Magento2: обновление строки кода в основном файле

Чтобы настроить основной файл Magento, вы можете использовать Preference или Plugin. Более подробно здесь

В вашем случае вы можете использовать предпочтения в качестве следующих шагов:

1. В di.xml вы можете добавить справочный конфиг:

<preference for="Magento\SalesRule\Model\Rule\Action\Discount\CartFixed" type="Training\Test\Model\Rule\Action\Discount\CartFixed" />


2. Создать Обучение \ Тест \ Модель \ Правило \ Действие \ Скидка \ CartFixed.php:

   • @author Бах Ли
     * /

   Тренировка пространства имен \ Test \ Model \ Rule \ Action \ Discount;

   использовать Magento \ Framework \ App \ ObjectManager;
   использовать Magento \ Framework \ Pricing \ PriceCurrencyInterface;
   use Magento \ SalesRule \ Model \ DeltaPriceRound;
   использовать Magento \ SalesRule \ Model \ Validator;
   использовать Magento \ SalesRule \ Model \ Rule \ Action \ DiscountFactory;

   класс CartFixed extends \ Magento \ SalesRule \ Model \ Rule \ Action \ Discount \ CartFixed
   {
   / **
   * строка @var
   * /
   private static $ discountType = ‘CartFixed’;
   / **
   * @var DeltaPriceRound
   * /
   private $ deltaPriceRound;

   /**
   * @param Validator $validator
   * @param DataFactory $discountDataFactory
   * @param PriceCurrencyInterface $priceCurrency
   * @param DeltaPriceRound $deltaPriceRound
   */
   public function __construct(
   Validator $validator,
   DataFactory $discountDataFactory,
   PriceCurrencyInterface $priceCurrency,
   DeltaPriceRound $deltaPriceRound = null
   ) {
   $this->deltaPriceRound = $deltaPriceRound ?: ObjectManager::getInstance()->get(DeltaPriceRound::class);
   
   parent::__construct($validator, $discountDataFactory, $priceCurrency, $deltaPriceRound);
   }
   
   /**
   * @param \Magento\SalesRule\Model\Rule $rule
   * @param \Magento\Quote\Model\Quote\Item\AbstractItem $item
   * @param float $qty
   * @return \Magento\SalesRule\Model\Rule\Action\Discount\Data
   * @throws \Magento\Framework\Exception\LocalizedException
   */
   public function calculate($rule, $item, $qty)
   {
   /** @var \Magento\SalesRule\Model\Rule\Action\Discount\Data $discountData */
   $discountData = $this->discountFactory->create();
   
   $ruleTotals = $this->validator->getRuleItemTotalsInfo($rule->getId());
   
   $quote = $item->getQuote();
   $address = $item->getAddress();
   
   $itemPrice = $this->validator->getItemPrice($item);
   $baseItemPrice = $this->validator->getItemBasePrice($item);
   $itemOriginalPrice = $this->validator->getItemOriginalPrice($item);
   $baseItemOriginalPrice = $this->validator->getItemBaseOriginalPrice($item);
   
   /**
   * prevent applying whole cart discount for every shipping order, but only for first order
   */
   if ($quote->getIsMultiShipping()) {
   $usedForAddressId = $this->getCartFixedRuleUsedForAddress($rule->getId());
   if ($usedForAddressId && $usedForAddressId != $address->getId()) {
   return $discountData;
   } else {
   $this->setCartFixedRuleUsedForAddress($rule->getId(), $address->getId());
   }
   }
   $cartRules = $address->getCartFixedRules();
   if (!isset($cartRules[$rule->getId()])) {
   $cartRules[$rule->getId()] = $rule->getDiscountAmount();
   }
   
   $availableDiscountAmount = (float)$cartRules[$rule->getId()];
   $discountType = self::$discountType . $rule->getId();
   
   $store = $quote->getStore();
   if ($ruleTotals['items_count'] <= 1) {
   $quoteAmount = $this->priceCurrency->convert($availableDiscountAmount, $store);
   $baseDiscountAmount = min($baseItemPrice * $qty, $availableDiscountAmount);
   $this->deltaPriceRound->reset($discountType);
   } else {
   $ratio = $baseItemPrice * $qty / $ruleTotals['base_items_price'];
   $maximumItemDiscount = $this->deltaPriceRound->round(
   $rule->getDiscountAmount() * $ratio,
   $discountType
   );
   
   $quoteAmount = $this->priceCurrency->convert($maximumItemDiscount, $store);
   
   $baseDiscountAmount = min($baseItemPrice * $qty, $maximumItemDiscount);
   $this->validator->decrementRuleItemTotalsCount($rule->getId());
   }
   
   $baseDiscountAmount = $this->priceCurrency->round($baseDiscountAmount);
   
   $availableDiscountAmount -= $baseDiscountAmount;
   $cartRules[$rule->getId()] = $availableDiscountAmount;
   if ($availableDiscountAmount <= 0) {
   $this->deltaPriceRound->reset($discountType);
   }
   
   $discountData->setAmount($this->priceCurrency->round(min($itemPrice * $qty, $quoteAmount)));
   $discountData->setBaseAmount($baseDiscountAmount);
   $discountData->setOriginalAmount(min($itemOriginalPrice * $qty, $quoteAmount));
   $discountData->setBaseOriginalAmount($this->priceCurrency->round($baseItemOriginalPrice));
   $address->setCartFixedRules($cartRules);
   
   return $discountData;
   }
   

   }

Или вы можете использовать cweagans / композитор-пластыри следующий этот вопрос редактировать основные файлы Magento

С уважением