Magento2.1.9 : Out of stock product Backorder not working?

Question

I have to used Magento2.1.9 when I add out of stock product to cart it is not working and am getting error as this product out of stock I need backorder working properly for out of stock product and I find, this is a bug in magento2.1.9 and applied patch after resolve issue but i am not getting patch file . So Ihave tried the other way override this file and add code below we are using.

\Magento\CatalogInventory\Model\Quote\Item\QuantityValidator\QuantityValidator.php

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
<preference for="Magento\CatalogInventory\Model\Quote\Item\QuantityValidator" type="XXXX\XXXX\Model\Quote\Item\QuantityValidator" />
</config>

this is my code used QuantityValidator.php

    <?php
    namespace XXXXX\XXXXX\Model\Quote\Item;

    use Magento\CatalogInventory\Model\Stock;

    /**
     * Quantity validation.
     */
    class QuantityValidator extends \Magento\CatalogInventory\Model\Quote\Item\QuantityValidator
    {
         protected $optionInitializer;

        /**
         * @var QuantityValidator\Initializer\StockItem
         */
        protected $stockItemInitializer;

        /**
         * Stock registry.
         *
         * @var \Magento\CatalogInventory\Api\StockRegistryInterface
         */
        protected $stockRegistry;

        /**
         * Stock state.
         *
         * @var \Magento\CatalogInventory\Api\StockStateInterface
         */
        protected $stockState;

        /**
         * @param QuantityValidator\Initializer\Option $optionInitializer
         * @param QuantityValidator\Initializer\StockItem $stockItemInitializer
         * @param \Magento\CatalogInventory\Api\StockRegistryInterface $stockRegistry
         * @param \Magento\CatalogInventory\Api\StockStateInterface $stockState
         */
        public function __construct(
            QuantityValidator\Initializer\Option $optionInitializer,
            QuantityValidator\Initializer\StockItem $stockItemInitializer,
            \Magento\CatalogInventory\Api\StockRegistryInterface $stockRegistry,
            \Magento\CatalogInventory\Api\StockStateInterface $stockState
        ) {


$this->optionInitializer = $optionInitializer;
        $this->stockItemInitializer = $stockItemInitializer;
        $this->stockRegistry = $stockRegistry;
        $this->stockState = $stockState;
    }

    /**
     * Check product inventory data when quote item quantity declaring
     *
     * @param \Magento\Framework\Event\Observer $observer
     *
     * @return void
     * @throws \Magento\Framework\Exception\LocalizedException
     * @SuppressWarnings(PHPMD.CyclomaticComplexity)
     * @SuppressWarnings(PHPMD.NPathComplexity)
     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
     */
    public function validate(\Magento\Framework\Event\Observer $observer)
    {
        /* @var $quoteItem \Magento\Quote\Model\Quote\Item */
        $quoteItem = $observer->getEvent()->getItem();
        if (!$quoteItem ||
            !$quoteItem->getProductId() ||
            !$quoteItem->getQuote() ||
            $quoteItem->getQuote()->getIsSuperMode()
        ) {
            return;
        }
        $product = $quoteItem->getProduct();
        $qty = $quoteItem->getQty();

        /** @var \Magento\CatalogInventory\Model\Stock\Item $stockItem */
        $stockItem = $this->stockRegistry->getStockItem(
            $quoteItem->getProduct()->getId(),
            $quoteItem->getProduct()->getStore()->getWebsiteId()
        );

        if (!$stockItem instanceof \Magento\CatalogInventory\Api\Data\StockItemInterface) {
            throw new \Magento\Framework\Exception\LocalizedException(__('The stock item for Product is not valid.'));
        }

        /** @var \Magento\CatalogInventory\Api\Data\StockStatusInterface $stockStatus */
        $stockStatus = $this->stockRegistry->getStockStatus($product->getId(), $product->getStore()->getWebsiteId());

