class PendingUpdatesValidator

final class PendingUpdatesValidator implements EventSubscriberInterface {
    use StringTranslationTrait;
    public function __construct(string $appRoot, UpdateRegistry $updateRegistry) {
    }
    
    /**
     * Validates that there are no pending database updates.
     */
    public function validate(PreOperationStageEvent $event) : void {
        if ($this->updatesExist()) {
            $message = $this->t('Some modules have database updates pending. You should run the <a href=":update">database update script</a> immediately.', [
                ':update' => Url::fromRoute('system.db_update')->toString(),
            ]);
            $event->addError([
                $message,
            ]);
        }
    }
    
    /**
     * Checks if there are any pending update or post-update hooks.
     *
     * @return bool
     *   TRUE if there are any pending update or post-update hooks, FALSE
     *   otherwise.
     */
    public function updatesExist() : bool {
        require_once $this->appRoot . '/core/includes/install.inc';
        require_once $this->appRoot . '/core/includes/update.inc';
        drupal_load_updates();
        $hook_updates = update_get_update_list();
        $post_updates = $this->updateRegistry
            ->getPendingUpdateFunctions();
        return $hook_updates || $post_updates;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        return [
            PreCreateEvent::class => 'validate',
            StatusCheckEvent::class => 'validate',
            PreApplyEvent::class => 'validate',
        ];
    }

}