Source

File: wp-includes/nav-menu.php

function wp_update_nav_menu_object( $menu_id = 0, $menu_data = array() ) {
	// expected_slashed ($menu_data)
	$menu_id = (int) $menu_id;

	$_menu = wp_get_nav_menu_object( $menu_id );

	$args = array(
		'description' => ( isset( $menu_data['description'] ) ? $menu_data['description'] : '' ),
		'name'        => ( isset( $menu_data['menu-name'] ) ? $menu_data['menu-name'] : '' ),
		'parent'      => ( isset( $menu_data['parent'] ) ? (int) $menu_data['parent'] : 0 ),
		'slug'        => null,
	);

	// Double-check that we're not going to have one menu take the name of another.
	$_possible_existing = get_term_by( 'name', $menu_data['menu-name'], 'nav_menu' );
	if (
		$_possible_existing &&
		! is_wp_error( $_possible_existing ) &&
		isset( $_possible_existing->term_id ) &&
		$_possible_existing->term_id != $menu_id
	) {
		return new WP_Error(
			'menu_exists',
			sprintf(
				/* translators: %s: Menu name. */
				__( 'The menu name %s conflicts with another menu name. Please try another.' ),
				'<strong>' . esc_html( $menu_data['menu-name'] ) . '</strong>'
			)
		);
	}

	// Menu doesn't already exist, so create a new menu.
	if ( ! $_menu || is_wp_error( $_menu ) ) {
		$menu_exists = get_term_by( 'name', $menu_data['menu-name'], 'nav_menu' );

		if ( $menu_exists ) {
			return new WP_Error(
				'menu_exists',
				sprintf(
					/* translators: %s: Menu name. */
					__( 'The menu name %s conflicts with another menu name. Please try another.' ),
					'<strong>' . esc_html( $menu_data['menu-name'] ) . '</strong>'
				)
			);
		}

		$_menu = wp_insert_term( $menu_data['menu-name'], 'nav_menu', $args );

		if ( is_wp_error( $_menu ) ) {
			return $_menu;
		}

		/**
		 * Fires after a navigation menu is successfully created.
		 *
		 * @since 3.0.0
		 *
		 * @param int   $term_id   ID of the new menu.
		 * @param array $menu_data An array of menu data.
		 */
		do_action( 'wp_create_nav_menu', $_menu['term_id'], $menu_data );

		return (int) $_menu['term_id'];
	}

	if ( ! $_menu || ! isset( $_menu->term_id ) ) {
		return 0;
	}

	$menu_id = (int) $_menu->term_id;

	$update_response = wp_update_term( $menu_id, 'nav_menu', $args );

	if ( is_wp_error( $update_response ) ) {
		return $update_response;
	}

	$menu_id = (int) $update_response['term_id'];

	/**
	 * Fires after a navigation menu has been successfully updated.
	 *
	 * @since 3.0.0
	 *
	 * @param int   $menu_id   ID of the updated menu.
	 * @param array $menu_data An array of menu data.
	 */
	do_action( 'wp_update_nav_menu', $menu_id, $menu_data );
	return $menu_id;
}