NodeTranslationExceptionSubscriber.php

<?php

namespace Drupal\node\EventSubscriber;

use Drupal\Core\KeyValueStore\KeyValueFactoryInterface;
use Drupal\Core\Language\LanguageManagerInterface;
use Drupal\Core\ParamConverter\ParamNotConvertedException;
use Drupal\Core\Routing\UrlGeneratorInterface;
use Drupal\Core\State\StateInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpKernel\Event\ExceptionEvent;
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
use Symfony\Component\HttpKernel\KernelEvents;

/**
 * Redirect node translations that have been consolidated by migration.
 *
 * If we migrated node translations from Drupal 6 or 7, these nodes are now
 * combined with their source language node. Since there still might be
 * references to the URLs of these now consolidated nodes, this service catches
 * the 404s and try to redirect them to the right node in the right language.
 *
 * The mapping of the old nids to the new ones is made by the
 * NodeTranslationMigrateSubscriber class during the migration and is stored
 * in the "node_translation_redirect" key/value collection.
 *
 * @see \Drupal\node\NodeServiceProvider
 * @see \Drupal\node\EventSubscriber\NodeTranslationMigrateSubscriber
 */
class NodeTranslationExceptionSubscriber implements EventSubscriberInterface {
    
    /**
     * The key value factory.
     *
     * @var \Drupal\Core\KeyValueStore\KeyValueFactoryInterface
     */
    protected $keyValue;
    
    /**
     * The language manager.
     *
     * @var \Drupal\Core\Language\LanguageManagerInterface
     */
    protected $languageManager;
    
    /**
     * The URL generator.
     *
     * @var \Drupal\Core\Routing\UrlGeneratorInterface
     */
    protected $urlGenerator;
    
    /**
     * The state service.
     *
     * @var \Drupal\Core\State\StateInterface
     */
    protected $state;
    
    /**
     * Constructs the NodeTranslationExceptionSubscriber.
     *
     * @param \Drupal\Core\KeyValueStore\KeyValueFactoryInterface $key_value
     *   The key value factory.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     * @param \Drupal\Core\Routing\UrlGeneratorInterface $url_generator
     *   The URL generator.
     * @param \Drupal\Core\State\StateInterface $state
     *   The state service.
     */
    public function __construct(KeyValueFactoryInterface $key_value, LanguageManagerInterface $language_manager, UrlGeneratorInterface $url_generator, StateInterface $state) {
        $this->keyValue = $key_value;
        $this->languageManager = $language_manager;
        $this->urlGenerator = $url_generator;
        $this->state = $state;
    }
    
    /**
     * Redirects not found node translations using the key value collection.
     *
     * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $event
     *   The exception event.
     */
    public function onException(ExceptionEvent $event) {
        $exception = $event->getThrowable();
        // If this is not a 404, we don't need to check for a redirection.
        if (!$exception instanceof NotFoundHttpException) {
            return;
        }
        $previous_exception = $exception->getPrevious();
        if ($previous_exception instanceof ParamNotConvertedException) {
            $route_name = $previous_exception->getRouteName();
            $parameters = $previous_exception->getRawParameters();
            if ($route_name === 'entity.node.canonical' && isset($parameters['node'])) {
                // If the node_translation_redirect state is not set, we don't need to check
                // for a redirection.
                if (!$this->state
                    ->get('node_translation_redirect')) {
                    return;
                }
                $old_nid = $parameters['node'];
                $collection = $this->keyValue
                    ->get('node_translation_redirect');
                if ($old_nid && ($value = $collection->get($old_nid))) {
                    [
                        $nid,
                        $langcode,
                    ] = $value;
                    $language = $this->languageManager
                        ->getLanguage($langcode);
                    $url = $this->urlGenerator
                        ->generateFromRoute('entity.node.canonical', [
                        'node' => $nid,
                    ], [
                        'language' => $language,
                    ]);
                    $response = new RedirectResponse($url, 301);
                    $event->setResponse($response);
                }
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        $events = [];
        $events[KernelEvents::EXCEPTION] = [
            'onException',
        ];
        return $events;
    }

}