        /** @var \Magento\CatalogInventory\Api\Data\StockStatusInterface|bool $parentStockStatus */
        $parentStockStatus = false;

        /**
         * Check if product in stock. For composite products check base (parent) item stock status
         */
        if ($quoteItem->getParentItem()) {
            $product = $quoteItem->getParentItem()->getProduct();
            $parentStockStatus = $this->stockRegistry->getStockStatus(
                $product->getId(),
                $product->getStore()->getWebsiteId()
            );
        }

        if ($stockStatus) {
            if (($stockStatus->getStockStatus() == Stock::STOCK_OUT_OF_STOCK
               || $parentStockStatus && $parentStockStatus->getStockStatus() == Stock::STOCK_OUT_OF_STOCK) && !$stockItem->getBackorders()
             ) {
                $quoteItem->addErrorInfo(
                    'cataloginventory',
                    \Magento\CatalogInventory\Helper\Data::ERROR_QTY,
                    __('This product is out of stock.')
                );
                $quoteItem->getQuote()->addErrorInfo(
                    'stock',
                    'cataloginventory',
                    \Magento\CatalogInventory\Helper\Data::ERROR_QTY,
                    __('Some of the products are out of stock.')
                );
                return;
            } else {
                // Delete error from item and its quote, if it was set due to item out of stock
                $this->_removeErrorsFromQuoteAndItem($quoteItem, \Magento\CatalogInventory\Helper\Data::ERROR_QTY);
            }
        }
    }
}
?>

after override this file in our module getting this

ReflectionException                                                                                                                                                               
  Class XXXX\XXXX\Model\Quote\Item\QuantityValidator\Initializer\Option does not exist  

if anyone know reply me

Answer 1

Problem in your __construct. Try the following way:

public function __construct(
    \Magento\CatalogInventory\Model\Quote\Item\QuantityValidator\Initializer\Option $optionInitializer,
    \Magento\CatalogInventory\Model\Quote\Item\QuantityValidator\Initializer\StockItem $stockItemInitializer,
    \Magento\CatalogInventory\Api\StockRegistryInterface $stockRegistry,
    \Magento\CatalogInventory\Api\StockStateInterface $stockState
) {

Answer 2

It's working code here

add in your custom module di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
<preference for="Magento\CatalogInventory\Model\Quote\Item\QuantityValidator" type="XXXXX\XXXXXX\Model\Quote\Item\QuantityValidator" />
</config>

add in you custom module inside model file app/code/Namespace/Modulname/Model/Quote/Item/QuantityValidator.php

<?php
namespace XXXXXX\XXXXXX\Model\Quote\Item;

use Magento\CatalogInventory\Model\Stock;

/**
 * Quantity validation.
 */
class QuantityValidator extends \Magento\CatalogInventory\Model\Quote\Item\QuantityValidator
{
     protected $optionInitializer;

    /**
     * @var QuantityValidator\Initializer\StockItem
     */
    protected $stockItemInitializer;

    /**
     * Stock registry.
     *
     * @var \Magento\CatalogInventory\Api\StockRegistryInterface
     */
    protected $stockRegistry;

    /**
     * Stock state.
     *
     * @var \Magento\CatalogInventory\Api\StockStateInterface
     */
    protected $stockState;

    /**
     * @param QuantityValidator\Initializer\Option $optionInitializer
     * @param QuantityValidator\Initializer\StockItem $stockItemInitializer
     * @param \Magento\CatalogInventory\Api\StockRegistryInterface $stockRegistry
     * @param \Magento\CatalogInventory\Api\StockStateInterface $stockState
     */
    public function __construct(
    \Magento\CatalogInventory\Model\Quote\Item\QuantityValidator\Initializer\Option $optionInitializer,
    \Magento\CatalogInventory\Model\Quote\Item\QuantityValidator\Initializer\StockItem $stockItemInitializer,
    \Magento\CatalogInventory\Api\StockRegistryInterface $stockRegistry,
    \Magento\CatalogInventory\Api\StockStateInterface $stockState
) {
        $this->optionInitializer = $optionInitializer;
        $this->stockItemInitializer = $stockItemInitializer;
        $this->stockRegistry = $stockRegistry;
        $this->stockState = $stockState;
    }

