[Checkout] Prevent generating new masked quote id for same quote

app/code/Magento/QuoteGraphQl/Model/Cart/CreateEmptyCartForCustomer.php

@@ -8,7 +8,9 @@
 namespace Magento\QuoteGraphQl\Model\Cart;
 
 use Magento\Quote\Api\CartManagementInterface;
+use Magento\Quote\Model\QuoteIdMask;
 use Magento\Quote\Model\QuoteIdMaskFactory;
+use Magento\Quote\Model\QuoteIdToMaskedQuoteIdInterface;
 use Magento\Quote\Model\ResourceModel\Quote\QuoteIdMask as QuoteIdMaskResourceModel;
 
 /**
@@ -31,19 +33,27 @@ class CreateEmptyCartForCustomer
      */
     private $quoteIdMaskResourceModel;
 
+    /**
+     * @var QuoteIdToMaskedQuoteIdInterface
+     */
+    private $quoteIdToMaskedQuoteId;
+
     /**
      * @param CartManagementInterface $cartManagement
      * @param QuoteIdMaskFactory $quoteIdMaskFactory
      * @param QuoteIdMaskResourceModel $quoteIdMaskResourceModel
+     * @param QuoteIdToMaskedQuoteIdInterface $quoteIdToMaskedQuoteId
      */
     public function __construct(
         CartManagementInterface $cartManagement,
         QuoteIdMaskFactory $quoteIdMaskFactory,
-        QuoteIdMaskResourceModel $quoteIdMaskResourceModel
+        QuoteIdMaskResourceModel $quoteIdMaskResourceModel,
+        QuoteIdToMaskedQuoteIdInterface $quoteIdToMaskedQuoteId
     ) {
         $this->cartManagement = $cartManagement;
         $this->quoteIdMaskFactory = $quoteIdMaskFactory;
         $this->quoteIdMaskResourceModel = $quoteIdMaskResourceModel;
+        $this->quoteIdToMaskedQuoteId = $quoteIdToMaskedQuoteId;
     }
 
     /**
@@ -55,16 +65,56 @@ public function __construct(
      */
     public function execute(int $customerId, string $predefinedMaskedQuoteId = null): string
     {
-        $quoteId = $this->cartManagement->createEmptyCartForCustomer($customerId);
+        $quoteId = (int) $this->cartManagement->createEmptyCartForCustomer($customerId);
+
+        if ($predefinedMaskedQuoteId !== null) {
+            $maskedId = $this->createPredefinedMaskId($quoteId, $predefinedMaskedQuoteId);
+        } else {
+            $maskedId = $this->getQuoteMaskId($quoteId);
+        }
+
+        return $maskedId;
+    }
 
+    /**
+     * Create quote masked id from predefined value
+     *
+     * @param int $quoteId
+     * @param string $maskId
+     * @return string
+     * @throws \Magento\Framework\Exception\AlreadyExistsException
+     */
+    private function createPredefinedMaskId(int $quoteId, string $maskId): string
+    {
+        /** @var QuoteIdMask $quoteIdMask */
         $quoteIdMask = $this->quoteIdMaskFactory->create();
         $quoteIdMask->setQuoteId($quoteId);
-
-        if (isset($predefinedMaskedQuoteId)) {
-            $quoteIdMask->setMaskedId($predefinedMaskedQuoteId);
-        }
+        $quoteIdMask->setMaskedId($maskId);
 
         $this->quoteIdMaskResourceModel->save($quoteIdMask);
+
         return $quoteIdMask->getMaskedId();
     }
+
+    /**
+     * Fetch or create masked id for customer's active quote
+     *
+     * @param int $quoteId
+     * @return string
+     * @throws \Magento\Framework\Exception\AlreadyExistsException
+     * @throws \Magento\Framework\Exception\NoSuchEntityException
+     */
+    private function getQuoteMaskId(int $quoteId): string
+    {
+        $maskedId = $this->quoteIdToMaskedQuoteId->execute($quoteId);
+        if ($maskedId === '') {
+            $quoteIdMask = $this->quoteIdMaskFactory->create();
+            $quoteIdMask->setQuoteId($quoteId);
+
+            $this->quoteIdMaskResourceModel->save($quoteIdMask);
+            $maskedId = $quoteIdMask->getMaskedId();
+        }
+
+        return $maskedId;
+    }
 }

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

@@ -73,6 +73,25 @@ public function testCreateEmptyCart()
         self::assertEquals('default', $guestCart->getStore()->getCode());
     }
 
+    /**
+     * @magentoApiDataFixture Magento/Customer/_files/customer.php
+     */
+    public function testCreateEmptyMultipleRequestsCart()
+    {
+        $query = $this->getQuery();
+        $response = $this->graphQlMutation($query, [], '', $this->getHeaderMapWithCustomerToken());
+
+        self::assertArrayHasKey('createEmptyCart', $response);
+        self::assertNotEmpty($response['createEmptyCart']);
+        $maskedCartId = $response['createEmptyCart'];
+
+        $response = $this->graphQlMutation($query, [], '', $this->getHeaderMapWithCustomerToken());
+        self::assertArrayHasKey('createEmptyCart', $response);
+        self::assertNotEmpty($response['createEmptyCart']);
+
+        self::assertEquals($maskedCartId, $response['createEmptyCart']);
+    }
+
     /**
      * @magentoApiDataFixture Magento/Store/_files/second_store.php
      * @magentoApiDataFixture Magento/Customer/_files/customer.php