class DeletedWorkspaceConstraintValidator

class DeletedWorkspaceConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
  
  /**
   * The state service.
   *
   * @var \Drupal\Core\State\StateInterface
   */
  protected $state;
  
  /**
   * Creates a new DeletedWorkspaceConstraintValidator instance.
   *
   * @param \Drupal\Core\State\StateInterface $state
   *   The state service.
   */
  public function __construct(StateInterface $state) {
    $this->state = $state;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('state'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function validate($value, Constraint $constraint) {
    /** @var \Drupal\Core\Field\FieldItemListInterface $value */
    // This constraint applies only to newly created workspace entities.
    if (!isset($value) || !$value->getEntity()
      ->isNew()) {
      return;
    }
    $deleted_workspace_ids = $this->state
      ->get('workspace.deleted', []);
    if (isset($deleted_workspace_ids[$value->getEntity()
      ->id()])) {
      $this->context
        ->addViolation($constraint->message);
    }
  }

}