.-.-.-.-.-

<?php
/**
 * @link https://craftcms.com/
 * @copyright Copyright (c) Pixel & Tonic, Inc.
 * @license https://craftcms.github.io/license/
 */

namespace craft\commerce\helpers;

use craft\commerce\elements\Order as OrderElement;

/**
 * Order helper
 *
 * @author Pixel & Tonic, Inc. <support@pixelandtonic.com>
 * @since 2.1
 */
class Order
{
    /**
     * @return bool Were any line items merged?
     */
    public static function mergeDuplicateLineItems(OrderElement $order): bool
    {
        $lineItems = $order->getLineItems();
        // Ensure no duplicate line items exist, and if they do, combine them.
        $lineItemsByKey = [];
        foreach ($lineItems as $lineItem) {
            $key = $lineItem->orderId . '-' . $lineItem->purchasableId . '-' . $lineItem->getOptionsSignature();
            if (isset($lineItemsByKey[$key])) {
                $lineItemsByKey[$key]->qty += $lineItem->qty;
                // If a note already exists, merge it.
                if ($lineItemsByKey[$key]->note && $lineItem->note) {
                    $lineItemsByKey[$key]->note .= ' - ' . $lineItem->note;
                } else {
                    $lineItemsByKey[$key]->note = $lineItem->note;
                }
            } else {
                $lineItemsByKey[$key] = $lineItem;
            }
        }

$order->setLineItems(array_values($lineItemsByKey));

return $lineItems > $lineItemsByKey;
    }
}

/srv/users/craft4/apps/craft4-newsite-space/vendor/craftcms/commerce/src/test/../helpers/Order.php