function wp_nav_menu( $args = array() ) {
  static $menu_id_slugs = array();

  $defaults = array(
    'menu'            => '',
    'container'       => 'div',
    'container_class' => '',
    'container_id'    => '',
    'menu_class'      => 'menu',
    'menu_id'         => '',
    'echo'            => true,
    'fallback_cb'     => 'wp_page_menu',
    'before'          => '',
    'after'           => '',
    'link_before'     => '',
    'link_after'      => '',
    'items_wrap'      => '<ul id="%1$s" class="%2$s">%3$s</ul>',
    'item_spacing'    => 'preserve',
    'depth'           => 0,
    'walker'          => '',
    'theme_location'  => '',
  );

  $args = wp_parse_args( $args, $defaults );

  if ( ! in_array( $args['item_spacing'], array( 'preserve', 'discard' ), true ) ) {
    // Invalid value, fall back to default.
    $args['item_spacing'] = $defaults['item_spacing'];
  }

  
/**
 * Filters the arguments used to display a navigation menu.
 *
 * @since 3.0.0
 *
 * @see wp_nav_menu()
 *
 * @param array $args Array of wp_nav_menu() arguments.
 */
  $args = apply_filters( 'wp_nav_menu_args', $args );
  $args = (object) $args;

  
/**
 * Filters whether to short-circuit the wp_nav_menu() output.
 *
 * Returning a non-null value to the filter will short-circuit
 * wp_nav_menu(), echoing that value if $args->echo is true,
 * returning that value otherwise.
 *
 * @since 3.9.0
 *
 * @see wp_nav_menu()
 *
 * @param string|null $output Nav menu output to short-circuit with. Default null.
 * @param stdClass    $args   An object containing wp_nav_menu() arguments.
 */
  $nav_menu = apply_filters( 'pre_wp_nav_menu', null, $args );

  if ( null !== $nav_menu ) {
    if ( $args->echo ) {
      echo $nav_menu;
      return;
    }

    return $nav_menu;
  }

  // Get the nav menu based on the requested menu.
  $menu = wp_get_nav_menu_object( $args->menu );

  // Get the nav menu based on the theme_location.
  $locations = get_nav_menu_locations();
  if ( ! $menu && $args->theme_location && $locations && isset( $locations[ $args->theme_location ] ) ) {
    $menu = wp_get_nav_menu_object( $locations[ $args->theme_location ] );
  }

  // Get the first menu that has items if we still can't find a menu.
  if ( ! $menu && ! $args->theme_location ) {
    $menus = wp_get_nav_menus();
    foreach ( $menus as $menu_maybe ) {
      $menu_items = wp_get_nav_menu_items( $menu_maybe->term_id, array( 'update_post_term_cache' => false ) );
      if ( $menu_items ) {
        $menu = $menu_maybe;
        break;
      }
    }
  }

  if ( empty( $args->menu ) ) {
    $args->menu = $menu;
  }

  // If the menu exists, get its items.
  if ( $menu && ! is_wp_error( $menu ) && ! isset( $menu_items ) ) {
    $menu_items = wp_get_nav_menu_items( $menu->term_id, array( 'update_post_term_cache' => false ) );
  }

  /*
	 * If no menu was found: