MAGETWO-96441: "Custom price" can't be removed during order creation in admin

Author: ameysar

app/code/Magento/Quote/Model/Quote/Item/Updater.php

@@ -60,6 +60,7 @@ public function __construct(
 
     /**
      * Update quote item qty.
+     *
      * Custom price is updated in case 'custom_price' value exists
      *
      * @param Item $item
@@ -145,8 +146,8 @@ protected function unsetCustomPrice(Item $item)
             $item->addOption($infoBuyRequest);
         }
 
-        $item->unsetData('custom_price');
-        $item->unsetData('original_custom_price');
+        $item->setData('custom_price', null);
+        $item->setData('original_custom_price', null);
     }
 
     /**

app/code/Magento/Quote/Test/Unit/Model/Quote/Item/UpdaterTest.php

@@ -67,7 +67,7 @@ protected function setUp()
                 'addOption',
                 'setCustomPrice',
                 'setOriginalCustomPrice',
-                'unsetData',
+                'setData',
                 'hasData',
                 'setIsQtyDecimal'
             ]);
@@ -301,7 +301,7 @@ public function testUpdateUnsetCustomPrice()
                 'setProduct',
                 'getData',
                 'unsetData',
-                'hasData'
+                'hasData',
             ]);
         $buyRequestMock->expects($this->never())->method('setCustomPrice');
         $buyRequestMock->expects($this->once())->method('getData')->will($this->returnValue([]));
@@ -353,7 +353,11 @@ public function testUpdateUnsetCustomPrice()
             ->will($this->returnValue($buyRequestMock));
 
         $this->itemMock->expects($this->exactly(2))
-            ->method('unsetData');
+            ->method('setData')
+            ->withConsecutive(
+                ['custom_price', null],
+                ['original_custom_price', null]
+            );
 
         $this->itemMock->expects($this->once())
             ->method('hasData')

dev/tests/integration/testsuite/Magento/Quote/Model/Quote/Item/UpdaterTest.php

@@ -0,0 +1,63 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Quote\Model\Quote\Item;
+
+use Magento\Quote\Api\CartItemRepositoryInterface;
+use Magento\Quote\Api\Data\CartItemInterface;
+use Magento\Quote\Model\Quote;
+use Magento\TestFramework\Helper\Bootstrap;
+
+/**
+ * Tests \Magento\Quote\Model\Quote\Item\Updater
+ */
+class UpdaterTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @var Updater
+     */
+    private $updater;
+
+    /**
+     * @var \Magento\Framework\ObjectManagerInterface
+     */
+    private $objectManager;
+
+    /**
+     * @inheritdoc
+     */
+    protected function setUp()
+    {
+        $this->objectManager = Bootstrap::getObjectManager();
+        $this->updater = $this->objectManager->create(Updater::class);
+    }
+
+    /**
+     * @magentoDataFixture Magento/Sales/_files/quote_with_custom_price.php
+     * @return void
+     */
+    public function testUpdate(): void
+    {
+        /** @var CartItemRepositoryInterface $quoteItemRepository */
+        $quoteItemRepository = $this->objectManager->create(CartItemRepositoryInterface::class);
+        /** @var Quote $quote */
+        $quote = $this->objectManager->create(Quote::class);
+        $quoteId = $quote->load('test01', 'reserved_order_id')->getId();
+        /** @var CartItemInterface[] $quoteItems */
+        $quoteItems = $quoteItemRepository->getList($quoteId);
+        /** @var CartItemInterface $actualQuoteItem */
+        $actualQuoteItem = array_pop($quoteItems);
+        $this->assertInstanceOf(CartItemInterface::class, $actualQuoteItem);
+
+        $this->updater->update($actualQuoteItem, ['qty' => 1]);
+
+        $this->assertNull(
+            $actualQuoteItem->getCustomPrice(),
+            'Item custom price has to be null'
+        );
+    }
+}

dev/tests/integration/testsuite/Magento/Sales/_files/quote_with_custom_price.php

@@ -0,0 +1,22 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+include __DIR__ . '/quote.php';
+
+$buyRequest = \Magento\TestFramework\Helper\Bootstrap::getObjectManager()->create(
+    \Magento\Framework\DataObject::class,
+    [
+        'data' => [
+            'qty' => 1,
+            'custom_price' => 12,
+        ],
+    ]
+);
+/** @var \Magento\Quote\Model\Quote $items */
+$items = $quote->getItemsCollection()->getItems();
+$quoteItem = reset($items);
+$quote->updateItem($quoteItem->getId(), $buyRequest)->save();

dev/tests/integration/testsuite/Magento/Sales/_files/quote_with_custom_price_rollback.php

@@ -0,0 +1,8 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+include __DIR__ . '/quote_rollback.php';