Issue #1830936 by mtunay, vijaycs85: Convert the 'menu_override_parent_selector()' variable to CMI.

core/modules/book/book.module

@@ -460,7 +460,7 @@ function book_pick_book_nojs_submit($form, &$form_state) {
  *   A parent selection form element.
  */
 function _book_parent_select($book_link) {
-  if (variable_get('menu_override_parent_selector', FALSE)) {
+  if (config('menu.settings')->get('override_parent_selector')) {
     return array();
   }
   // Offer a message or a drop-down to choose a different parent page.

core/modules/menu/config/menu.settings.yml

 main_links: main
 secondary_links: account
+override_parent_selector: '0'

core/modules/menu/menu.install

@@ -115,3 +115,14 @@ function menu_update_8002() {
     ->execute();
 }
 
+/**
+ * Moves menu_override_parent_selector from variables to config.
+ *
+ * @ingroup config_upgrade
+ */
+function menu_update_8003() {
+  update_variables_to_config('menu.settings', array(
+    'menu_override_parent_selector' => 'override_parent_selector',
+  ));
+}
+

core/modules/menu/menu.module

@@ -354,14 +354,14 @@ function menu_delete($menu) {
  *   and mlid. The list excludes the given item and its children.
  *
  * @todo This has to be turned into a #process form element callback. The
- *   'menu_override_parent_selector' variable is entirely superfluous.
+ *   'override_parent_selector' variable is entirely superfluous.
  */
 function menu_parent_options($menus, $item, $type = '') {
   // The menu_links table can be practically any size and we need a way to
   // allow contrib modules to provide more scalable pattern choosers.
   // hook_form_alter is too late in itself because all the possible parents are
-  // retrieved here, unless menu_override_parent_selector is set to TRUE.
-  if (variable_get('menu_override_parent_selector', FALSE)) {
+  // retrieved here, unless override_parent_selector is set to TRUE.
+  if (config('menu.settings')->get('override_parent_selector')) {
     return array();
   }