When splitting a shared 'nav_menu' term, ensure that nav items and theme locations are retained.

Props boonebgorges, dd32.
Fixes #33187.

git-svn-id: https://develop.svn.wordpress.org/trunk@33611 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/default-filters.php

@@ -330,6 +330,7 @@ add_filter( 'determine_current_user', 'wp_validate_logged_in_cookie', 20 );
 // Split term updates.
 add_action( 'split_shared_term', '_wp_check_split_default_terms',  10, 4 );
 add_action( 'split_shared_term', '_wp_check_split_terms_in_menus', 10, 4 );
+add_action( 'split_shared_term', '_wp_check_split_nav_menu_terms', 10, 4 );
 
 /**
  * Filters formerly mixed into wp-includes

src/wp-includes/nav-menu.php

@@ -315,6 +315,8 @@ function wp_update_nav_menu_object( $menu_id = 0, $menu_data = array() ) {
 	if ( is_wp_error( $update_response ) )
 		return $update_response;
 
+	$menu_id = (int) $update_response['term_id'];
+
 	/**
 	 * Fires after a navigation menu has been successfully updated.
 	 *

src/wp-includes/taxonomy.php

@@ -4395,6 +4395,34 @@ function _wp_check_split_terms_in_menus( $term_id, $new_term_id, $term_taxonomy_
 	}
 }
 
+/**
+ * If the term being split is a nav_menu, change associations.
+ *
+ * @ignore
+ * @since 4.3.0
+ *
+ * @global wpdb $wpdb
+ *
+ * @param int    $term_id          ID of the formerly shared term.
+ * @param int    $new_term_id      ID of the new term created for the $term_taxonomy_id.
+ * @param int    $term_taxonomy_id ID for the term_taxonomy row affected by the split.
+ * @param string $taxonomy         Taxonomy for the split term.
+ */
+function _wp_check_split_nav_menu_terms( $term_id, $new_term_id, $term_taxonomy_id, $taxonomy ) {
+	if ( 'nav_menu' !== $taxonomy ) {
+		return;
+	}
+
+	// Update menu locations.
+	$locations = get_nav_menu_locations();
+	foreach ( $locations as $location => $menu_id ) {
+		if ( $term_id == $menu_id ) {
+			$locations[ $location ] = $new_term_id;
+		}
+	}
+	set_theme_mod( 'nav_menu_locations', $locations );
+}
+
 /**
  * Get data about terms that previously shared a single term_id, but have since been split.
  *