FinalMissingContentSubscriber.php

<?php

namespace Drupal\Core\Config\Importer;

use Drupal\Core\Config\ConfigEvents;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * Final event subscriber to the missing content event.
 *
 * Ensure that all missing content dependencies are removed from the event so
 * the importer can complete.
 *
 * @see \Drupal\Core\Config\ConfigImporter::processMissingContent()
 */
class FinalMissingContentSubscriber implements EventSubscriberInterface {
    
    /**
     * Handles the missing content event.
     *
     * @param \Drupal\Core\Config\Importer\MissingContentEvent $event
     *   The missing content event.
     */
    public function onMissingContent(MissingContentEvent $event) {
        foreach (array_keys($event->getMissingContent()) as $uuid) {
            $event->resolveMissingContent($uuid);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() {
        // This should always be the final event as it will mark all content
        // dependencies as resolved.
        $events[ConfigEvents::IMPORT_MISSING_CONTENT][] = [
            'onMissingContent',
            -1024,
        ];
        return $events;
    }

}