add_filter( 'nav_menu_link_attributes', 'filter_nav_menu_link_attributes', 10, 4 );
function filter_nav_menu_link_attributes( $atts, $item, $args, $depth ) {
$atts['class'] = 'header-nav__item';
if ( $item->current ) {
$atts['class'] .= ' header-nav__item_active';
}
return $atts;
}