validateSiteUuid example

$storage_comparer->createChangelist();
    if (empty($source_list) || !$storage_comparer->hasChanges()) {
      $form['no_changes'] = [
        '#type' => 'table',
        '#header' => [$this->t('Name'), $this->t('Operations')],
        '#rows' => [],
        '#empty' => empty($source_list) ? $this->t('There is no staged configuration.') : $this->t('The staged configuration is identical to the active configuration.'),
      ];
      $form['actions']['#access'] = FALSE;
      return $form;
    }
    elseif (!$storage_comparer->validateSiteUuid()) {
      $this->messenger()->addError($this->t('The staged configuration cannot be imported, because it originates from a different site than this site. You can only synchronize configuration between cloned instances of this site.'));
      $form['actions']['#access'] = FALSE;
      return $form;
    }
    // A list of changes will be displayed, so check if the user should be     // warned of potential losses to configuration.     if ($this->snapshotStorage->exists('core.extension')) {
      $snapshot_comparer = new StorageComparer($this->activeStorage, $this->snapshotStorage);
      $snapshot_comparer->createChangelist();
      if (!$form_state->getUserInput() && $snapshot_comparer->hasChanges()) {
        $change_list = [];
        

  public function onConfigImporterValidateSiteUUID(ConfigImporterEvent $event) {
    if (!$event->getConfigImporter()->getStorageComparer()->getSourceStorage()->exists('system.site')) {
      $event->getConfigImporter()->logError($this->t('This import does not contain system.site configuration, so has been rejected.'));
    }
    if (!$event->getConfigImporter()->getStorageComparer()->validateSiteUuid()) {
      $event->getConfigImporter()->logError($this->t('Site UUID in source storage does not match the target storage.'));
    }
  }

  /** * {@inheritdoc} */
  public static function getSubscribedEvents(): array {
    $events[ConfigEvents::SAVE][] = ['onConfigSave', 0];
    // The empty check has a high priority so that it can stop propagation if     // there is no configuration to import.