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Editing: class-wp-customize-nav-menu-item-setting.php

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<?php
/**
 * Customize API: WP_Customize_Nav_Menu_Item_Setting class
 *
 * @package WordPress
 * @subpackage Customize
 * @since 4.4.0
 */

/**
 * Customize Setting to represent a nav_menu.
 *
 * Subclass of WP_Customize_Setting to represent a nav_menu taxonomy term, and
 * the IDs for the nav_menu_items associated with the nav menu.
 *
 * @since 4.3.0
 *
 * @see WP_Customize_Setting
 */
class WP_Customize_Nav_Menu_Item_Setting extends WP_Customize_Setting {

const ID_PATTERN = '/^nav_menu_item\[(?P<id>-?\d+)\]$/';

const POST_TYPE = 'nav_menu_item';

const TYPE = 'nav_menu_item';

/**
	 * Setting type.
	 *
	 * @since 4.3.0
	 * @var string
	 */
	public $type = self::TYPE;

/**
	 * Default setting value.
	 *
	 * @since 4.3.0
	 * @var array
	 *
	 * @see wp_setup_nav_menu_item()
	 */
	public $default = array(
		// The $menu_item_data for wp_update_nav_menu_item().
		'object_id'        => 0,
		'object'           => '', // Taxonomy name.
		'menu_item_parent' => 0, // A.K.A. menu-item-parent-id; note that post_parent is different, and not included.
		'position'         => 0, // A.K.A. menu_order.
		'type'             => 'custom', // Note that type_label is not included here.
		'title'            => '',
		'url'              => '',
		'target'           => '',
		'attr_title'       => '',
		'description'      => '',
		'classes'          => '',
		'xfn'              => '',
		'status'           => 'publish',
		'original_title'   => '',
		'nav_menu_term_id' => 0, // This will be supplied as the $menu_id arg for wp_update_nav_menu_item().
		'_invalid'         => false,
	);

/**
	 * Default transport.
	 *
	 * @since 4.3.0
	 * @since 4.5.0 Default changed to 'refresh'
	 * @var string
	 */
	public $transport = 'refresh';

/**
	 * The post ID represented by this setting instance. This is the db_id.
	 *
	 * A negative value represents a placeholder ID for a new menu not yet saved.
	 *
	 * @since 4.3.0
	 * @var int
	 */
	public $post_id;

/**
	 * Storage of pre-setup menu item to prevent wasted calls to wp_setup_nav_menu_item().
	 *
	 * @since 4.3.0
	 * @var array|null
	 */
	protected $value;

/**
	 * Previous (placeholder) post ID used before creating a new menu item.
	 *
	 * This value will be exported to JS via the customize_save_response filter
	 * so that JavaScript can update the settings to refer to the newly-assigned
	 * post ID. This value is always negative to indicate it does not refer to
	 * a real post.
	 *
	 * @since 4.3.0
	 * @var int
	 *
	 * @see WP_Customize_Nav_Menu_Item_Setting::update()
	 * @see WP_Customize_Nav_Menu_Item_Setting::amend_customize_save_response()
	 */
	public $previous_post_id;

/**
	 * When previewing or updating a menu item, this stores the previous nav_menu_term_id
	 * which ensures that we can apply the proper filters.
	 *
	 * @since 4.3.0
	 * @var int
	 */
	public $original_nav_menu_term_id;

/**
	 * Whether or not update() was called.
	 *
	 * @since 4.3.0
	 * @var bool
	 */
	protected $is_updated = false;

/**
	 * Status for calling the update method, used in customize_save_response filter.
	 *
	 * See {@see 'customize_save_response'}.
	 *
	 * When status is inserted, the placeholder post ID is stored in $previous_post_id.
	 * When status is error, the error is stored in $update_error.
	 *
	 * @since 4.3.0
	 * @var string updated|inserted|deleted|error
	 *
	 * @see WP_Customize_Nav_Menu_Item_Setting::update()
	 * @see WP_Customize_Nav_Menu_Item_Setting::amend_customize_save_response()
	 */
	public $update_status;

/**
	 * Any error object returned by wp_update_nav_menu_item() when setting is updated.
	 *
	 * @since 4.3.0
	 * @var WP_Error
	 *
	 * @see WP_Customize_Nav_Menu_Item_Setting::update()
	 * @see WP_Customize_Nav_Menu_Item_Setting::amend_customize_save_response()
	 */
	public $update_error;

