Moved building the edit registry to an includes function and changed teh context index.

includes/datastream.inc

@@ -294,13 +294,9 @@ function islandora_datastream_get_url(AbstractDatastream $datastream, $type = 'd
  *   The datastream to edit.
  */
 function islandora_edit_datastream(AbstractDatastream $datastream) {
-  $edit_registry = module_invoke_all('islandora_edit_datastream_registry', $datastream->parent, $datastream);
-  $context = array(
-    'datastream_parent' => $datastream->parent,
-    'datastream' => $datastream,
-    'original_edit_registry' => $edit_registry,
-  );
-  drupal_alter(ISLANDORA_EDIT_DATASTREAM_MODIFY_REGISTRY_HOOK, $edit_registry, $context);
+  module_load_include('inc', 'islandora', 'includes/utilities');
+
+  $edit_registry = islandora_build_datastream_edit_registry($datastream->parent, $datastream);
   $edit_count = count($edit_registry);
   switch ($edit_count) {
     case 0:

includes/utilities.inc

@@ -946,3 +946,25 @@ function islandora_deployed_on_windows() {
   }
   return FALSE;
 }
+
+/**
+ * Build the edit registry for a given datastream.
+ *
+ * @param AbstractObject $object
+ *   The object being edited.
+ * @param AbstractDatastream $datastream
+ *   The datastream being edited.
+ *
+ * @return array
+ *   The built edit registry array.
+ */
+function islandora_build_datastream_edit_registry($object, $datastream) {
+  $edit_registry = module_invoke_all('islandora_edit_datastream_registry', $object, $datastream);
+  $context = array(
+    'object' => $object,
+    'datastream' => $datastream,
+    'original_edit_registry' => $edit_registry,
+  );
+  drupal_alter(ISLANDORA_EDIT_DATASTREAM_MODIFY_REGISTRY_HOOK, $edit_registry, $context);
+  return $edit_registry;
+}

islandora.api.php

@@ -870,7 +870,7 @@ function hook_islandora_edit_datastream_modify_registry_alter(&$edit_registry, $
   // Add custom form to replace the removed form builder edit_form.
   $edit_registry['somemodule_custom_form'] =  array(
     'name' => t('Somemodule Custom Form'),
-    'url' => "islandora/custom_form/{$context['datastream_parent']->id}/{$context['datastream']->id}",
+    'url' => "islandora/custom_form/{$context['object']->id}/{$context['datastream']->id}",
     'weight' => 1,
   );
 }

theme/theme.inc

@@ -533,8 +533,9 @@ function theme_islandora_datastream_revert_link(array $vars) {
  */
 function theme_islandora_datastream_edit_link(array $vars) {
   $datastream = $vars['datastream'];
+  module_load_include('inc', 'islandora', 'includes/utilities');
 
-  $edit_registry = module_invoke_all('islandora_edit_datastream_registry', $datastream->parent, $datastream);
+  $edit_registry = islandora_build_datastream_edit_registry($datastream->parent, $datastream);
 
   $can_edit = count($edit_registry) > 0 && islandora_datastream_access(ISLANDORA_METADATA_EDIT, $datastream);