drupal_module__reinstall/src/EventSubscriber/IdPostRowSave.php

<?php

namespace Drupal\reinstall\EventSubscriber;

use Drupal\Component\Utility\NestedArray;
use Drupal\migrate\Event\MigrateEvents;
use Drupal\migrate\Event\MigratePostRowSaveEvent;
use Drupal\migrate\Row;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * Class IdPostRowSave normalizes ids after the destination saved the row.
 *
 * This is needed because raw reinstall sources do not flatten source values,
 * and Sql::saveIdMap() assumes property fields are scalars of the described
 * type for the source, so we need to overwrite the source value for this last
 * step.
 *
 * Example: a node has an integer "nid" key, but is dumped like:
 * <nid>:
 *   nid:
 *     -
 *       value: 2
 *   ...
 */
class IdPostRowSave implements EventSubscriberInterface {

  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() {
    $events = [
      MigrateEvents::POST_ROW_SAVE => 'postRowSave',
    ];

    return $events;
  }

  /**
   * Callback for POST_ROW_SAVE.
   *
   * @param \Drupal\migrate\Event\MigratePostRowSaveEvent $event
   *   The event instance.
   */
  public function postRowSave(MigratePostRowSaveEvent $event) {
    $row = $event->getRow();
    $idValues = $row->getSourceIdValues();
    foreach ($idValues as $idName => $idValue) {
      $current = $idValue;
      while (is_array($current)) {
        $current = current($current);
      }
      // Unavailable because source is frozen at this point.
      // $row->setSourceProperty($idName, $current);
      // So let's use brute force.
      NestedArray::setValue($row->getSource(), explode(Row::PROPERTY_SEPARATOR, $idName), $current, TRUE);
    }
  }

}