/**
	 * Constructor.
	 *
	 * Any supplied $args override class property defaults.
	 *
	 * @since 4.3.0
	 *
	 * @throws Exception If $id is not valid for this setting type.
	 *
	 * @param WP_Customize_Manager $manager Customizer bootstrap instance.
	 * @param string               $id      A specific ID of the setting.
	 *                                      Can be a theme mod or option name.
	 * @param array                $args    Optional. Setting arguments.
	 */
	public function __construct( WP_Customize_Manager $manager, $id, array $args = array() ) {
		if ( empty( $manager->nav_menus ) ) {
			throw new Exception( 'Expected WP_Customize_Manager::$nav_menus to be set.' );
		}

if ( ! preg_match( self::ID_PATTERN, $id, $matches ) ) {
			throw new Exception( "Illegal widget setting ID: $id" );
		}

$this->post_id = (int) $matches['id'];
		add_action( 'wp_update_nav_menu_item', array( $this, 'flush_cached_value' ), 10, 2 );

parent::__construct( $manager, $id, $args );

// Ensure that an initially-supplied value is valid.
		if ( isset( $this->value ) ) {
			$this->populate_value();
			foreach ( array_diff( array_keys( $this->default ), array_keys( $this->value ) ) as $missing ) {
				throw new Exception( "Supplied nav_menu_item value missing property: $missing" );
			}
		}
	}

/**
	 * Clear the cached value when this nav menu item is updated.
	 *
	 * @since 4.3.0
	 *
	 * @param int $menu_id       The term ID for the menu.
	 * @param int $menu_item_id  The post ID for the menu item.
	 */
	public function flush_cached_value( $menu_id, $menu_item_id ) {
		unset( $menu_id );
		if ( $menu_item_id === $this->post_id ) {
			$this->value = null;
		}
	}

/**
	 * Get the instance data for a given nav_menu_item setting.
	 *
	 * @since 4.3.0
	 *
	 * @see wp_setup_nav_menu_item()
	 *
	 * @return array|false Instance data array, or false if the item is marked for deletion.
	 */
	public function value() {
		if ( $this->is_previewed && get_current_blog_id() === $this->_previewed_blog_id ) {
			$undefined  = new stdClass(); // Symbol.
			$post_value = $this->post_value( $undefined );

if ( $undefined === $post_value ) {
				$value = $this->_original_value;
			} else {
				$value = $post_value;
			}
			if ( ! empty( $value ) && empty( $value['original_title'] ) ) {
				$value['original_title'] = $this->get_original_title( (object) $value );
			}
		} elseif ( isset( $this->value ) ) {
			$value = $this->value;
		} else {
			$value = false;

// Note that an ID of less than one indicates a nav_menu not yet inserted.
			if ( $this->post_id > 0 ) {
				$post = get_post( $this->post_id );
				if ( $post && self::POST_TYPE === $post->post_type ) {
					$is_title_empty = empty( $post->post_title );
					$value          = (array) wp_setup_nav_menu_item( $post );
					if ( $is_title_empty ) {
						$value['title'] = '';
					}
				}
			}

if ( ! is_array( $value ) ) {
				$value = $this->default;
			}

// Cache the value for future calls to avoid having to re-call wp_setup_nav_menu_item().
			$this->value = $value;
			$this->populate_value();
			$value = $this->value;
		}

if ( ! empty( $value ) && empty( $value['type_label'] ) ) {
			$value['type_label'] = $this->get_type_label( (object) $value );
		}

return $value;
	}

/**
	 * Get original title.
	 *
	 * @since 4.7.0
	 *
	 * @param object $item Nav menu item.
	 * @return string The original title.
	 */
	protected function get_original_title( $item ) {
		$original_title = '';
		if ( 'post_type' === $item->type && ! empty( $item->object_id ) ) {
			$original_object = get_post( $item->object_id );
			if ( $original_object ) {
				/** This filter is documented in wp-includes/post-template.php */
				$original_title = apply_filters( 'the_title', $original_object->post_title, $original_object->ID );

if ( '' === $original_title ) {
					/* translators: %d: ID of a post. */
					$original_title = sprintf( __( '#%d (no title)' ), $original_object->ID );
				}
			}
		} elseif ( 'taxonomy' === $item->type && ! empty( $item->object_id ) ) {
			$original_term_title = get_term_field( 'name', $item->object_id, $item->object, 'raw' );
			if ( ! is_wp_error( $original_term_title ) ) {
				$original_title = $original_term_title;
			}
		} elseif ( 'post_type_archive' === $item->type ) {
			$original_object = get_post_type_object( $item->object );
			if ( $original_object ) {
				$original_title = $original_object->labels->archives;
			}
		}
		$original_title = html_entity_decode( $original_title, ENT_QUOTES, get_bloginfo( 'charset' ) );
		return $original_title;
	}

