UriHostConstraint.php

<?php

declare (strict_types=1);
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 a string conforms to the RFC 3986 host component.
 */
class UriHostConstraint extends SymfonyConstraint {
    
    /**
     * The error message if validation fails.
     *
     * @var string
     */
    public string $message = 'This value should conform to RFC 3986 URI host component.';

}