Merge forwardport of #11997 to 2.3-develop branch

Applied pull request patch https://github.com/magento/magento2/pull/11997.patch (created by @nmalevanec) based on commit(s):
  1. 0db2b08

Fixed GitHub Issues in 2.3-develop branch:
  - #11941: Invoice for products that use qty decimal rounds down to whole number (reported by @ralbin)

app/code/Magento/CatalogInventory/Observer/AddStockItemsObserver.php

@@ -0,0 +1,77 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\CatalogInventory\Observer;
+
+use Magento\Catalog\Model\Product;
+use Magento\Catalog\Model\ResourceModel\Product\Collection;
+use Magento\CatalogInventory\Api\StockConfigurationInterface;
+use Magento\CatalogInventory\Api\StockItemCriteriaInterfaceFactory;
+use Magento\CatalogInventory\Api\StockItemRepositoryInterface;
+use Magento\Framework\Event\Observer;
+use Magento\Framework\Event\ObserverInterface;
+
+/**
+ * Add Stock items to product collection.
+ */
+class AddStockItemsObserver implements ObserverInterface
+{
+    /**
+     * @var StockItemCriteriaInterfaceFactory
+     */
+    private $criteriaInterfaceFactory;
+
+    /**
+     * @var StockItemRepositoryInterface
+     */
+    private $stockItemRepository;
+
+    /**
+     * @var StockConfigurationInterface
+     */
+    private $stockConfiguration;
+
+    /**
+     * AddStockItemsObserver constructor.
+     *
+     * @param StockItemCriteriaInterfaceFactory $criteriaInterfaceFactory
+     * @param StockItemRepositoryInterface $stockItemRepository
+     * @param StockConfigurationInterface $stockConfiguration
+     */
+    public function __construct(
+        StockItemCriteriaInterfaceFactory $criteriaInterfaceFactory,
+        StockItemRepositoryInterface $stockItemRepository,
+        StockConfigurationInterface $stockConfiguration
+    ) {
+        $this->criteriaInterfaceFactory = $criteriaInterfaceFactory;
+        $this->stockItemRepository = $stockItemRepository;
+        $this->stockConfiguration = $stockConfiguration;
+    }
+
+    /**
+     * Add stock items to products in collection.
+     *
+     * @param Observer $observer
+     * @return void
+     */
+    public function execute(Observer $observer)
+    {
+        /** @var Collection $productCollection */
+        $productCollection = $observer->getData('collection');
+        $productIds = array_keys($productCollection->getItems());
+        $criteria = $this->criteriaInterfaceFactory->create();
+        $criteria->setProductsFilter($productIds);
+        $criteria->setScopeFilter($this->stockConfiguration->getDefaultScopeId());
+        $stockItemCollection = $this->stockItemRepository->getList($criteria);
+        foreach ($stockItemCollection->getItems() as $item) {
+            /** @var Product $product */
+            $product = $productCollection->getItemById($item->getProductId());
+            $productExtension = $product->getExtensionAttributes();
+            $productExtension->setStockItem($item);
+            $product->setExtensionAttributes($productExtension);
+        }
+    }
+}

app/code/Magento/CatalogInventory/Test/Unit/Observer/AddStockItemsObserverTest.php