/**
	 * Get type label.
	 *
	 * @since 4.7.0
	 *
	 * @param object $item Nav menu item.
	 * @return string The type label.
	 */
	protected function get_type_label( $item ) {
		if ( 'post_type' === $item->type ) {
			$object = get_post_type_object( $item->object );
			if ( $object ) {
				$type_label = $object->labels->singular_name;
			} else {
				$type_label = $item->object;
			}
		} elseif ( 'taxonomy' === $item->type ) {
			$object = get_taxonomy( $item->object );
			if ( $object ) {
				$type_label = $object->labels->singular_name;
			} else {
				$type_label = $item->object;
			}
		} elseif ( 'post_type_archive' === $item->type ) {
			$type_label = __( 'Post Type Archive' );
		} else {
			$type_label = __( 'Custom Link' );
		}
		return $type_label;
	}

/**
	 * Ensure that the value is fully populated with the necessary properties.
	 *
	 * Translates some properties added by wp_setup_nav_menu_item() and removes others.
	 *
	 * @since 4.3.0
	 *
	 * @see WP_Customize_Nav_Menu_Item_Setting::value()
	 */
	protected function populate_value() {
		if ( ! is_array( $this->value ) ) {
			return;
		}

if ( isset( $this->value['menu_order'] ) ) {
			$this->value['position'] = $this->value['menu_order'];
			unset( $this->value['menu_order'] );
		}
		if ( isset( $this->value['post_status'] ) ) {
			$this->value['status'] = $this->value['post_status'];
			unset( $this->value['post_status'] );
		}

if ( ! isset( $this->value['original_title'] ) ) {
			$this->value['original_title'] = $this->get_original_title( (object) $this->value );
		}

if ( ! isset( $this->value['nav_menu_term_id'] ) && $this->post_id > 0 ) {
			$menus = wp_get_post_terms(
				$this->post_id,
				WP_Customize_Nav_Menu_Setting::TAXONOMY,
				array(
					'fields' => 'ids',
				)
			);
			if ( ! empty( $menus ) ) {
				$this->value['nav_menu_term_id'] = array_shift( $menus );
			} else {
				$this->value['nav_menu_term_id'] = 0;
			}
		}

foreach ( array( 'object_id', 'menu_item_parent', 'nav_menu_term_id' ) as $key ) {
			if ( ! is_int( $this->value[ $key ] ) ) {
				$this->value[ $key ] = (int) $this->value[ $key ];
			}
		}
		foreach ( array( 'classes', 'xfn' ) as $key ) {
			if ( is_array( $this->value[ $key ] ) ) {
				$this->value[ $key ] = implode( ' ', $this->value[ $key ] );
			}
		}

if ( ! isset( $this->value['title'] ) ) {
			$this->value['title'] = '';
		}

if ( ! isset( $this->value['_invalid'] ) ) {
			$this->value['_invalid'] = false;
			$is_known_invalid        = (
				( ( 'post_type' === $this->value['type'] || 'post_type_archive' === $this->value['type'] ) && ! post_type_exists( $this->value['object'] ) )
				||
				( 'taxonomy' === $this->value['type'] && ! taxonomy_exists( $this->value['object'] ) )
			);
			if ( $is_known_invalid ) {
				$this->value['_invalid'] = true;
			}
		}

// Remove remaining properties available on a setup nav_menu_item post object which aren't relevant to the setting value.
		$irrelevant_properties = array(
			'ID',
			'comment_count',
			'comment_status',
			'db_id',
			'filter',
			'guid',
			'ping_status',
			'pinged',
			'post_author',
			'post_content',
			'post_content_filtered',
			'post_date',
			'post_date_gmt',
			'post_excerpt',
			'post_mime_type',
			'post_modified',
			'post_modified_gmt',
			'post_name',
			'post_parent',
			'post_password',
			'post_title',
			'post_type',
			'to_ping',
		);
		foreach ( $irrelevant_properties as $property ) {
			unset( $this->value[ $property ] );
		}
	}

