Drupal 8 Use "menu-item--active-trail" to set active class in menu

Code snippet that can be used to set active class in menu using "menu-item--active-trail"  in Drupal 8.

/**
 * Implements hook_preprocess_menu() for menu.html.twig.
 */
function themename_preprocess_menu(&$variables, $hook) {
    if ($hook == 'menu') {
        $current_path = \Drupal::request()->getRequestUri();
        foreach ($variables['items'] as &$item) {
            if ($item['in_active_trail']) {
                if ($item['url']->toString() == $current_path) {
                    $item['is_active'] = TRUE;
                } elseif (count($item['below'])) {
                    _themename_menu_process_submenu($item['below'], $current_path);
                }
            }
        }
    }
}

/**
 * Set active and active-trail class for sub-menus recursively.
 */
function _themename_menu_process_submenu(&$submenu, $current_path) {
    foreach ($submenu as &$item) {
        if ($item['in_active_trail']) {
            if ($item['url']->toString() == $current_path) {
                $item['is_active'] = TRUE;
            } elseif (count($item['below'])) {
                _themename_menu_process_submenu($item['below'], $current_path);
            }
        }
    }
}

and in twig file menu--main.html.twig just use:

{%
    set item_classes = [
        'menu',
        item.in_active_trail ? 'active-trail',
          item.is_active ? 'active',
        ]
    %}