WC_Abstract_Legacy_Order::update_product PHP Method

    public function update_product($item, $product, $args)
    {
        wc_deprecated_function('WC_Order::update_product', '2.7', 'Interact with WC_Order_Item_Product class');
        if (is_numeric($item)) {
            $item = $this->get_item($item);
        }
        if (!is_object($item) || !$item->is_type('line_item')) {
            return false;
        }
        if (!$this->get_id()) {
            $this->save();
            // Order must exist
        }
        // BW compatibility with old args
        if (isset($args['totals'])) {
            foreach ($args['totals'] as $key => $value) {
                if ('tax' === $key) {
                    $args['total_tax'] = $value;
                } elseif ('tax_data' === $key) {
                    $args['taxes'] = $value;
                } else {
                    $args[$key] = $value;
                }
            }
        }
        // Handly qty if set
        if (isset($args['qty'])) {
            if ($product->backorders_require_notification() && $product->is_on_backorder($args['qty'])) {
                $item->add_meta_data(apply_filters('woocommerce_backordered_item_meta_name', __('Backordered', 'woocommerce')), $args['qty'] - max(0, $product->get_stock_quantity()), true);
            }
            $args['subtotal'] = $args['subtotal'] ? $args['subtotal'] : wc_get_price_excluding_tax($product, array('qty' => $args['qty']));
            $args['total'] = $args['total'] ? $args['total'] : wc_get_price_excluding_tax($product, array('qty' => $args['qty']));
        }
        $item->set_order_id($this->get_id());
        $item->set_props($args);
        $item->save();
        do_action('woocommerce_order_edit_product', $this->get_id(), $item->get_id(), $args, $product);
        return $item->get_id();
    }