/**
	 * Handle previewing the setting.
	 *
	 * @since 4.3.0
	 * @since 4.4.0 Added boolean return value.
	 *
	 * @see WP_Customize_Manager::post_value()
	 *
	 * @return bool False if method short-circuited due to no-op.
	 */
	public function preview() {
		if ( $this->is_previewed ) {
			return false;
		}

$undefined      = new stdClass();
		$is_placeholder = ( $this->post_id < 0 );
		$is_dirty       = ( $undefined !== $this->post_value( $undefined ) );
		if ( ! $is_placeholder && ! $is_dirty ) {
			return false;
		}

$this->is_previewed              = true;
		$this->_original_value           = $this->value();
		$this->original_nav_menu_term_id = $this->_original_value['nav_menu_term_id'];
		$this->_previewed_blog_id        = get_current_blog_id();

add_filter( 'wp_get_nav_menu_items', array( $this, 'filter_wp_get_nav_menu_items' ), 10, 3 );

$sort_callback = array( __CLASS__, 'sort_wp_get_nav_menu_items' );
		if ( ! has_filter( 'wp_get_nav_menu_items', $sort_callback ) ) {
			add_filter( 'wp_get_nav_menu_items', array( __CLASS__, 'sort_wp_get_nav_menu_items' ), 1000, 3 );
		}

// @todo Add get_post_metadata filters for plugins to add their data.

return true;
	}

/**
	 * Filters the wp_get_nav_menu_items() result to supply the previewed menu items.
	 *
	 * @since 4.3.0
	 *
	 * @see wp_get_nav_menu_items()
	 *
	 * @param WP_Post[] $items An array of menu item post objects.
	 * @param WP_Term   $menu  The menu object.
	 * @param array     $args  An array of arguments used to retrieve menu item objects.
	 * @return WP_Post[] Array of menu item objects.
	 */
	public function filter_wp_get_nav_menu_items( $items, $menu, $args ) {
		$this_item                = $this->value();
		$current_nav_menu_term_id = null;
		if ( isset( $this_item['nav_menu_term_id'] ) ) {
			$current_nav_menu_term_id = $this_item['nav_menu_term_id'];
			unset( $this_item['nav_menu_term_id'] );
		}

$should_filter = (
			$menu->term_id === $this->original_nav_menu_term_id
			||
			$menu->term_id === $current_nav_menu_term_id
		);
		if ( ! $should_filter ) {
			return $items;
		}

// Handle deleted menu item, or menu item moved to another menu.
		$should_remove = (
			false === $this_item
			||
			( isset( $this_item['_invalid'] ) && true === $this_item['_invalid'] )
			||
			(
				$this->original_nav_menu_term_id === $menu->term_id
				&&
				$current_nav_menu_term_id !== $this->original_nav_menu_term_id
			)
		);
		if ( $should_remove ) {
			$filtered_items = array();
			foreach ( $items as $item ) {
				if ( $item->db_id !== $this->post_id ) {
					$filtered_items[] = $item;
				}
			}
			return $filtered_items;
		}

$mutated       = false;
		$should_update = (
			is_array( $this_item )
			&&
			$current_nav_menu_term_id === $menu->term_id
		);
		if ( $should_update ) {
			foreach ( $items as $item ) {
				if ( $item->db_id === $this->post_id ) {
					foreach ( get_object_vars( $this->value_as_wp_post_nav_menu_item() ) as $key => $value ) {
						$item->$key = $value;
					}
					$mutated = true;
				}
			}

// Not found so we have to append it..
			if ( ! $mutated ) {
				$items[] = $this->value_as_wp_post_nav_menu_item();
			}
		}

return $items;
	}

/**
	 * Re-apply the tail logic also applied on $items by wp_get_nav_menu_items().
	 *
	 * @since 4.3.0
	 *
	 * @see wp_get_nav_menu_items()
	 *
	 * @param WP_Post[] $items An array of menu item post objects.
	 * @param WP_Term   $menu  The menu object.
	 * @param array     $args  An array of arguments used to retrieve menu item objects.
	 * @return WP_Post[] Array of menu item objects.
	 */
	public static function sort_wp_get_nav_menu_items( $items, $menu, $args ) {
		// @todo We should probably re-apply some constraints imposed by $args.
		unset( $args['include'] );

