rm_id for categories.
 * - post_parent:      The DB ID of the original object's parent object, if any (0 otherwise).
 * - post_title:       A "no title" label if menu item represents a post that lacks a title.
 * - target:           The target attribute of the link element for this menu item.
 * - title:            The title of this menu item.
 * - type:             The family of objects originally represented, such as 'post_type' or 'taxonomy'.
 * - type_label:       The singular label used to describe this type of menu item.
 * - url:              The URL to which this menu item points.
 * - xfn:              The XFN relationship expressed in the link of this menu item.
 * - _invalid:         Whether the menu item represents an object that no longer exists.
 *
 * @since 3.0.0
 *
 * @param object $menu_item The menu item to modify.
 * @return object The menu item with standard menu item properties.
 */
function wp_setup_nav_menu_item( $menu_item ) {
	if ( isset( $menu_item->post_type ) ) {
		if ( 'nav_menu_item' === $menu_item->post_type ) {
			$menu_item->db_id            = (int) $menu_item->ID;
			$menu_item->menu_item_parent = ! isset( $menu_item->menu_item_parent ) ? get_post_meta( $menu_item->ID, '_menu_item_menu_item_parent', true ) : $menu_item->menu_item_parent;
			$menu_item->object_id        = ! isset( $menu_item->object_id ) ? get_post_meta( $menu_item->ID, '_menu_item_object_id', true ) : $menu_item->object_id;
			$menu_item->object           = ! isset( $menu_item->object ) ? get_post_meta( $menu_item->ID, '_menu_item_object', true ) : $menu_item->object;
			$menu_item->type             = ! isset( $menu_item->type ) ? get_post_meta( $menu_item->ID, '_menu_item_type', true ) : $menu_item->type;

			if ( 'post_type' === $menu_item->type ) {
				$object = get_post_type_object( $menu_item->object );
				if ( $object ) {
					$menu_item->type_label = $object->labels->singular_name;
					// Denote post states for special pages (only in the admin).
					if ( function_exists( 'get_post_states' ) ) {
						$menu_post   = get_post( $menu_item->object_id );
						$post_states = get_post_states( $menu_post );
						if ( $post_states ) {
							$menu_item->type_label = wp_strip_all_tags( implode( ', ', $post_states ) );
						}
					}
				} else {
					$menu_item->type_label = $menu_item->object;
					$menu_item->_invalid   = true;
				}

				if ( 'trash' === get_post_status( $menu_item->object_id ) ) {
					$menu_item->_invalid = true;
				}

				$original_object = get_post( $menu_item->object_id );

				if ( $original_object ) {
					$menu_item->url = get_permalink( $original_object->ID );
					/** This filter is documented in wp-includes/post-template.php */
					$original_title = apply_filters( 'the_title', $original_object->post_title, $original_object->ID );
				} else {
					$menu_item->url      = '';
					$original_title      = '';
					$menu_item->_invalid = true;
				}

				if ( '' === $original_title ) {
					/* translators: %d: ID of a post. */
					$original_title = sprintf( __( '#%d (no title)' ), $menu_item->object_id );
				}

				$menu_item->title = ( '' === $menu_item->post_title ) ? $original_title : $menu_item->post_title;

			} elseif ( 'post_type_archive' === $menu_item->type ) {
				$object = get_post_type_object( $menu_item->object );
				if ( $object ) {
					$menu_item->title      = ( '' === $menu_item->post_title ) ? $object->labels->archives : $menu_item->post_title;
					$post_type_description = $object->description;
				} else {
					$post_type_description = '';
					$menu_item->_invalid   = true;
				}

				$menu_item->type_label = __( 'Post Type Archive' );
				$post_content          = wp_trim_words( $menu_item->post_content, 200 );
				$post_type_description = ( '' === $post_content ) ? $post_type_description : $post_content;
				$menu_item->url        = get_post_type_archive_link( $menu_item->object );

			} elseif ( 'taxonomy' === $menu_item->type ) {
				$object = get_taxonomy( $menu_item->object );
				if ( $object ) {
					$menu_item->type_label = $object->labels->singular_name;
				} else {
					$menu_item->type_label = $menu_item->object;
					$menu_item->_invalid   = true;
				}

				$original_object = get_term( (int) $menu_item->object_id, $menu_item->object );

				if ( $original_object && ! is_wp_error( $original_object ) ) {
					$menu_item->url = get_term_link( (int) $menu_item->object_id, $menu_item->object );
					$original_title = $original_object->name;
				} else {
					$menu_item->url      = '';
					$original_title      = '';
					$menu_item->_invalid = true;
				}

				if ( '' === $original_title ) {
					/* translators: %d: ID of a term. */
					$original_title = sprintf( __( '#%d (no title)' ), $menu_item->object_id );
				}

