Allow easily generating metatags for an entity programmatically

My initial code example:

<?php
$node = node_load(49);
$instance = 'node:' . $node->type;
$token_type = token_get_entity_mapping('entity', 'node');
$options = array(
  'entity' => $node,
  'entity_type' => 'node',
  'view_mode' => 'full',
  'token data' => array(
    $token_type => $node,
  ),
);
$metatags = metatag_metatags_view($instance, array(), $options);
?>

doesn't work.

Basically the best way seems to be to replicate metatags_entity_view() but without the specifics that make that function only work for the current page.

Like this:

<?php
/**
 * Helper function to load metatags for a given entity.
 */
function get_entity_metatags($entity_type, $entity_id, $langcode = NULL) {
  $entities = entity_load($entity_type, array($entity_id));
  $entity = reset($entities);
  list($entity_id, $revision_id, $bundle) = entity_extract_ids($entity_type, $entity);
  $revision_id = intval($revision_id);
  $instance = "{$entity_type}:{$bundle}";
  $view_mode = 'full';

  // Determine the language this entity actually uses.
  $entity_language = metatag_entity_get_language($entity_type, $entity);

  // The requested language is different to the entity's language, look for
  // a language elsewhere.
  if ($entity_language != $langcode) {
    // No language was defined for the entity.
    if ($entity_language == LANGUAGE_NONE) {
      $langcode = LANGUAGE_NONE;
    }
    else {
      $enabled_languages = field_content_languages();
      foreach (field_language($entity_type, $entity) as $field => $lang) {
        // Only accept actual language values that are properly enabled.
        if ($lang != LANGUAGE_NONE && in_array($lang, $enabled_languages)) {
          $langcode = $lang;
        }
      }
    }
  }

  // All applicable pieces for this current page.
  $cid_parts = array(
    'entity_type' => $entity_type,
    'bundle' => $bundle,
    'entity_id' => $entity_id,
    'revision_id' => $revision_id,
    'langcode' => $langcode,
    'view_mode' => $view_mode,
  );
  $cid = metatag_cache_default_cid_parts($cid_parts);

  if ($cache = metatag_cache_get('sadfasd')) {
    $output = $cache->data;
  }
  else {
    // Separate the meta tags.
    $metatags = isset($entity->metatags) ? $entity->metatags : array();

    // Build options for meta tag rendering.
    $options = array(
      'entity' => $entity,
      'entity_type' => $entity_type,
      'view_mode' => $view_mode,
    );

    // Ensure we actually pass a language object rather than language code.
    $languages = language_list();
    if (isset($languages[$langcode])) {
      $options['language'] = $languages[$langcode];
    }

    // Reload the entity object from cache as it may have been altered.
    $token_type = token_get_entity_mapping('entity', $entity_type);
    $entities = entity_load($entity_type, array($entity_id));
    $options['token data'][$token_type] = $entities[$entity_id];
    $options['entity'] = $entities[$entity_id];

    // Render the metatags and save to the cache.
    $output = metatag_metatags_view($instance, $metatags, $options);
    metatag_cache_set($cid, $output);
  }
  return $output;
}
?>

Here is a patch that makes it easy for another module to generate tags for an entity.

I included as an optional extra the metatags_get_entity_metatags() function, which further simplifies what a user would have to do to get the metatags, but maybe that part isn't really necessary.

Oops, new patch.

I don't love the idea of using entity_extract_ids() twice but the alternatives aren't really that crash hot either.

Here is a new version of the patch for latest dev.

Great, thanks!