MC-39104: 2 error messages in Cart when product is out of stock

Author: rostyslav-hymon

app/code/Magento/CatalogInventory/Model/Quote/Item/QuantityValidator.php

@@ -157,7 +157,9 @@ public function validate(Observer $observer)
             if ($stockStatus->getStockStatus() === Stock::STOCK_OUT_OF_STOCK
                     || $parentStockStatus && $parentStockStatus->getStockStatus() == Stock::STOCK_OUT_OF_STOCK
             ) {
-                if (!$quoteItem->getStockStateResult() && !$quoteItem->getStockStateResult()->getHasError()) {
+                $hasError = $quoteItem->getStockStateResult()
+                    ? $quoteItem->getStockStateResult()->getHasError() : false;
+                if (!$hasError) {
                     $quoteItem->addErrorInfo(
                         'cataloginventory',
                         Data::ERROR_QTY,

app/code/Magento/CatalogInventory/Test/Unit/Model/Quote/Item/QuantityValidator/Initializer/QuantityValidatorTest.php

@@ -153,7 +153,7 @@ protected function setUp(): void
             ->getMock();
         $this->storeMock = $this->createMock(Store::class);
         $this->quoteItemMock = $this->getMockBuilder(Item::class)
-            ->addMethods(['getProductId', 'getHasError'])
+            ->addMethods(['getProductId', 'getHasError', 'getStockStateResult'])
             ->onlyMethods(
                 [
                     'getQuote',
@@ -460,6 +460,54 @@ public function testException()
         $this->quantityValidator->validate($this->observerMock);
     }
 
+    /**
+     * This tests the scenario when the error is in the quote item already
+     *
+     * @return void
+     */
+    public function testValidateOutStockWithAlreadyErrorInQuoteItem(): void
+    {
+        $this->createInitialStub(1);
+        $resultMock = $this->getMockBuilder(DataObject::class)
+            ->addMethods(['checkQtyIncrements', 'getMessage', 'getQuoteMessage', 'getHasError'])
+            ->getMock();
+        $resultMock->method('getHasError')
+            ->willReturn(true);
+        $this->stockRegistryMock->method('getStockItem')
+            ->willReturn($this->stockItemMock);
+        $this->stockRegistryMock->expects($this->at(1))
+            ->method('getStockStatus')
+            ->willReturn($this->stockStatusMock);
+        $this->quoteItemMock->method('getParentItem')
+            ->willReturn($this->parentItemMock);
+        $this->quoteItemMock->method('getStockStateResult')
+            ->willReturn($resultMock);
+        $this->stockRegistryMock->expects($this->at(2))
+            ->method('getStockStatus')
+            ->willReturn($this->parentStockItemMock);
+        $this->parentStockItemMock->method('getStockStatus')
+            ->willReturn(0);
+        $this->stockStatusMock->expects($this->atLeastOnce())
+            ->method('getStockStatus')
+            ->willReturn(1);
+        $this->quoteItemMock->expects($this->never())
+            ->method('addErrorInfo')
+            ->with(
+                'cataloginventory',
+                Data::ERROR_QTY,
+                __('This product is out of stock.')
+            );
+        $this->quoteMock->expects($this->once())
+            ->method('addErrorInfo')
+            ->with(
+                'stock',
+                'cataloginventory',
+                Data::ERROR_QTY,
+                __('Some of the products are out of stock.')
+            );
+        $this->quantityValidator->validate($this->observerMock);
+    }
+
     /**
      * @param $qty
      * @param $hasError