				$menu_item->title = ( '' === $menu_item->post_title ) ? $original_title : $menu_item->post_title;

			} else {
				$menu_item->type_label = __( 'Custom Link' );
				$menu_item->title      = $menu_item->post_title;
				$menu_item->url        = ! isset( $menu_item->url ) ? get_post_meta( $menu_item->ID, '_menu_item_url', true ) : $menu_item->url;
			}

			$menu_item->target = ! isset( $menu_item->target ) ? get_post_meta( $menu_item->ID, '_menu_item_target', true ) : $menu_item->target;

			/**
			 * Filters a navigation menu item's title attribute.
			 *
			 * @since 3.0.0
			 *
			 * @param string $item_title The menu item title attribute.
			 */
			$menu_item->attr_title = ! isset( $menu_item->attr_title ) ? apply_filters( 'nav_menu_attr_title', $menu_item->post_excerpt ) : $menu_item->attr_title;

			if ( ! isset( $menu_item->description ) ) {
				/**
				 * Filters a navigation menu item's description.
				 *
				 * @since 3.0.0
				 *
				 * @param string $description The menu item description.
				 */
				$menu_item->description = apply_filters( 'nav_menu_description', wp_trim_words( $menu_item->post_content, 200 ) );
			}

			$menu_item->classes = ! isset( $menu_item->classes ) ? (array) get_post_meta( $menu_item->ID, '_menu_item_classes', true ) : $menu_item->classes;
			$menu_item->xfn     = ! isset( $menu_item->xfn ) ? get_post_meta( $menu_item->ID, '_menu_item_xfn', true ) : $menu_item->xfn;
		} else {
			$menu_item->db_id            = 0;
			$menu_item->menu_item_parent = 0;
			$menu_item->object_id        = (int) $menu_item->ID;
			$menu_item->type             = 'post_type';

			$object                = get_post_type_object( $menu_item->post_type );
			$menu_item->object     = $object->name;
			$menu_item->type_label = $object->labels->singular_name;

			if ( '' === $menu_item->post_title ) {
				/* translators: %d: ID of a post. */
				$menu_item->post_title = sprintf( __( '#%d (no title)' ), $menu_item->ID );
			}

			$menu_item->title  = $menu_item->post_title;
			$menu_item->url    = get_permalink( $menu_item->ID );
			$menu_item->target = '';

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

			/** This filter is documented in wp-includes/nav-menu.php */
			$menu_item->description = apply_filters( 'nav_menu_description', '' );
			$menu_item->classes     = array();
			$menu_item->xfn         = '';
		}
	} elseif ( isset( $menu_item->taxonomy ) ) {
		$menu_item->ID               = $menu_item->term_id;
		$menu_item->db_id            = 0;
		$menu_item->menu_item_parent = 0;
		$menu_item->object_id        = (int) $menu_item->term_id;
		$menu_item->post_parent      = (int) $menu_item->parent;
		$menu_item->type             = 'taxonomy';

		$object                = get_taxonomy( $menu_item->taxonomy );
		$menu_item->object     = $object->name;
		$menu_item->type_label = $object->labels->singular_name;

		$menu_item->title       = $menu_item->name;
		$menu_item->url         = get_term_link( $menu_item, $menu_item->taxonomy );
		$menu_item->target      = '';
		$menu_item->attr_title  = '';
		$menu_item->description = get_term_field( 'description', $menu_item->term_id, $menu_item->taxonomy );
		$menu_item->classes     = array();
		$menu_item->xfn         = '';

	}

	/**
	 * Filters a navigation menu item object.
	 *
	 * @since 3.0.0
	 *
	 * @param object $menu_item The menu item object.
	 */
	return apply_filters( 'wp_setup_nav_menu_item', $menu_item );
}

/**
 * Get the menu items associated with a particular object.
 *
 * @since 3.0.0
 *
 * @param int    $object_id   Optional. The ID of the original object. Default 0.
 * @param string $object_type Optional. The type of object, such as 'post_type' or 'taxonomy'.
 *                            Default 'post_type'.
 * @param string $taxonomy    Optional. If $object_type is 'taxonomy', $taxonomy is the name
 *                            of the tax that $object_id belongs to. Default empty.
 * @return int[] The array of menu item IDs; empty array if none.
 */
function wp_get_associated_nav_menu_items( $object_id = 0, $object_type = 'post_type', $taxonomy = '' ) {
	$object_id     = (int) $object_id;
	$menu_item_ids = array();

