LinkNotExistingInternalConstraintValidator.php

<?php

namespace Drupal\link\Plugin\Validation\Constraint;

use Symfony\Component\Routing\Exception\InvalidParameterException;
use Symfony\Component\Routing\Exception\MissingMandatoryParametersException;
use Symfony\Component\Routing\Exception\RouteNotFoundException;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;

/**
 * Validates the LinkNotExistingInternal constraint.
 */
class LinkNotExistingInternalConstraintValidator extends ConstraintValidator {
    
    /**
     * {@inheritdoc}
     */
    public function validate($value, Constraint $constraint) {
        if (isset($value)) {
            try {
                
                /** @var \Drupal\Core\Url $url */
                $url = $value->getUrl();
            } catch (\InvalidArgumentException $e) {
                return;
            }
            if ($url->isRouted()) {
                $allowed = TRUE;
                try {
                    $url->toString(TRUE);
                } catch (RouteNotFoundException $e) {
                    $allowed = FALSE;
                } catch (InvalidParameterException $e) {
                    $allowed = FALSE;
                } catch (MissingMandatoryParametersException $e) {
                    $allowed = FALSE;
                }
                if (!$allowed) {
                    $this->context
                        ->addViolation($constraint->message, [
                        '@uri' => $value->uri,
                    ]);
                }
            }
        }
    }

}