Issue #3262553 by mfb: Invalidate page & dynamic page cache after config change

services:

  hreflang.config_subscriber:

    class: Drupal\hreflang\EventSubscriber\HreflangConfigSubscriber

    arguments: ['@event_dispatcher', '@logger.channel.hreflang', '@messenger', '@?cache.dynamic_page_cache', '@?cache.page']

    tags:

      - { name: event_subscriber }

  logger.channel.hreflang:

    parent: logger.channel_base

    arguments: ['hreflang']

<?php

namespace Drupal\hreflang\EventSubscriber;

use Drupal\Core\Cache\CacheBackendInterface;

use Drupal\Core\Config\ConfigCrudEvent;

use Drupal\Core\Config\ConfigEvents;

use Drupal\Core\Messenger\MessengerInterface;

use Drupal\Core\StringTranslation\StringTranslationTrait;

use Psr\Log\LoggerInterface;

use Symfony\Component\EventDispatcher\EventDispatcherInterface;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;

use Symfony\Component\HttpKernel\KernelEvents;

/**

 * Listens to the config save event for hreflang.settings.

 */

class HreflangConfigSubscriber implements EventSubscriberInterface {

  use StringTranslationTrait;

  /**

   * The dynamic page cache.

   *

   * @var \Drupal\Core\Cache\CacheBackendInterface|null

   */

  protected $cacheDynamicPageCache;

  /**

   * The page cache.

   *

   * @var \Drupal\Core\Cache\CacheBackendInterface|null

   */

  protected $cachePage;

  /**

   * The event dispatcher.

   *

   * @var \Symfony\Component\EventDispatcher\EventDispatcherInterface

   */

  protected $eventDispatcher;

  /**

   * A logger instance.

   *

   * @var \Psr\Log\LoggerInterface

   */

  protected $logger;

  /**

   * The messenger.

   *

   * @var \Drupal\Core\Messenger\MessengerInterface

   */

  protected $messenger;

  /**

   * Constructs the HreflangConfigSubscriber.

   *

   * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface $event_dispatcher

   *   The event dispatcher.

   * @param \Psr\Log\LoggerInterface $logger

   *   A logger instance.

   * @param \Drupal\Core\Messenger\MessengerInterface $messenger

   *   The messenger.

   * @param \Drupal\Core\Cache\CacheBackendInterface|null $cache_dynamic_page_cache

   *   The dynamic page cache.

   * @param \Drupal\Core\Cache\CacheBackendInterface|null $cache_page

   *   The page cache.

   */

  public function __construct(EventDispatcherInterface $event_dispatcher, LoggerInterface $logger, MessengerInterface $messenger, ?CacheBackendInterface $cache_dynamic_page_cache = NULL, ?CacheBackendInterface $cache_page = NULL) {

    $this->cacheDynamicPageCache = $cache_dynamic_page_cache;

    $this->cachePage = $cache_page;

    $this->eventDispatcher = $event_dispatcher;

    $this->logger = $logger;

    $this->messenger = $messenger;

  }

  /**

   * Invalidates page caches on config change.

   *

   * @param \Drupal\Core\Config\ConfigCrudEvent $event

   *   The ConfigCrudEvent to process.

   */

  public function onSave(ConfigCrudEvent $event) {

    if ($event->getConfig()->getName() !== 'hreflang.settings') {

      return;

    }

    if (!$event->isChanged('x_default') && !$event->isChanged('defer_to_content_translation')) {

      return;

    }

    if (!$this->cacheDynamicPageCache && !$this->cachePage) {

      return;

    }

    $this->messenger->addStatus($this->t('Page caches are being cleared for the new settings to take effect.'));

    $listener = function () {

      if ($this->cacheDynamicPageCache) {

        $this->cacheDynamicPageCache->invalidateAll();

      }

      if ($this->cachePage) {

        $this->cachePage->invalidateAll();

      }

      $this->logger->notice($this->t('Page caches have been cleared for new Hreflang settings.'));

    };

    $this->eventDispatcher->addListener(KernelEvents::TERMINATE, $listener, 400);

  }

  /**

   * {@inheritdoc}

   */

  public static function getSubscribedEvents() {

    $events[ConfigEvents::SAVE][] = ['onSave'];

    return $events;

  }

}