ACP2E-4283: updateCartItems GraphQL incorrect error response

- Updated solution with test

Author: arnobsh

app/code/Magento/QuoteGraphQl/Observer/CheckAndUpdateQtyObserver.php

@@ -0,0 +1,30 @@
+<?php
+/**
+ * Copyright 2025 Adobe
+ * All Rights Reserved.
+ */
+declare(strict_types=1);
+
+namespace Magento\QuoteGraphQl\Observer;
+
+use Magento\Framework\Event\Observer;
+use Magento\Framework\Event\ObserverInterface;
+
+class CheckAndUpdateQtyObserver implements ObserverInterface
+{
+    /**
+     * Check and update the item qty in case of error
+     *
+     * @param Observer $observer
+     * @return void
+     */
+    public function execute(Observer $observer):void
+    {
+        $item = $observer->getEvent()->getItem();
+
+        if ($item && $item->getHasError()) {
+            $item->setUseOldQty(true);
+            $item->getQuote()->setHasError(true);
+        }
+    }
+}

app/code/Magento/QuoteGraphQl/etc/graphql/events.xml

@@ -10,4 +10,7 @@
         <observer name="sendEmail" instance="Magento\Quote\Observer\SubmitObserver"/>
         <observer name="sendInvoiceEmail" instance="Magento\Quote\Observer\SendInvoiceEmailObserver"/>
     </event>
+    <event name="sales_quote_item_qty_set_after">
+        <observer name="checkAndUpdateQty" instance="Magento\QuoteGraphQl\Observer\CheckAndUpdateQtyObserver"/>
+    </event>
 </config>

dev/tests/api-functional/testsuite/Magento/GraphQl/Quote/Customer/UpdateCartItemsTest.php

@@ -1,17 +1,27 @@
 <?php
 /**
- * Copyright © Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
+ * Copyright 2019 Adobe
+ * All Rights Reserved.
  */
 declare(strict_types=1);
 
 namespace Magento\GraphQl\Quote\Customer;
 
 use Magento\Catalog\Api\ProductRepositoryInterface;
+use Magento\Catalog\Test\Fixture\Product as ProductFixture;
+use Magento\Checkout\Test\Fixture\SetShippingAddress as SetShippingAddressFixture;
+use Magento\Customer\Test\Fixture\Customer as CustomerFixture;
+use Magento\Framework\Exception\NoSuchEntityException;
 use Magento\Integration\Api\CustomerTokenServiceInterface;
 use Magento\Quote\Model\QuoteFactory;
 use Magento\Quote\Model\QuoteIdToMaskedQuoteIdInterface;
 use Magento\Quote\Model\ResourceModel\Quote as QuoteResource;
+use Magento\Quote\Test\Fixture\AddProductToCart as AddProductToCartFixture;
+use Magento\Quote\Test\Fixture\CustomerCart as CustomerCartFixture;
+use Magento\Quote\Test\Fixture\QuoteIdMask;
+use Magento\TestFramework\Fixture\DataFixture;
+use Magento\TestFramework\Fixture\DataFixtureStorage;
+use Magento\TestFramework\Fixture\DataFixtureStorageManager;
 use Magento\TestFramework\Helper\Bootstrap;
 use Magento\TestFramework\TestCase\GraphQlAbstract;
 
@@ -45,6 +55,11 @@ class UpdateCartItemsTest extends GraphQlAbstract
      */
     private $productRepository;
 
+    /**
+     * @var DataFixtureStorage
+     */
+    private $fixtures;
+
     protected function setUp(): void
     {
         $objectManager = Bootstrap::getObjectManager();
@@ -53,6 +68,7 @@ protected function setUp(): void
         $this->quoteIdToMaskedId = $objectManager->get(QuoteIdToMaskedQuoteIdInterface::class);
         $this->customerTokenService = $objectManager->get(CustomerTokenServiceInterface::class);
         $this->productRepository = $objectManager->get(ProductRepositoryInterface::class);
+        $this->fixtures = DataFixtureStorageManager::getStorage();
     }
 
     /**
@@ -136,6 +152,126 @@ public function testUpdateNonExistentItem()
         $this->assertEquals('COULD_NOT_FIND_CART_ITEM', $responseError['code']);
     }
 