// Remove invalid items only in front end.
		if ( ! is_admin() ) {
			$items = array_filter( $items, '_is_valid_nav_menu_item' );
		}

if ( ARRAY_A === $args['output'] ) {
			$items = wp_list_sort(
				$items,
				array(
					$args['output_key'] => 'ASC',
				)
			);
			$i     = 1;

foreach ( $items as $k => $item ) {
				$items[ $k ]->{$args['output_key']} = $i++;
			}
		}

return $items;
	}

/**
	 * Get the value emulated into a WP_Post and set up as a nav_menu_item.
	 *
	 * @since 4.3.0
	 *
	 * @return WP_Post With wp_setup_nav_menu_item() applied.
	 */
	public function value_as_wp_post_nav_menu_item() {
		$item = (object) $this->value();
		unset( $item->nav_menu_term_id );

$item->post_status = $item->status;
		unset( $item->status );

$item->post_type  = 'nav_menu_item';
		$item->menu_order = $item->position;
		unset( $item->position );

if ( empty( $item->original_title ) ) {
			$item->original_title = $this->get_original_title( $item );
		}
		if ( empty( $item->title ) && ! empty( $item->original_title ) ) {
			$item->title = $item->original_title;
		}
		if ( $item->title ) {
			$item->post_title = $item->title;
		}

// 'classes' should be an array, as in wp_setup_nav_menu_item().
		if ( isset( $item->classes ) && is_scalar( $item->classes ) ) {
			$item->classes = explode( ' ', $item->classes );
		}

$item->ID    = $this->post_id;
		$item->db_id = $this->post_id;
		$post        = new WP_Post( (object) $item );

if ( empty( $post->post_author ) ) {
			$post->post_author = get_current_user_id();
		}

if ( ! isset( $post->type_label ) ) {
			$post->type_label = $this->get_type_label( $post );
		}

// Ensure nav menu item URL is set according to linked object.
		if ( 'post_type' === $post->type && ! empty( $post->object_id ) ) {
			$post->url = get_permalink( $post->object_id );
		} elseif ( 'taxonomy' === $post->type && ! empty( $post->object ) && ! empty( $post->object_id ) ) {
			$post->url = get_term_link( (int) $post->object_id, $post->object );
		} elseif ( 'post_type_archive' === $post->type && ! empty( $post->object ) ) {
			$post->url = get_post_type_archive_link( $post->object );
		}
		if ( is_wp_error( $post->url ) ) {
			$post->url = '';
		}

/** This filter is documented in wp-includes/nav-menu.php */
		$post->attr_title = apply_filters( 'nav_menu_attr_title', $post->attr_title );

/** This filter is documented in wp-includes/nav-menu.php */
		$post->description = apply_filters( 'nav_menu_description', wp_trim_words( $post->description, 200 ) );

/** This filter is documented in wp-includes/nav-menu.php */
		$post = apply_filters( 'wp_setup_nav_menu_item', $post );

return $post;
	}

/**
	 * Sanitize an input.
	 *
	 * Note that parent::sanitize() erroneously does wp_unslash() on $value, but
	 * we remove that in this override.
	 *
	 * @since 4.3.0
	 * @since 5.9.0 Renamed `$menu_item_value` to `$value` for PHP 8 named parameter support.
	 *
	 * @param array $value The menu item value to sanitize.
	 * @return array|false|null|WP_Error Null or WP_Error if an input isn't valid. False if it is marked for deletion.
	 *                                   Otherwise the sanitized value.
	 */
	public function sanitize( $value ) {
		// Restores the more descriptive, specific name for use within this method.
		$menu_item_value = $value;

// Menu is marked for deletion.
		if ( false === $menu_item_value ) {
			return $menu_item_value;
		}

