lookupDestinationId

gistfile1.txt

 /**
   * Retrieves the hash of the source identifier values.
   *
   * @param array $source_id_values
   *   The source identifiers
   *
   * @return string
   *   An hash containing the hashed values of the source identifiers.
   */
     protected function getSourceIDsHash(array $source_id_values) {
        // When looking up the destination ID we require an array with both the
        // source key and value, e.g. ['nid' => 41]. In this case, $source_id_values need to be ordered the same
        // order as $this->sourceIdFields(). However, the Migration process
        // plugin doesn't currently have a way to get the source key so we presume
        // the values have been passed through in the correct order.
         if (!isset($source_id_values[0])) {
             $source_id_values = array_intersect_key($source_id_values, $this->sourceIdFields());
          }
        return  hash('sha256', serialize(array_map('strval', array_values($source_id_values))));
    }