DefaultContentSubscriber.php

<?php

declare (strict_types=1);
namespace Drupal\file\EventSubscriber;

use Drupal\Core\DefaultContent\PreExportEvent;
use Drupal\file\FileInterface;
use Psr\Log\LoggerAwareTrait;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * Subscribes to default content-related events.
 *
 * @internal
 *   Event subscribers are internal.
 */
class DefaultContentSubscriber implements EventSubscriberInterface {
  use LoggerAwareTrait;
  
  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() : array {
    return [
      PreExportEvent::class => 'preExport',
    ];
  }
  
  /**
   * Reacts before an entity is exported.
   *
   * @param \Drupal\Core\DefaultContent\PreExportEvent $event
   *   The event object.
   */
  public function preExport(PreExportEvent $event) : void {
    $entity = $event->entity;
    if ($entity instanceof FileInterface) {
      $uri = $entity->getFileUri();
      // Ensure the file has a name (`getFilename()` may return NULL).
      $name = $entity->getFilename() ?? basename($uri);
      $entity->setFilename($name);
      if (file_exists($uri)) {
        $event->metadata
          ->addAttachment($uri, $name);
      }
      else {
        $this->logger?->warning('The file (%uri) associated with file entity %name does not exist.', [
          '%uri' => $uri,
          '%name' => $entity->label(),
        ]);
      }
    }
  }

}