{WC} query products on sale trough GET

wc_loop_products_on_sale.php

<?php
add_filter('loop_shop_post_in', 'dk_filter_sale_products', 10);
add_filter('woocommerce_widget_get_current_page_url', 'dk_filter_links_with_sale', 10, 2);
function dk_filter_sale_products($array) {

    if(isset($_GET['akcija']) && $_GET['akcija']){
        $product_ids_on_sale = wc_get_product_ids_on_sale();
        $array = array_merge($array, $product_ids_on_sale);
    }

    return $array;
}
function dk_filter_links_with_sale ($link, $widget) {

    if(isset($_GET['akcija']) && $_GET['akcija']) {
        $link = add_query_arg( 'akcija', '1', $link );
    }

    return $link;
}