// Invalid.
		if ( ! is_array( $menu_item_value ) ) {
			return null;
		}

$default                     = array(
			'object_id'        => 0,
			'object'           => '',
			'menu_item_parent' => 0,
			'position'         => 0,
			'type'             => 'custom',
			'title'            => '',
			'url'              => '',
			'target'           => '',
			'attr_title'       => '',
			'description'      => '',
			'classes'          => '',
			'xfn'              => '',
			'status'           => 'publish',
			'original_title'   => '',
			'nav_menu_term_id' => 0,
			'_invalid'         => false,
		);
		$menu_item_value             = array_merge( $default, $menu_item_value );
		$menu_item_value             = wp_array_slice_assoc( $menu_item_value, array_keys( $default ) );
		$menu_item_value['position'] = (int) $menu_item_value['position'];

foreach ( array( 'object_id', 'menu_item_parent', 'nav_menu_term_id' ) as $key ) {
			// Note we need to allow negative-integer IDs for previewed objects not inserted yet.
			$menu_item_value[ $key ] = (int) $menu_item_value[ $key ];
		}

foreach ( array( 'type', 'object', 'target' ) as $key ) {
			$menu_item_value[ $key ] = sanitize_key( $menu_item_value[ $key ] );
		}

foreach ( array( 'xfn', 'classes' ) as $key ) {
			$value = $menu_item_value[ $key ];
			if ( ! is_array( $value ) ) {
				$value = explode( ' ', $value );
			}
			$menu_item_value[ $key ] = implode( ' ', array_map( 'sanitize_html_class', $value ) );
		}

$menu_item_value['original_title'] = sanitize_text_field( $menu_item_value['original_title'] );

// Apply the same filters as when calling wp_insert_post().

/** This filter is documented in wp-includes/post.php */
		$menu_item_value['title'] = wp_unslash( apply_filters( 'title_save_pre', wp_slash( $menu_item_value['title'] ) ) );

/** This filter is documented in wp-includes/post.php */
		$menu_item_value['attr_title'] = wp_unslash( apply_filters( 'excerpt_save_pre', wp_slash( $menu_item_value['attr_title'] ) ) );

/** This filter is documented in wp-includes/post.php */
		$menu_item_value['description'] = wp_unslash( apply_filters( 'content_save_pre', wp_slash( $menu_item_value['description'] ) ) );

if ( '' !== $menu_item_value['url'] ) {
			$menu_item_value['url'] = sanitize_url( $menu_item_value['url'] );
			if ( '' === $menu_item_value['url'] ) {
				return new WP_Error( 'invalid_url', __( 'Invalid URL.' ) ); // Fail sanitization if URL is invalid.
			}
		}
		if ( 'publish' !== $menu_item_value['status'] ) {
			$menu_item_value['status'] = 'draft';
		}

$menu_item_value['_invalid'] = (bool) $menu_item_value['_invalid'];

/** This filter is documented in wp-includes/class-wp-customize-setting.php */
		return apply_filters( "customize_sanitize_{$this->id}", $menu_item_value, $this );
	}

/**
	 * Creates/updates the nav_menu_item post for this setting.
	 *
	 * Any created menu items will have their assigned post IDs exported to the client
	 * via the {@see 'customize_save_response'} filter. Likewise, any errors will be
	 * exported to the client via the customize_save_response() filter.
	 *
	 * To delete a menu, the client can send false as the value.
	 *
	 * @since 4.3.0
	 *
	 * @see wp_update_nav_menu_item()
	 *
	 * @param array|false $value The menu item array to update. If false, then the menu item will be deleted
	 *                           entirely. See WP_Customize_Nav_Menu_Item_Setting::$default for what the value
	 *                           should consist of.
	 * @return null|void
	 */
	protected function update( $value ) {
		if ( $this->is_updated ) {
			return;
		}

$this->is_updated = true;
		$is_placeholder   = ( $this->post_id < 0 );
		$is_delete        = ( false === $value );

// Update the cached value.
		$this->value = $value;

add_filter( 'customize_save_response', array( $this, 'amend_customize_save_response' ) );

if ( $is_delete ) {
			// If the current setting post is a placeholder, a delete request is a no-op.
			if ( $is_placeholder ) {
				$this->update_status = 'deleted';
			} else {
				$r = wp_delete_post( $this->post_id, true );

if ( false === $r ) {
					$this->update_error  = new WP_Error( 'delete_failure' );
					$this->update_status = 'error';
				} else {
					$this->update_status = 'deleted';
				}
				// @todo send back the IDs for all associated nav menu items deleted, so these settings (and controls) can be removed from Customizer?
			}
		} else {

