stopPublishing example

->condition('moderation_state', $non_default_states, 'IN');

      $workflow_condition_group->condition($group);
    }
    $query->condition($workflow_condition_group);

    if ($count = $query->count()->execute()) {
      $message = \Drupal::translation()->formatPlural($count, 'The @label workspace can not be published because it contains 1 item in an unpublished moderation state.', 'The @label workspace can not be published because it contains @count items in an unpublished moderation state.', [
        '@label' => $workspace->label(),
      ]);

      $event->stopPublishing();
      $event->setPublishingStoppedReason((string) $message);
    }
  }

  /** * {@inheritdoc} */
  public static function getSubscribedEvents(): array {
    $events[WorkspacePrePublishEvent::class][] = ['onWorkspacePrePublish'];
    return $events;
  }

}