ConfigCacheTag.php

<?php

namespace Drupal\system\EventSubscriber;

use Drupal\Core\Cache\CacheTagsInvalidatorInterface;
use Drupal\Core\Config\ConfigCrudEvent;
use Drupal\Core\Config\ConfigEvents;
use Drupal\Core\Extension\ThemeHandlerInterface;
use Drupal\Core\Theme\Registry;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * A subscriber invalidating cache tags when system config objects are saved.
 */
class ConfigCacheTag implements EventSubscriberInterface {
  
  /**
   * The theme handler.
   *
   * @var \Drupal\Core\Extension\ThemeHandlerInterface
   */
  protected $themeHandler;
  
  /**
   * The cache tags invalidator.
   *
   * @var \Drupal\Core\Cache\CacheTagsInvalidatorInterface
   */
  protected $cacheTagsInvalidator;
  
  /**
   * Constructs a ConfigCacheTag object.
   *
   * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
   *   The theme handler.
   * @param \Drupal\Core\Cache\CacheTagsInvalidatorInterface $cache_tags_invalidator
   *   The cache tags invalidator.
   * @param \Drupal\Core\Theme\Registry|null $themeRegistry
   *   The theme registry.
   */
  public function __construct(ThemeHandlerInterface $theme_handler, CacheTagsInvalidatorInterface $cache_tags_invalidator, protected ?Registry $themeRegistry = NULL) {
    $this->themeHandler = $theme_handler;
    $this->cacheTagsInvalidator = $cache_tags_invalidator;
    if ($this->themeRegistry === NULL) {
      @trigger_error('Calling ' . __METHOD__ . '() without the $themeRegistry argument is deprecated in drupal:10.2.0 and will be required in drupal:11.0.0. See https://www.drupal.org/node/3355227', E_USER_DEPRECATED);
      $this->themeRegistry = \Drupal::service('theme.registry');
    }
  }
  
  /**
   * Invalidate cache tags when particular system config objects are saved.
   *
   * @param \Drupal\Core\Config\ConfigCrudEvent $event
   *   The Event to process.
   */
  public function onSave(ConfigCrudEvent $event) {
    $config_name = $event->getConfig()
      ->getName();
    // Changing the site settings may mean a different route is selected for the
    // front page. Additionally a change to the site name or similar must
    // invalidate the render cache since this could be used anywhere.
    if ($config_name === 'system.site') {
      $this->cacheTagsInvalidator
        ->invalidateTags([
        'route_match',
        'rendered',
      ]);
    }
    // Theme configuration and global theme settings.
    if (in_array($config_name, [
      'system.theme',
      'system.theme.global',
    ], TRUE)) {
      $this->cacheTagsInvalidator
        ->invalidateTags([
        'rendered',
      ]);
    }
    // Library and template overrides potentially change for the default theme
    // when the admin theme is changed.
    if ($config_name === 'system.theme' && $event->isChanged('admin')) {
      $this->themeRegistry
        ->reset();
      $this->cacheTagsInvalidator
        ->invalidateTags([
        'library_info',
      ]);
    }
    // Theme-specific settings, check if this matches a theme settings
    // configuration object (THEME_NAME.settings), in that case, clear the
    // rendered cache tag.
    if (preg_match('/^([^\\.]*)\\.settings$/', $config_name, $matches)) {
      if ($this->themeHandler
        ->themeExists($matches[1])) {
        $this->cacheTagsInvalidator
          ->invalidateTags([
          'rendered',
        ]);
      }
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() : array {
    $events[ConfigEvents::SAVE][] = [
      'onSave',
    ];
    return $events;
  }

}