	$query      = new WP_Query;
	$menu_items = $query->query(
		array(
			'meta_key'       => '_menu_item_object_id',
			'meta_value'     => $object_id,
			'post_status'    => 'any',
			'post_type'      => 'nav_menu_item',
			'posts_per_page' => -1,
		)
	);
	foreach ( (array) $menu_items as $menu_item ) {
		if ( isset( $menu_item->ID ) && is_nav_menu_item( $menu_item->ID ) ) {
			$menu_item_type = get_post_meta( $menu_item->ID, '_menu_item_type', true );
			if (
				'post_type' === $object_type &&
				'post_type' === $menu_item_type
			) {
				$menu_item_ids[] = (int) $menu_item->ID;
			} elseif (
				'taxonomy' === $object_type &&
				'taxonomy' === $menu_item_type &&
				get_post_meta( $menu_item->ID, '_menu_item_object', true ) == $taxonomy
			) {
				$menu_item_ids[] = (int) $menu_item->ID;
			}
		}
	}

	return array_unique( $menu_item_ids );
}

/**
 * Callback for handling a menu item when its original object is deleted.
 *
 * @since 3.0.0
 * @access private
 *
 * @param int $object_id The ID of the original object being trashed.
 */
function _wp_delete_post_menu_item( $object_id ) {
	$object_id = (int) $object_id;

	$menu_item_ids = wp_get_associated_nav_menu_items( $object_id, 'post_type' );

	foreach ( (array) $menu_item_ids as $menu_item_id ) {
		wp_delete_post( $menu_item_id, true );
	}
}

/**
 * Serves as a callback for handling a menu item when its original object is deleted.
 *
 * @since 3.0.0
 * @access private
 *
 * @param int    $object_id The ID of the original object being trashed.
 * @param int    $tt_id     Term taxonomy ID. Unused.
 * @param string $taxonomy  Taxonomy slug.
 */
function _wp_delete_tax_menu_item( $object_id, $tt_id, $taxonomy ) {
	$object_id = (int) $object_id;

	$menu_item_ids = wp_get_associated_nav_menu_items( $object_id, 'taxonomy', $taxonomy );

	foreach ( (array) $menu_item_ids as $menu_item_id ) {
		wp_delete_post( $menu_item_id, true );
	}
}

/**
 * Automatically add newly published page objects to menus with that as an option.
 *
 * @since 3.0.0
 * @access private
 *
 * @param string  $new_status The new status of the post object.
 * @param string  $old_status The old status of the post object.
 * @param WP_Post $post       The post object being transitioned from one status to another.
 */
function _wp_auto_add_pages_to_menu( $new_status, $old_status, $post ) {
	if ( 'publish' !== $new_status || 'publish' === $old_status || 'page' !== $post->post_type ) {
		return;
	}
	if ( ! empty( $post->post_parent ) ) {
		return;
	}
	$auto_add = get_option( 'nav_menu_options' );
	if ( empty( $auto_add ) || ! is_array( $auto_add ) || ! isset( $auto_add['auto_add'] ) ) {
		return;
	}
	$auto_add = $auto_add['auto_add'];
	if ( empty( $auto_add ) || ! is_array( $auto_add ) ) {
		return;
	}

	$args = array(
		'menu-item-object-id' => $post->ID,
		'menu-item-object'    => $post->post_type,
		'menu-item-type'      => 'post_type',
		'menu-item-status'    => 'publish',
	);

	foreach ( $auto_add as $menu_id ) {
		$items = wp_get_nav_menu_items( $menu_id, array( 'post_status' => 'publish,draft' ) );
		if ( ! is_array( $items ) ) {
			continue;
		}
		foreach ( $items as $item ) {
			if ( $post->ID == $item->object_id ) {
				continue 2;
			}
		}
		wp_update_nav_menu_item( $menu_id, 0, $args );
	}
}

/**
 * Delete auto-draft posts associated with the supplied changeset.
 *
 * @since 4.8.0
 * @access private
 *
 * @param int $post_id Post ID for the customize_changeset.
 */
function _wp_delete_customize_changeset_dependent_auto_drafts( $post_id ) {
	$post = get_post( $post_id );

	if ( ! $post || 'customize_changeset' !== $post->post_type ) {
		return;
	}

	$data = json_decode( $post->post_content, true );
	if ( empty( $data['nav_menus_created_posts']['value'] ) ) {
		return;
	}
	remove_action( 'delete_post', '_wp_delete_customize_changeset_dependent_auto_drafts' );
	foreach ( $data['nav_menus_created_posts']['value'] as $stub_post_id ) {
		if ( empty( $stub_post_id ) ) {
			continue;
		}
		if ( 'auto-draft' === get_post_status( $stub_post_id ) ) {
			wp_delete_post( $stub_post_id, true );
		} elseif ( 'draft' === get_post_status( $stub_post_id ) ) {
			wp_trash_post( $stub_post_id );
			delete_post_meta( $stub_post_id, '_customize_changeset_uuid' );
		}
	}
	add_action( 'delete_post', '_wp_delete_customize_changeset_dependent_auto_drafts' );
}

