EntityTypeConstraint.php

<?php

/**
 * @file
 * Contains \Drupal\Core\Validation\Constraint\EntityTypeConstraint.
 */
namespace Drupal\Core\Validation\Plugin\Validation\Constraint;

use Symfony\Component\Validator\Constraint;
use Drupal\Component\Annotation\Plugin;
use Drupal\Core\Annotation\Translation;

/**
 * Checks if a value is a valid entity type.
 *
 * @todo: Move this below the entity core component.
 *
 * @Plugin(
 *   id = "EntityType",
 *   label = @Translation("Entity type", context = "Validation"),
 *   type = "entity"
 * )
 */
class EntityTypeConstraint extends Constraint {

  /**
   * The default violation message.
   *
   * @var string
   */
  public $message = 'The entity must be of type %type.';

  /**
   * The entity type option.
   *
   * @var string
   */
  public $type;

  /**
   * Overrides Constraint::getDefaultOption().
   */
  public function getDefaultOption() {
    return 'type';
  }

  /**
   * Overrides Constraint::getRequiredOptions().
   */
  public function getRequiredOptions() {
    return array(
      'type',
    );
  }

}