/**
 * Implements hook_field_formatter_view().
 */
function custom_commerce_cart_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
  $settings = array_merge(field_info_formatter_settings($display['type']), $display['settings']);
  $result = array();

  // Collect the list of product IDs.
  $product_ids = array();

  foreach ($items as $delta => $item) {
    $product_ids[] = $item['product_id'];
  }

  if ($display['type'] == 'custom_commerce_cart_add_to_cart_form') {
    // Load the referenced products.
    $products = commerce_product_load_multiple($product_ids);

    // Check to ensure products are referenced, before returning results.
    if (!empty($products)) {
      if ($cache = cache_get('products_nid_' . $entity->nid)) {
        $products = $cache->data;
      } else {
        // Sort products by attribute name if exists and sort alphabetically is actived.
        // Products types with attributes, are required. If the first product have attributes, all have them it.
        if ($settings['sort_alphabetically'] && isset(current($products)->field_product_accessory[LANGUAGE_NONE]['0']['tid'])) {
          $terms = array();
          foreach ($products as $product) {
            $terms[] = $product->field_product_accessory[LANGUAGE_NONE]['0']['tid'];
          }
          $terms = taxonomy_term_load_multiple(array_unique($terms));
          foreach ($terms as $key => $term) {
            $termsSort[$key] = $term->name;
          }
          asort($termsSort);
          $tmp_products = $products;
          unset($products);
          foreach ($termsSort as $key => $term) {
            foreach ($tmp_products as $product) {
              if ($product->field_product_accessory[LANGUAGE_NONE]['0']['tid'] == $key) {
                $products[] = $product;
              }
            }
          }
          cache_set('products_nid_' . $entity->nid, $products, 'cache');
        }
      }
      $type = !empty($settings['line_item_type']) ? $settings['line_item_type'] : 'product';
      $line_item = commerce_product_line_item_new(reset($products), $settings['default_quantity'], 0, array(), $type);
      $line_item->data['context']['product_ids'] = array_keys($products);
      $line_item->data['context']['add_to_cart_combine'] = $settings['combine'];

      $result[] = array(
        '#arguments' => array(
          'form_id' => custom_commerce_cart_add_to_cart_form_id($product_ids),
          'line_item' => $line_item,
          'show_quantity' => $settings['show_quantity'],
          'sort_alphabetically' => $settings['sort_alphabetically'],
        ),
      );
    }
  }

  return $result;
}