    /**
     * Check product inventory data when quote item quantity declaring
     *
     * @param \Magento\Framework\Event\Observer $observer
     *
     * @return void
     * @throws \Magento\Framework\Exception\LocalizedException
     * @SuppressWarnings(PHPMD.CyclomaticComplexity)
     * @SuppressWarnings(PHPMD.NPathComplexity)
     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
     */
    public function validate(\Magento\Framework\Event\Observer $observer)
    {
        /* @var $quoteItem \Magento\Quote\Model\Quote\Item */
        $quoteItem = $observer->getEvent()->getItem();
        if (!$quoteItem ||
            !$quoteItem->getProductId() ||
            !$quoteItem->getQuote() ||
            $quoteItem->getQuote()->getIsSuperMode()
        ) {
            return;
        }
        $product = $quoteItem->getProduct();
        $qty = $quoteItem->getQty();

        /** @var \Magento\CatalogInventory\Model\Stock\Item $stockItem */
        $stockItem = $this->stockRegistry->getStockItem(
            $quoteItem->getProduct()->getId(),
            $quoteItem->getProduct()->getStore()->getWebsiteId()
        );

        if (!$stockItem instanceof \Magento\CatalogInventory\Api\Data\StockItemInterface) {
            throw new \Magento\Framework\Exception\LocalizedException(__('The stock item for Product is not valid.'));
        }

        /** @var \Magento\CatalogInventory\Api\Data\StockStatusInterface $stockStatus */
        $stockStatus = $this->stockRegistry->getStockStatus($product->getId(), $product->getStore()->getWebsiteId());

        /** @var \Magento\CatalogInventory\Api\Data\StockStatusInterface|bool $parentStockStatus */
        $parentStockStatus = false;

        /**
         * Check if product in stock. For composite products check base (parent) item stock status
         */
        if ($quoteItem->getParentItem()) {
            $product = $quoteItem->getParentItem()->getProduct();
            $parentStockStatus = $this->stockRegistry->getStockStatus(
                $product->getId(),
                $product->getStore()->getWebsiteId()
            );
        }

        if ($stockStatus) {
            /*if ($stockStatus->getStockStatus() == Stock::STOCK_OUT_OF_STOCK
                || $parentStockStatus && $parentStockStatus->getStockStatus() == Stock::STOCK_OUT_OF_STOCK
            )*/
            if (($stockStatus->getStockStatus() == Stock::STOCK_OUT_OF_STOCK
               || $parentStockStatus && $parentStockStatus->getStockStatus() == Stock::STOCK_OUT_OF_STOCK) && !$stockItem->getBackorders()
             )
             {
                $quoteItem->addErrorInfo(
                    'cataloginventory',
                    \Magento\CatalogInventory\Helper\Data::ERROR_QTY,
                    __('This product is out of stock.')
                );
                $quoteItem->getQuote()->addErrorInfo(
                    'stock',
                    'cataloginventory',
                    \Magento\CatalogInventory\Helper\Data::ERROR_QTY,
                    __('Some of the products are out of stock.')
                );
                return;
            } else {
                // Delete error from item and its quote, if it was set due to item out of stock
                $this->_removeErrorsFromQuoteAndItem($quoteItem, \Magento\CatalogInventory\Helper\Data::ERROR_QTY);
            }
        }

