class PathFieldItemList

class PathFieldItemList extends FieldItemList {
    use ComputedItemListTrait;
    
    /**
     * {@inheritdoc}
     */
    protected function computeValue() {
        // Default the langcode to the current language if this is a new entity or
        // there is no alias for an existent entity.
        // @todo Set the langcode to not specified for untranslatable fields
        //   in https://www.drupal.org/node/2689459.
        $value = [
            'langcode' => $this->getLangcode(),
        ];
        $entity = $this->getEntity();
        if (!$entity->isNew()) {
            
            /** @var \Drupal\path_alias\AliasRepositoryInterface $path_alias_repository */
            $path_alias_repository = \Drupal::service('path_alias.repository');
            if ($path_alias = $path_alias_repository->lookupBySystemPath('/' . $entity->toUrl()
                ->getInternalPath(), $this->getLangcode())) {
                $value = [
                    'alias' => $path_alias['alias'],
                    'pid' => $path_alias['id'],
                    'langcode' => $path_alias['langcode'],
                ];
            }
        }
        $this->list[0] = $this->createItem(0, $value);
    }
    
    /**
     * {@inheritdoc}
     */
    public function defaultAccess($operation = 'view', ?AccountInterface $account = NULL) {
        if ($operation == 'view') {
            return AccessResult::allowed();
        }
        return AccessResult::allowedIfHasPermissions($account, [
            'create url aliases',
            'administer url aliases',
        ], 'OR')->cachePerPermissions();
    }
    
    /**
     * {@inheritdoc}
     */
    public function delete() {
        // Delete all aliases associated with this entity in the current language.
        $entity = $this->getEntity();
        $path_alias_storage = \Drupal::entityTypeManager()->getStorage('path_alias');
        $entities = $path_alias_storage->loadByProperties([
            'path' => '/' . $entity->toUrl()
                ->getInternalPath(),
            'langcode' => $entity->language()
                ->getId(),
        ]);
        $path_alias_storage->delete($entities);
    }

}