UniquePathAliasConstraintValidator.php

<?php

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

use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
use Drupal\Core\Entity\EntityTypeManagerInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;

/**
 * Constraint validator for a unique path alias.
 */
class UniquePathAliasConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * Creates a new UniquePathAliasConstraintValidator instance.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager) {
        $this->entityTypeManager = $entity_type_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('entity_type.manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function validate($entity, Constraint $constraint) : void {
        
        /** @var \Drupal\path_alias\PathAliasInterface $entity */
        $path = $entity->getPath();
        $alias = $entity->getAlias();
        $langcode = $entity->language()
            ->getId();
        $storage = $this->entityTypeManager
            ->getStorage('path_alias');
        $query = $storage->getQuery()
            ->accessCheck(FALSE)
            ->condition('alias', $alias, '=')
            ->condition('langcode', $langcode, '=');
        if (!$entity->isNew()) {
            $query->condition('id', $entity->id(), '<>');
        }
        if ($path) {
            $query->condition('path', $path, '<>');
        }
        if ($result = $query->range(0, 1)
            ->execute()) {
            $existing_alias_id = reset($result);
            $existing_alias = $storage->load($existing_alias_id);
            if ($existing_alias->getAlias() !== $alias) {
                $this->context
                    ->buildViolation($constraint->differentCapitalizationMessage, [
                    '%alias' => $alias,
                    '%stored_alias' => $existing_alias->getAlias(),
                ])
                    ->addViolation();
            }
            else {
                $this->context
                    ->buildViolation($constraint->message, [
                    '%alias' => $alias,
                ])
                    ->addViolation();
            }
        }
    }

}