        /**
         * Check item for options
         */
        if (($options = $quoteItem->getQtyOptions()) && $qty > 0) {
            $qty = $product->getTypeInstance()->prepareQuoteItemQty($qty, $product);
            $quoteItem->setData('qty', $qty);
            if ($stockStatus) {
                $result = $this->stockState->checkQtyIncrements(
                    $product->getId(),
                    $qty,
                    $product->getStore()->getWebsiteId()
                );
                if ($result->getHasError()) {
                    $quoteItem->addErrorInfo(
                        'cataloginventory',
                        \Magento\CatalogInventory\Helper\Data::ERROR_QTY_INCREMENTS,
                        $result->getMessage()
                    );

                    $quoteItem->getQuote()->addErrorInfo(
                        $result->getQuoteMessageIndex(),
                        'cataloginventory',
                        \Magento\CatalogInventory\Helper\Data::ERROR_QTY_INCREMENTS,
                        $result->getQuoteMessage()
                    );
                } else {
                    // Delete error from item and its quote, if it was set due to qty problems
                    $this->_removeErrorsFromQuoteAndItem(
                        $quoteItem,
                        \Magento\CatalogInventory\Helper\Data::ERROR_QTY_INCREMENTS
                    );
                }
            }

            foreach ($options as $option) {
                $result = $this->optionInitializer->initialize($option, $quoteItem, $qty);
                if ($result->getHasError()) {
                    $option->setHasError(true);

                    $quoteItem->addErrorInfo(
                        'cataloginventory',
                        \Magento\CatalogInventory\Helper\Data::ERROR_QTY,
                        $result->getMessage()
                    );

                    $quoteItem->getQuote()->addErrorInfo(
                        $result->getQuoteMessageIndex(),
                        'cataloginventory',
                        \Magento\CatalogInventory\Helper\Data::ERROR_QTY,
                        $result->getQuoteMessage()
                    );
                } else {
                    // Delete error from item and its quote, if it was set due to qty lack
                    $this->_removeErrorsFromQuoteAndItem(
                        $quoteItem,
                        \Magento\CatalogInventory\Helper\Data::ERROR_QTY
                    );
                }
            }
        } else {
            $result = $this->stockItemInitializer->initialize($stockItem, $quoteItem, $qty);
            if ($result->getHasError()) {
                $quoteItem->addErrorInfo(
                    'cataloginventory',
                    \Magento\CatalogInventory\Helper\Data::ERROR_QTY,
                    $result->getMessage()
                );

                $quoteItem->getQuote()->addErrorInfo(
                    $result->getQuoteMessageIndex(),
                    'cataloginventory',
                    \Magento\CatalogInventory\Helper\Data::ERROR_QTY,
                    $result->getQuoteMessage()
                );
            } else {
                // Delete error from item and its quote, if it was set due to qty lack
                $this->_removeErrorsFromQuoteAndItem($quoteItem, \Magento\CatalogInventory\Helper\Data::ERROR_QTY);
            }
        }
    }

    /**
     * Removes error statuses from quote and item, set by this observer
     *
     * @param \Magento\Quote\Model\Quote\Item $item
     * @param int $code
     * @return void
     */
    protected function _removeErrorsFromQuoteAndItem($item, $code)
    {
        if ($item->getHasError()) {
            $params = ['origin' => 'cataloginventory', 'code' => $code];
            $item->removeErrorInfosByParams($params);
        }

        $quote = $item->getQuote();
        $quoteItems = $quote->getItemsCollection();
        $canRemoveErrorFromQuote = true;

        foreach ($quoteItems as $quoteItem) {
            if ($quoteItem->getItemId() == $item->getItemId()) {
                continue;
            }

            $errorInfos = $quoteItem->getErrorInfos();
            foreach ($errorInfos as $errorInfo) {
                if ($errorInfo['code'] == $code) {
                    $canRemoveErrorFromQuote = false;
                    break;
                }
            }

            if (!$canRemoveErrorFromQuote) {
                break;
            }
        }

        if ($quote->getHasError() && $canRemoveErrorFromQuote) {
            $params = ['origin' => 'cataloginventory', 'code' => $code];
            $quote->removeErrorInfosByParams(null, $params);
        }
    }
}
?>