/**
 * Handle menu config after theme change.
 *
 * @access private
 * @since 4.9.0
 */
function _wp_menus_changed() {
	$old_nav_menu_locations    = get_option( 'theme_switch_menu_locations', array() );
	$new_nav_menu_locations    = get_nav_menu_locations();
	$mapped_nav_menu_locations = wp_map_nav_menu_locations( $new_nav_menu_locations, $old_nav_menu_locations );

	set_theme_mod( 'nav_menu_locations', $mapped_nav_menu_locations );
	delete_option( 'theme_switch_menu_locations' );
}

/**
 * Maps nav menu locations according to assignments in previously active theme.
 *
 * @since 4.9.0
 *
 * @param array $new_nav_menu_locations New nav menu locations assignments.
 * @param array $old_nav_menu_locations Old nav menu locations assignments.
 * @return array Nav menus mapped to new nav menu locations.
 */
function wp_map_nav_menu_locations( $new_nav_menu_locations, $old_nav_menu_locations ) {
	$registered_nav_menus   = get_registered_nav_menus();
	$new_nav_menu_locations = array_intersect_key( $new_nav_menu_locations, $registered_nav_menus );

	// Short-circuit if there are no old nav menu location assignments to map.
	if ( empty( $old_nav_menu_locations ) ) {
		return $new_nav_menu_locations;
	}

	// If old and new theme have just one location, map it and we're done.
	if ( 1 === count( $old_nav_menu_locations ) && 1 === count( $registered_nav_menus ) ) {
		$new_nav_menu_locations[ key( $registered_nav_menus ) ] = array_pop( $old_nav_menu_locations );
		return $new_nav_menu_locations;
	}

	$old_locations = array_keys( $old_nav_menu_locations );

	// Map locations with the same slug.
	foreach ( $registered_nav_menus as $location => $name ) {
		if ( in_array( $location, $old_locations, true ) ) {
			$new_nav_menu_locations[ $location ] = $old_nav_menu_locations[ $location ];
			unset( $old_nav_menu_locations[ $location ] );
		}
	}

	// If there are no old nav menu locations left, then we're done.
	if ( empty( $old_nav_menu_locations ) ) {
		return $new_nav_menu_locations;
	}

	/*
	 * If old and new theme both have locations that contain phrases
	 * from within the same group, make an educated guess and map it.
	 */
	$common_slug_groups = array(
		array( 'primary', 'menu-1', 'main', 'header', 'navigation', 'top' ),
		array( 'secondary', 'menu-2', 'footer', 'subsidiary', 'bottom' ),
		array( 'social' ),
	);

	// Go through each group...
	foreach ( $common_slug_groups as $slug_group ) {

		// ...and see if any of these slugs...
		foreach ( $slug_group as $slug ) {

			// ...and any of the new menu locations...
			foreach ( $registered_nav_menus as $new_location => $name ) {

				// ...actually match!
				if ( is_string( $new_location ) && false === stripos( $new_location, $slug ) && false === stripos( $slug, $new_location ) ) {
					continue;
				} elseif ( is_numeric( $new_location ) && $new_location !== $slug ) {
					continue;
				}

				// Then see if any of the old locations...
				foreach ( $old_nav_menu_locations as $location => $menu_id ) {

					// ...and any slug in the same group...
					foreach ( $slug_group as $slug ) {

						// ... have a match as well.
						if ( is_string( $location ) && false === stripos( $location, $slug ) && false === stripos( $slug, $location ) ) {
							continue;
						} elseif ( is_numeric( $location ) && $location !== $slug ) {
							continue;
						}

						// Make sure this location wasn't mapped and removed previously.
						if ( ! empty( $old_nav_menu_locations[ $location ] ) ) {

							// We have a match that can be mapped!
							$new_nav_menu_locations[ $new_location ] = $old_nav_menu_locations[ $location ];

							// Remove the mapped location so it can't be mapped again.
							unset( $old_nav_menu_locations[ $location ] );

							// Go back and check the next new menu location.
							continue 3;
						}
					} // End foreach ( $slug_group as $slug ).
				} // End foreach ( $old_nav_menu_locations as $location => $menu_id ).
			} // End foreach foreach ( $registered_nav_menus as $new_location => $name ).
		} // End foreach ( $slug_group as $slug ).
	} // End foreach ( $common_slug_groups as $slug_group ).

	return $new_nav_menu_locations;
}