Ticket #39800: 39800.3.patch

src/wp-includes/nav-menu-template.php

@@ -394 +394 @@
                 ) {
                         $classes[] = 'current-menu-item';
                         $menu_items[$key]->current = true;
+                        $_anc_id = (int) $menu_item->db_id;
+
+                        while(
+                                ( $_anc_id = get_post_meta( $_anc_id, '_menu_item_menu_item_parent', true ) ) &&
+                                ! in_array( $_anc_id, $active_ancestor_item_ids )
+                        ) {
+                                $active_ancestor_item_ids[] = $_anc_id;
+                        }
+
+                        $active_parent_item_ids[] = (int) $menu_item->menu_item_parent;
                 // if the menu item corresponds to the currently-requested URL
                 } elseif ( 'custom' == $menu_item->object && isset( $_SERVER['HTTP_HOST'] ) ) {
                         $_root_relative_current = untrailingslashit( $_SERVER['REQUEST_URI'] );