gistfile1.php

<?php

abstract class MigrateFieldHandler extends MigrateHandler {
  // abstract function arguments(...)
  abstract public function prepare(stdClass $entity, array $field_info, array $instance, array $values);

  /**
   * Determine the language of the field
   *
   * @param $entity
   * @param $field_info
   * @param $arguments
   * @return string language code
   */
  function getFieldLanguage(stdClass $entity, $field_info, array $arguments) {
    $migration = Migration::currentMigration();
    switch (TRUE) {
      case !field_is_translatable($migration->getDestination()->getEntityType(), $field_info):
          return LANGUAGE_NONE;
      case isset($arguments['language']):
        return $arguments['language'];
      case $entity->language != LANGUAGE_NONE:
        return $entity->language;
        break;
      default:
        return $migration->getDestination()->getLanguage();
    }
  }
}