Ticket #18282: preserve-page-and-taxonomy-hierarchy.php

<?php
/*
Plugin Name: Preserve Page and Taxonomy Hierarchy on Edit Menus Screen
Version: 0.1
Plugin URI: https://core.trac.wordpress.org/ticket/18282
Description: Disables paging for hierarchical post types and taxonomies on Edit Menus screen to preserve proper hierarchy in meta boxes.
Author: Sergey Biryukov
Author URI: http://profiles.wordpress.org/sergeybiryukov/
*/

class Preserve_Page_and_Taxonomy_Hierarchy {

        function __construct() {
                add_action( 'load-nav-menus.php', array( $this, 'init' ) );
        }

        function init() {
                add_action( 'pre_get_posts',    array( $this, 'disable_paging_for_hierarchical_post_types' ) );
                add_filter( 'get_terms_args',   array( $this, 'remove_limit_for_hierarchical_taxonomies' ), 10, 2 );
                add_filter( 'get_terms_fields', array( $this, 'remove_page_links_for_hierarchical_taxonomies' ), 10, 3 );
        }

        function disable_paging_for_hierarchical_post_types( $query ) {
                if ( ! is_admin() || 'nav-menus' !== get_current_screen()->id ) {
                        return;
                }

                if ( ! is_post_type_hierarchical( $query->get( 'post_type' ) ) ) {
                        return;
                }

                if ( 50 == $query->get( 'posts_per_page' ) ) {
                        $query->set( 'nopaging', true );
                }
        }

        function remove_limit_for_hierarchical_taxonomies( $args, $taxonomies ) {
                if ( ! is_admin() || 'nav-menus' !== get_current_screen()->id ) {
                        return $args;
                }

                if ( ! is_taxonomy_hierarchical( reset( $taxonomies ) ) ) {
                        return $args;
                }

                if ( 50 == $args['number'] ) {
                        $args['number'] = '';
                }

                return $args;
        }

        function remove_page_links_for_hierarchical_taxonomies( $selects, $args, $taxonomies ) {
                if ( ! is_admin() || 'nav-menus' !== get_current_screen()->id ) {
                        return $selects;
                }

                if ( ! is_taxonomy_hierarchical( reset( $taxonomies ) ) ) {
                        return $selects;
                }

                if ( 'count' === $args['fields'] ) {
                        $selects = array( '1' );
                }

                return $selects;
        }

}

new Preserve_Page_and_Taxonomy_Hierarchy;
?>