LinkAccessConstraintValidator.php

<?php

namespace Drupal\link\Plugin\Validation\Constraint;

use Drupal\Core\Session\AccountProxyInterface;
use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;

/**
 * Validates the LinkAccess constraint.
 */
class LinkAccessConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
  
  /**
   * Proxy for the current user account.
   *
   * @var \Drupal\Core\Session\AccountProxyInterface
   */
  // phpcs:ignore Drupal.NamingConventions.ValidVariableName.LowerCamelName, Drupal.Commenting.VariableComment.Missing
  protected $current_user;
  
  /**
   * Constructs an instance of the LinkAccessConstraintValidator class.
   *
   * @param \Drupal\Core\Session\AccountProxyInterface $current_user
   *   The current user account.
   */
  public function __construct(AccountProxyInterface $current_user) {
    $this->current_user = $current_user;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('current_user'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function validate($value, Constraint $constraint) : void {
    if (isset($value)) {
      try {
        $url = $value->getUrl();
      } catch (\InvalidArgumentException) {
        return;
      }
      // Disallow URLs if the current user doesn't have the 'link to any page'
      // permission nor can access this URI.
      $allowed = $this->current_user
        ->hasPermission('link to any page') || $url->access();
      if (!$allowed) {
        $this->context
          ->buildViolation($constraint->message, [
          '@uri' => $value->uri,
        ])
          ->atPath('uri')
          ->addViolation();
      }
    }
  }

}