@@ -0,0 +1,165 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\CatalogInventory\Test\Unit\Observer;
+
+use Magento\Catalog\Api\Data\ProductExtensionInterface;
+use Magento\Catalog\Model\Product;
+use Magento\Catalog\Model\ResourceModel\Product\Collection as ProductCollection;
+use Magento\CatalogInventory\Api\Data\StockItemCollectionInterface;
+use Magento\CatalogInventory\Api\Data\StockItemInterface;
+use Magento\CatalogInventory\Api\StockConfigurationInterface;
+use Magento\CatalogInventory\Api\StockItemCriteriaInterface;
+use Magento\CatalogInventory\Api\StockItemCriteriaInterfaceFactory;
+use Magento\CatalogInventory\Api\StockItemRepositoryInterface;
+use Magento\CatalogInventory\Observer\AddStockItemsObserver;
+use Magento\Framework\Event\Observer;
+use Magento\Framework\TestFramework\Unit\Helper\ObjectManager;
+use PHPUnit\Framework\TestCase;
+
+class AddStockItemsObserverTest extends TestCase
+{
+    /**
+     * Test subject.
+     *
+     * @var AddStockItemsObserver
+     */
+    private $subject;
+    /**
+     * @var StockItemCriteriaInterfaceFactory|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $criteriaInterfaceFactoryMock;
+
+    /**
+     * @var StockItemRepositoryInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $stockItemRepositoryMock;
+
+    /**
+     * @var StockConfigurationInterface|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $stockConfigurationMock;
+
+    /**
+     * @inheritdoc
+     */
+    protected function setUp()
+    {
+        $objectManager = new ObjectManager($this);
+        $this->criteriaInterfaceFactoryMock = $this->getMockBuilder(StockItemCriteriaInterfaceFactory::class)
+            ->setMethods(['create'])
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+        $this->stockItemRepositoryMock = $this->getMockBuilder(StockItemRepositoryInterface::class)
+            ->setMethods(['getList'])
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+        $this->stockConfigurationMock = $this->getMockBuilder(StockConfigurationInterface::class)
+            ->setMethods(['getDefaultScopeId'])
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+        $this->subject = $objectManager->getObject(
+            AddStockItemsObserver::class,
+            [
+                'criteriaInterfaceFactory' => $this->criteriaInterfaceFactoryMock,
+                'stockItemRepository' => $this->stockItemRepositoryMock,
+                'stockConfiguration' => $this->stockConfigurationMock
+            ]
+        );
+    }
+
+    /**
+     * Test AddStockItemsObserver::execute() add stock item to product as extension attribute.
+     */
+    public function testExecute()
+    {
+        $productId = 1;
+        $defaultScopeId = 0;
+
+        $criteria = $this->getMockBuilder(StockItemCriteriaInterface::class)
+            ->setMethods(['setProductsFilter', 'setScopeFilter'])
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+        $criteria->expects(self::once())
+            ->method('setProductsFilter')
+            ->with(self::identicalTo([$productId]))
+            ->willReturn(true);
+        $criteria->expects(self::once())
+            ->method('setScopeFilter')
+            ->with(self::identicalTo($defaultScopeId))
+            ->willReturn(true);
+
+        $this->criteriaInterfaceFactoryMock->expects(self::once())
+            ->method('create')
+            ->willReturn($criteria);
+        $stockItemCollection = $this->getMockBuilder(StockItemCollectionInterface::class)
+            ->setMethods(['getItems'])
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+        $stockItem = $this->getMockBuilder(StockItemInterface::class)
+            ->setMethods(['getProductId'])
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+        $stockItem->expects(self::once())
+            ->method('getProductId')
+            ->willReturn($productId);
+
+        $stockItemCollection->expects(self::once())
+            ->method('getItems')
+            ->willReturn([$stockItem]);
+
+        $this->stockItemRepositoryMock->expects(self::once())
+            ->method('getList')
+            ->with(self::identicalTo($criteria))
+            ->willReturn($stockItemCollection);
+
+        $this->stockConfigurationMock->expects(self::once())
+            ->method('getDefaultScopeId')
+            ->willReturn($defaultScopeId);
+
+        $productExtension = $this->getMockBuilder(ProductExtensionInterface::class)
+            ->setMethods(['setStockItem'])
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+        $productExtension->expects(self::once())
+            ->method('setStockItem')
+            ->with(self::identicalTo($stockItem));
+
+        $product = $this->getMockBuilder(Product::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        $product->expects(self::once())
+            ->method('getExtensionAttributes')
+            ->willReturn($productExtension);
+        $product->expects(self::once())
+            ->method('setExtensionAttributes')
+            ->with(self::identicalTo($productExtension))
+            ->willReturnSelf();
+
+        /** @var ProductCollection|\PHPUnit_Framework_MockObject_MockObject $productCollection */
+        $productCollection = $this->getMockBuilder(ProductCollection::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        $productCollection->expects(self::once())
+            ->method('getItems')
+            ->willReturn([$productId => $product]);
+        $productCollection->expects(self::once())
+            ->method('getItemById')
+            ->with(self::identicalTo($productId))
+            ->willReturn($product);
+
+        /** @var Observer|\PHPUnit_Framework_MockObject_MockObject $observer */
+        $observer = $this->getMockBuilder(Observer::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        $observer->expects(self::once())
+            ->method('getData')
+            ->with('collection')
+            ->willReturn($productCollection);
+
+        $this->subject->execute($observer);
+    }
+}

app/code/Magento/CatalogInventory/etc/events.xml

@@ -39,4 +39,7 @@
     <event name="admin_system_config_changed_section_cataloginventory">
         <observer name="inventory" instance="Magento\CatalogInventory\Observer\UpdateItemsStockUponConfigChangeObserver"/>
     </event>
+    <event name="sales_quote_item_collection_products_after_load">
+        <observer name="add_stock_items" instance="Magento\CatalogInventory\Observer\AddStockItemsObserver"/>
+    </event>
 </config>