// カートへ追加
$this->cartService->addProduct($addCartData['product_class_id'], $addCartData['quantity']);

// 明細の正規化
$Carts = $this->cartService->getCarts();
foreach ($Carts as $Cart) {
    $result = $this->purchaseFlow->validate($Cart, new PurchaseContext($Cart, $this->getUser()));
    // 復旧不可のエラーが発生した場合は追加した明細を削除.
    if ($result->hasError()) {
        $this->cartService->removeProduct($addCartData['product_class_id']);
        foreach ($result->getErrors() as $error) {
            $errorMessages[] = $error->getMessage();
        }
    }
    foreach ($result->getWarning() as $warning) {
        $errorMessages[] = $warning->getMessage();
    }
}

$this->cartService->save();