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    <h3>Editing: Mailer.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\Mailer;

use Psr\EventDispatcher\EventDispatcherInterface;
use Symfony\Component\Mailer\Event\MessageEvent;
use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
use Symfony\Component\Mailer\Messenger\SendEmailMessage;
use Symfony\Component\Mailer\Transport\TransportInterface;
use Symfony\Component\Messenger\Exception\HandlerFailedException;
use Symfony\Component\Messenger\MessageBusInterface;
use Symfony\Component\Mime\RawMessage;

/**
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 */
final class Mailer implements MailerInterface
{
    private TransportInterface $transport;
    private ?MessageBusInterface $bus;
    private ?EventDispatcherInterface $dispatcher;

    public function __construct(TransportInterface $transport, MessageBusInterface $bus = null, EventDispatcherInterface $dispatcher = null)
    {
        $this-&gt;transport = $transport;
        $this-&gt;bus = $bus;
        $this-&gt;dispatcher = $dispatcher;
    }

    public function send(RawMessage $message, Envelope $envelope = null): void
    {
        if (null === $this-&gt;bus) {
            $this-&gt;transport-&gt;send($message, $envelope);

            return;
        }

        $stamps = [];
        if (null !== $this-&gt;dispatcher) {
            // The dispatched event here has `queued` set to `true`; the goal is NOT to render the message, but to let
            // listeners do something before a message is sent to the queue.
            // We are using a cloned message as we still want to dispatch the **original** message, not the one modified by listeners.
            // That's because the listeners will run again when the email is sent via Messenger by the transport (see `AbstractTransport`).
            // Listeners should act depending on the `$queued` argument of the `MessageEvent` instance.
            $clonedMessage = clone $message;
            $clonedEnvelope = null !== $envelope ? clone $envelope : Envelope::create($clonedMessage);
            $event = new MessageEvent($clonedMessage, $clonedEnvelope, (string) $this-&gt;transport, true);
            $this-&gt;dispatcher-&gt;dispatch($event);
            $stamps = $event-&gt;getStamps();
        }

        try {
            $this-&gt;bus-&gt;dispatch(new SendEmailMessage($message, $envelope), $stamps);
        } catch (HandlerFailedException $e) {
            foreach ($e-&gt;getNestedExceptions() as $nested) {
                if ($nested instanceof TransportExceptionInterface) {
                    throw $nested;
                }
            }
            throw $e;
        }
    }
}
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