UniqueFieldConstraint.php

<?php

namespace Drupal\Core\Validation\Plugin\Validation\Constraint;

use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\Core\Validation\Attribute\Constraint;
use Symfony\Component\Validator\Constraint as SymfonyConstraint;

/**
 * Checks if an entity field has a unique value.
 */
class UniqueFieldConstraint extends SymfonyConstraint {
  
  /**
   * Constructs a UniqueFieldConstraint object.
   *
   * @param bool $caseSensitive
   *   This constraint is case-insensitive by default. For example, "FOO" and
   *   "foo" would be considered as equivalent, and validation of the constraint
   *   would fail.
   * @param string $message
   *   The error message.
   * @param array|null $groups
   *   The groups that the constraint belongs to.
   * @param mixed|null $payload
   *   Domain-specific data attached to a constraint.
   */
  public function __construct(public bool $caseSensitive = FALSE, public $message = 'A @entity_type with @field_name %value already exists.', ?array $groups = NULL, mixed $payload = NULL) {
    parent::__construct(groups: $groups, payload: $payload);
  }
  
  /**
   * {@inheritdoc}
   */
  public function validatedBy() : string {
    return '\\Drupal\\Core\\Validation\\Plugin\\Validation\\Constraint\\UniqueFieldValueValidator';
  }

}