Loads an array of product ids from a commerce_shipment entity using the product entity reference field on the shipment

commerce_shipment-utility_functions.patch

diff --git a/commerce_shipment.module b/commerce_shipment.module
index 8feda95..c950925 100644
--- a/commerce_shipment.module
+++ b/commerce_shipment.module
@@ -445,3 +445,50 @@ function commerce_shipment_commerce_multichannel_migration_info() {
 
   return $items;
 }
+
+/**
+ * Helper function to return product id list from shipments on an order.
+ */
+function commerce_shipment_product_id_list_from_order_shipments($order) {
+  $shipments = array();
+  if (!empty($order->commerce_shipments)) {
+    $order_wrapper = entity_metadata_wrapper('commerce_order', $order);
+    $shipments = $order_wrapper->commerce_shipments->value();
+  }
+  return commerce_shipment_product_id_list_from_shipment($shipments);
+}
+
+/**
+ * Returns a non-unique array of product ids for each shipment.
+ */
+function commerce_shipment_product_id_list_from_shipment($shipments) {
+  $product_ids = array();
+  $field_name = commerce_shipment_product_reference_field();
+  foreach ($shipments as $shipment) {
+    if (!empty($shipment->{$field_name})) {
+      $shipment_wrapper = entity_metadata_wrapper('commerce_shipment', $shipment);
+      foreach ($shipment_wrapper->{$field_name}->value() as $product) {
+        $product_ids[] = $product->product_id;
+      }
+    }
+  }
+  return $product_ids;
+}
+
+/**
+ * Defines the product reference field on shipments.
+ */
+function commerce_shipment_product_reference_field() {
+  $field_name = 'field_shipment_products';
+  drupal_alter('commerce_shipment_product_reference_field', $field_name);
+  return $field_name;
+}
+
+/**
+ * Defines the product reference field on shipments.
+ */
+function commerce_shipment_box_reference_field() {
+  $field_name = 'field_box';
+  drupal_alter('commerce_shipment_box_reference_field', $field_name);
+  return $field_name;
+}