+    /**
+     *  Test and check update with not enough quantity exception
+     */
+    #[
+        DataFixture(ProductFixture::class, as: 'product'),
+        DataFixture(CustomerFixture::class, ['email' => 'customer@example.com'], as: 'customer'),
+        DataFixture(CustomerCartFixture::class, ['customer_id' => '$customer.id$'], as: 'cart'),
+        DataFixture(
+            AddProductToCartFixture::class,
+            ['cart_id' => '$cart.id$', 'product_id' => '$product.id$', 'qty' => 100]
+        ),
+        DataFixture(SetShippingAddressFixture::class, ['cart_id' => '$cart.id$']),
+        DataFixture(QuoteIdMask::class, ['cart_id' => '$cart.id$'], 'quoteIdMask'),
+    ]
+    public function testUpdateWithNotEnoughQuantityException()
+    {
+        $productSku = $this->fixtures->get('product')->getSku();
+        $maskedQuoteId = $this->fixtures->get('quoteIdMask')->getMaskedId();
+        $query = $this->getCartQuery($maskedQuoteId);
+        $cartResponse = $this->graphQlQuery($query, [], '', $this->getHeaderMap());
+
+        $this->assertArrayHasKey('cart', $cartResponse);
+        $this->assertArrayHasKey('itemsV2', $cartResponse['cart']);
+        $items = $cartResponse['cart']['itemsV2']['items'];
+        $itemId = $items[0]['uid'];
+        $this->assertNotEmpty($itemId);
+
+        $updateCartItemsMutation = $this->updateCartItemsMutation(
+            $maskedQuoteId,
+            $itemId,
+            1000
+        );
+        $updatedCartResponse = $this->graphQlMutation($updateCartItemsMutation, [], '', $this->getHeaderMap());
+        $this->assertArrayHasKey('errors', $updatedCartResponse['updateCartItems']);
+
+        $responseError = $updatedCartResponse['updateCartItems']['errors'][0];
+
+        $this->assertEquals('INSUFFICIENT_STOCK', $responseError['code']);
+        $this->assertEquals(
+            "Could not update the product with SKU {$productSku}: Not enough items for sale",
+            $responseError['message']
+        );
+    }
+
+        /**
+         * Generates GraphQl query for retrieving cart items prices [original_item_price & original_row_total]
+         *
+         * @param string $customer_cart_id
+         * @return string
+         */
+    private function getCartQuery(string $customer_cart_id): string
+    {
+        return <<<QUERY
+        {
+          cart(cart_id: "$customer_cart_id") {
+            itemsV2 {
+              total_count
+              items {
+                uid
+                product {
+                  name
+                  sku
+                }
+                quantity
+              }
+            }
+          }
+        }
+        QUERY;
+    }
+
+    /**
+     * Generate GraphQL mutation for updating product to cart
+     *
+     * @param string $cartId
+     * @param string $cartItemId
+     * @param int $qty
+     * @return string
+     */
+    private function updateCartItemsMutation(string $cartId, string $cartItemId, int $qty = 1): string
+    {
+        return <<<MUTATION
+        mutation{
+        updateCartItems(
+            input: {
+              cart_id: "{$cartId}",
+              cart_items: [
+                {
+                  cart_item_uid: "{$cartItemId}"
+                  quantity: {$qty}
+                }
+              ]
+            }
+          ) {
+              cart {
+                  itemsV2 {
+                    items {
+                      product {
+                        name
+                      }
+                      quantity
+                    }
+                  }
+                  prices {
+                    grand_total{
+                      value
+                      currency
+                    }
+                  }
+              }
+              errors {
+                  code
+                  message
+              }
+
+            }
+        }
+        MUTATION;
+    }
+
     /**
      * @magentoApiDataFixture Magento/Checkout/_files/quote_with_address_saved.php
      * @magentoApiDataFixture Magento/Checkout/_files/quote_with_virtual_product_saved.php
@@ -232,6 +368,7 @@ public function testUpdateItemInAnotherCustomerCart()
      * @param string $errorCode
      * @dataProvider dataProviderUpdateWithMissedRequiredParameters
      * @magentoApiDataFixture Magento/Checkout/_files/quote_with_address_saved.php
+     * @throws NoSuchEntityException
      */
     public function testUpdateWithMissedItemRequiredParameters(string $input, string $message, string $errorCode)
     {