Woo sale badge display even with only one variation

woo-show-sale-badge-even-one-variation.php

<?php
add_filter('woocommerce_product_is_on_sale', function ($on_sale, $product) {
    if ($product->is_type('variable') && (is_shop() || is_product() || is_product_category() || is_product_tag())) {
        foreach ($product->get_children() as $variation_id) {
            $variation = wc_get_product($variation_id);
            if ($variation->is_on_sale()) {
                return true;
            }
        }
    }

    return $on_sale;
}, 10, 2);