Creating a custom target for mapping

\drupal\feeds: custom target in mapping for node processor

Creating a new custom target allows to alter the data source before the mapping. For that, the hook hook_feeds_node_processor_targets_alter() needs to be implemented. There, you can specify a target name and description, a function callback that will process the data source, and a real target, corresponding to an actuel field of the content type.
After flushing the cache, a new option should be available in the target dropdown.

Example:

/**
 * Implementation of hook_feeds_node_processor_targets_alter().
 */
function feeds_library_feeds_processor_targets_alter(&$targets, $entity_type, $bundle_name){
  $targets['field_category_custom'] = array(
    'name' => t('Sujet des Articles'),
    'description' => t('Map le sujet des articles pour chaque parution'),
    'callback' => 'feeds_library_set_target',
    'real_target' => 'field_sujet_pour_document',
  );
}

function feeds_library_set_target($source, $entity, $target, $value, $mapping) {
  // Use mapping table to fetch 
  $result = db_query("SELECT m.sujet, t.tid FROM {sujets_sans_cote} m 
                        LEFT JOIN {taxonomy_term_data} t ON t.name = m.sujet 
                        WHERE m.code = :code", array(':code' => trim($value))
  );
  $record = $result->fetchObject();

  if($record) {
    $wrapper = entity_metadata_wrapper('node', $entity);
    $wrapper->field_sujet_pour_document->set($record->tid);
  } else {
    // Log this
  }
}