From ccf9b724462dc695a006d74117853876c441529a Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@git.wordpress.org>
Date: Mon, 21 Nov 2016 19:15:05 +0000
Subject: [PATCH] Customize: Prevent selective refresh from causing infinite
 fallback refreshes when nav menu contains invalid items.

Invalid nav menu items are exported as settings in the customize controls since it `is_admin()`, but any such `nav_menu_item` settings are excluded from the preview since it's the frontend. Selective refresh for nav menus needs to ignore the syncing of any such `nav_menu_item` settings that are `_invalid` since they are never rendered, and when a nav menu only contains invalid items, an infinite fallback refresh can ensue.

Fixes #38890.


git-svn-id: https://develop.svn.wordpress.org/trunk@39333 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/js/customize-preview-nav-menus.js | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/wp-includes/js/customize-preview-nav-menus.js b/src/wp-includes/js/customize-preview-nav-menus.js
index e7e4d14f5f..3876e4415c 100644
--- a/src/wp-includes/js/customize-preview-nav-menus.js
+++ b/src/wp-includes/js/customize-preview-nav-menus.js
@@ -23,7 +23,17 @@ wp.customize.navMenusPreview = wp.customize.MenusCustomizerPreview = ( function(
 				self.bindSettingListener( setting );
 			} );
 			api.bind( 'add', function( setting ) {
-				self.bindSettingListener( setting, { fire: true } );
+
+				/*
+				 * Handle case where an invalid nav menu item (one for which its associated object has been deleted)
+				 * is synced from the controls into the preview. Since invalid nav menu items are filtered out from
+				 * being exported to the frontend by the _is_valid_nav_menu_item filter in wp_get_nav_menu_items(),
+				 * the customizer controls will have a nav_menu_item setting where the preview will have none, and
+				 * this can trigger an infinite fallback refresh when the nav menu item lacks any valid items.
+				 */
+				if ( setting.get() && ! setting.get()._invalid ) {
+					self.bindSettingListener( setting, { fire: true } );
+				}
 			} );
 			api.bind( 'remove', function( setting ) {
 				self.unbindSettingListener( setting );