                        $e-&gt;stop();
                    }
                }
            } finally {
                $this-&gt;afterDispatch($eventName, $event);
            }
        } finally {
            $this-&gt;currentRequestHash = $currentRequestHash;
            $this-&gt;postProcess($eventName);
        }

        return $event;
    }

    /**
     * @return array
     */
    public function getCalledListeners(?Request $request = null)
    {
        if (null === $this-&gt;callStack) {
            return [];
        }

        $hash = $request ? spl_object_hash($request) : null;
        $called = [];
        foreach ($this-&gt;callStack as $listener) {
            [$eventName, $requestHash] = $this-&gt;callStack-&gt;getInfo();
            if (null === $hash || $hash === $requestHash) {
                $called[] = $listener-&gt;getInfo($eventName);
            }
        }

        return $called;
    }

    /**
     * @return array
     */
    public function getNotCalledListeners(?Request $request = null)
    {
        try {
            $allListeners = $this-&gt;getListeners();
        } catch (\Exception $e) {
            if (null !== $this-&gt;logger) {
                $this-&gt;logger-&gt;info('An exception was thrown while getting the uncalled listeners.', ['exception' =&gt; $e]);
            }

            // unable to retrieve the uncalled listeners
            return [];
        }

        $hash = $request ? spl_object_hash($request) : null;
        $calledListeners = [];

        if (null !== $this-&gt;callStack) {
            foreach ($this-&gt;callStack as $calledListener) {
                [, $requestHash] = $this-&gt;callStack-&gt;getInfo();

                if (null === $hash || $hash === $requestHash) {
                    $calledListeners[] = $calledListener-&gt;getWrappedListener();
                }
            }
        }

        $notCalled = [];
        foreach ($allListeners as $eventName =&gt; $listeners) {
            foreach ($listeners as $listener) {
                if (!\in_array($listener, $calledListeners, true)) {
                    if (!$listener instanceof WrappedListener) {
                        $listener = new WrappedListener($listener, null, $this-&gt;stopwatch, $this);
                    }
                    $notCalled[] = $listener-&gt;getInfo($eventName);
                }
            }
        }

        uasort($notCalled, [$this, 'sortNotCalledListeners']);

        return $notCalled;
    }

    public function getOrphanedEvents(?Request $request = null): array
    {
        if ($request) {
            return $this-&gt;orphanedEvents[spl_object_hash($request)] ?? [];
        }

        if (!$this-&gt;orphanedEvents) {
            return [];
        }

        return array_merge(...array_values($this-&gt;orphanedEvents));
    }

    public function reset()
    {
        $this-&gt;callStack = null;
        $this-&gt;orphanedEvents = [];
        $this-&gt;currentRequestHash = '';
    }

    /**
     * Proxies all method calls to the original event dispatcher.
     *
     * @param string $method    The method name
     * @param array  $arguments The method arguments
     *
     * @return mixed
     */
    public function __call(string $method, array $arguments)
    {
        return $this-&gt;dispatcher-&gt;{$method}(...$arguments);
    }

    /**
     * Called before dispatching the event.
     */
    protected function beforeDispatch(string $eventName, object $event)
    {
    }

    /**
     * Called after dispatching the event.
     */
    protected function afterDispatch(string $eventName, object $event)
    {
    }

    private function preProcess(string $eventName): void
    {
        if (!$this-&gt;dispatcher-&gt;hasListeners($eventName)) {
            $this-&gt;orphanedEvents[$this-&gt;currentRequestHash][] = $eventName;

            return;
        }

        foreach ($this-&gt;dispatcher-&gt;getListeners($eventName) as $listener) {
            $priority = $this-&gt;getListenerPriority($eventName, $listener);
            $wrappedListener = new WrappedListener($listener instanceof WrappedListener ? $listener-&gt;getWrappedListener() : $listener, null, $this-&gt;stopwatch, $this);
            $this-&gt;wrappedListeners[$eventName][] = $wrappedListener;
            $this-&gt;dispatcher-&gt;removeListener($eventName, $listener);
            $this-&gt;dispatcher-&gt;addListener($eventName, $wrappedListener, $priority);
            $this-&gt;callStack-&gt;attach($wrappedListener, [$eventName, $this-&gt;currentRequestHash]);
        }
    }

    private function postProcess(string $eventName): void
    {
        unset($this-&gt;wrappedListeners[$eventName]);
        $skipped = false;
        foreach ($this-&gt;dispatcher-&gt;getListeners($eventName) as $listener) {
            if (!$listener instanceof WrappedListener) { // #12845: a new listener was added during dispatch.
                continue;
            }
            // Unwrap listener
            $priority = $this-&gt;getListenerPriority($eventName, $listener);
            $this-&gt;dispatcher-&gt;removeListener($eventName, $listener);
            $this-&gt;dispatcher-&gt;addListener($eventName, $listener-&gt;getWrappedListener(), $priority);

            if (null !== $this-&gt;logger) {
                $context = ['event' =&gt; $eventName, 'listener' =&gt; $listener-&gt;getPretty()];
            }

            if ($listener-&gt;wasCalled()) {
                if (null !== $this-&gt;logger) {
                    $this-&gt;logger-&gt;debug('Notified event &quot;{event}&quot; to listener &quot;{listener}&quot;.', $context);
                }
            } else {
                $this-&gt;callStack-&gt;detach($listener);
            }

            if (null !== $this-&gt;logger &amp;&amp; $skipped) {
                $this-&gt;logger-&gt;debug('Listener &quot;{listener}&quot; was not called for event &quot;{event}&quot;.', $context);
            }

            if ($listener-&gt;stoppedPropagation()) {
                if (null !== $this-&gt;logger) {
                    $this-&gt;logger-&gt;debug('Listener &quot;{listener}&quot; stopped propagation of the event &quot;{event}&quot;.', $context);
                }

                $skipped = true;
            }
        }
    }

    private function sortNotCalledListeners(array $a, array $b)
    {
        if (0 !== $cmp = strcmp($a['event'], $b['event'])) {
            return $cmp;
        }

        if (\is_int($a['priority']) &amp;&amp; !\is_int($b['priority'])) {
            return 1;
        }

        if (!\is_int($a['priority']) &amp;&amp; \is_int($b['priority'])) {
            return -1;
        }

        if ($a['priority'] === $b['priority']) {
            return 0;
        }

        if ($a['priority'] &gt; $b['priority']) {
            return -1;
        }

        return 1;
    }
}
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