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
     */
    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 $constraint) {
        if (isset($value)) {
            try {
                $url = $value->getUrl();
            } catch (\InvalidArgumentException $e) {
                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) {
                $this->context
                    ->addViolation($constraint->message, [
                    '@uri' => $value->uri,
                ]);
            }
        }
    }

}