EntityExists.php

<?php

namespace Drupal\migrate\Plugin\migrate\process;

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\EntityStorageInterface;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Drupal\migrate\Plugin\MigrationInterface;
use Drupal\migrate\MigrateExecutableInterface;
use Drupal\migrate\ProcessPluginBase;
use Drupal\migrate\Row;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * This plugin checks if a given entity exists.
 *
 * Example usage with configuration:
 * @code
 *   field_tags:
 *     plugin: entity_exists
 *     source: tid
 *     entity_type: taxonomy_term
 * @endcode
 *
 * @MigrateProcessPlugin(
 *  id = "entity_exists"
 * )
 */
class EntityExists extends ProcessPluginBase implements ContainerFactoryPluginInterface {
    
    /**
     * The entity storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $storage;
    
    /**
     * EntityExists constructor.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin ID.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param $storage
     *   The entity storage.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityStorageInterface $storage) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->storage = $storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration = NULL) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('entity_type.manager')
            ->getStorage($configuration['entity_type']));
    }
    
    /**
     * {@inheritdoc}
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        if (is_array($value)) {
            $value = reset($value);
        }
        $entity = $this->storage
            ->load($value);
        if ($entity instanceof EntityInterface) {
            return $entity->id();
        }
        return FALSE;
    }

}