// Handle saving menu items for menus that are being newly-created.
			if ( $value['nav_menu_term_id'] < 0 ) {
				$nav_menu_setting_id = sprintf( 'nav_menu[%s]', $value['nav_menu_term_id'] );
				$nav_menu_setting    = $this->manager->get_setting( $nav_menu_setting_id );

if ( ! $nav_menu_setting || ! ( $nav_menu_setting instanceof WP_Customize_Nav_Menu_Setting ) ) {
					$this->update_status = 'error';
					$this->update_error  = new WP_Error( 'unexpected_nav_menu_setting' );
					return;
				}

if ( false === $nav_menu_setting->save() ) {
					$this->update_status = 'error';
					$this->update_error  = new WP_Error( 'nav_menu_setting_failure' );
					return;
				}

if ( (int) $value['nav_menu_term_id'] !== $nav_menu_setting->previous_term_id ) {
					$this->update_status = 'error';
					$this->update_error  = new WP_Error( 'unexpected_previous_term_id' );
					return;
				}

$value['nav_menu_term_id'] = $nav_menu_setting->term_id;
			}

// Handle saving a nav menu item that is a child of a nav menu item being newly-created.
			if ( $value['menu_item_parent'] < 0 ) {
				$parent_nav_menu_item_setting_id = sprintf( 'nav_menu_item[%s]', $value['menu_item_parent'] );
				$parent_nav_menu_item_setting    = $this->manager->get_setting( $parent_nav_menu_item_setting_id );

if ( ! $parent_nav_menu_item_setting || ! ( $parent_nav_menu_item_setting instanceof WP_Customize_Nav_Menu_Item_Setting ) ) {
					$this->update_status = 'error';
					$this->update_error  = new WP_Error( 'unexpected_nav_menu_item_setting' );
					return;
				}

if ( false === $parent_nav_menu_item_setting->save() ) {
					$this->update_status = 'error';
					$this->update_error  = new WP_Error( 'nav_menu_item_setting_failure' );
					return;
				}

if ( (int) $value['menu_item_parent'] !== $parent_nav_menu_item_setting->previous_post_id ) {
					$this->update_status = 'error';
					$this->update_error  = new WP_Error( 'unexpected_previous_post_id' );
					return;
				}

$value['menu_item_parent'] = $parent_nav_menu_item_setting->post_id;
			}

// Insert or update menu.
			$menu_item_data = array(
				'menu-item-object-id'   => $value['object_id'],
				'menu-item-object'      => $value['object'],
				'menu-item-parent-id'   => $value['menu_item_parent'],
				'menu-item-position'    => $value['position'],
				'menu-item-type'        => $value['type'],
				'menu-item-title'       => $value['title'],
				'menu-item-url'         => $value['url'],
				'menu-item-description' => $value['description'],
				'menu-item-attr-title'  => $value['attr_title'],
				'menu-item-target'      => $value['target'],
				'menu-item-classes'     => $value['classes'],
				'menu-item-xfn'         => $value['xfn'],
				'menu-item-status'      => $value['status'],
			);

$r = wp_update_nav_menu_item(
				$value['nav_menu_term_id'],
				$is_placeholder ? 0 : $this->post_id,
				wp_slash( $menu_item_data )
			);

if ( is_wp_error( $r ) ) {
				$this->update_status = 'error';
				$this->update_error  = $r;
			} else {
				if ( $is_placeholder ) {
					$this->previous_post_id = $this->post_id;
					$this->post_id          = $r;
					$this->update_status    = 'inserted';
				} else {
					$this->update_status = 'updated';
				}
			}
		}
	}

/**
	 * Export data for the JS client.
	 *
	 * @since 4.3.0
	 *
	 * @see WP_Customize_Nav_Menu_Item_Setting::update()
	 *
	 * @param array $data Additional information passed back to the 'saved' event on `wp.customize`.
	 * @return array Save response data.
	 */
	public function amend_customize_save_response( $data ) {
		if ( ! isset( $data['nav_menu_item_updates'] ) ) {
			$data['nav_menu_item_updates'] = array();
		}

$data['nav_menu_item_updates'][] = array(
			'post_id'          => $this->post_id,
			'previous_post_id' => $this->previous_post_id,
			'error'            => $this->update_error ? $this->update_error->get_error_code() : null,
			'status'           => $this->update_status,
		);
		return $data;
	}
}

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Editing: class-wp-customize-nav-menu-item-setting.php

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