$menu_item The menu item object.
	 */
	return apply_filters( 'wp_setup_nav_menu_item', $menu_item );
}

/**
 * Returns 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 );
	}
}

/**
 * Deletes 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' );
}

/**
 * Handles 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;
}