Query for retrieving shopping cart information

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

@@ -40,8 +40,11 @@ public function execute(Quote $cart): array
             ];
         }
 
+        $appliedCoupon = $cart->getCouponCode();
+
         return [
             'items' => $items,
+            'applied_coupon' => $appliedCoupon ? ['code' => $appliedCoupon] : null
         ];
     }
 }

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

@@ -0,0 +1,67 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\QuoteGraphQl\Model\Resolver;
+
+use Magento\Framework\GraphQl\Config\Element\Field;
+use Magento\Framework\GraphQl\Exception\GraphQlInputException;
+use Magento\Framework\GraphQl\Query\ResolverInterface;
+use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
+use Magento\QuoteGraphQl\Model\Cart\GetCartForUser;
+use Magento\QuoteGraphQl\Model\Cart\ExtractDataFromCart;
+
+/**
+ * @inheritdoc
+ */
+class Cart implements ResolverInterface
+{
+    /**
+     * @var ExtractDataFromCart
+     */
+    private $extractDataFromCart;
+
+    /**
+     * @var GetCartForUser
+     */
+    private $getCartForUser;
+
+    /**
+     * @param GetCartForUser $getCartForUser
+     * @param ExtractDataFromCart $extractDataFromCart
+     */
+    public function __construct(
+        GetCartForUser $getCartForUser,
+        ExtractDataFromCart $extractDataFromCart
+    ) {
+        $this->getCartForUser = $getCartForUser;
+        $this->extractDataFromCart = $extractDataFromCart;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function resolve(Field $field, $context, ResolveInfo $info, array $value = null, array $args = null)
+    {
+        if (!isset($args['cart_id'])) {
+            throw new GraphQlInputException(__('Required parameter "cart_id" is missing'));
+        }
+        $maskedCartId = $args['cart_id'];
+
+        $currentUserId = $context->getUserId();
+        $cart = $this->getCartForUser->execute($maskedCartId, $currentUserId);
+
+        $data = array_merge(
+            [
+                'cart_id' => $maskedCartId,
+                'model' => $cart
+            ],
+            $this->extractDataFromCart->execute($cart)
+        );
+
+        return $data;
+    }
+}

app/code/Magento/QuoteGraphQl/etc/schema.graphqls

@@ -2,7 +2,7 @@
 # See COPYING.txt for license details.
 
 type Query {
-    getAvailableShippingMethodsOnCart(input: AvailableShippingMethodsOnCartInput): AvailableShippingMethodsOnCartOutput @doc(description:"Returns available shipping methods for cart by address/address_id")
+    Cart(cart_id: String!): Cart @resolver (class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\Cart") @doc(description:"Returns information about shopping cart")
 }
 
 type Mutation {
@@ -84,10 +84,6 @@ input AvailableShippingMethodsOnCartInput {
     address: CartAddressInput
 }
 
-type AvailableShippingMethodsOnCartOutput {
-    available_shipping_methods: [CheckoutShippingMethod]
-}
-
 input ApplyCouponToCartInput {
     cart_id: String!
     coupon_code: String!

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

@@ -0,0 +1,171 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\GraphQl\Quote;
+
+use Magento\Integration\Api\CustomerTokenServiceInterface;
+use Magento\Quote\Model\Quote;
+use Magento\Quote\Model\QuoteIdToMaskedQuoteIdInterface;
+use Magento\Quote\Model\ResourceModel\Quote as QuoteResource;
+use Magento\TestFramework\Helper\Bootstrap;
+use Magento\TestFramework\TestCase\GraphQlAbstract;
+
+/**
+ * Test for getting cart information
+ */
+class GetCartTest extends GraphQlAbstract
+{
+    /**
+     * @var CustomerTokenServiceInterface
+     */
+    private $customerTokenService;
+
+    /**
+     * @var QuoteResource
+     */
+    private $quoteResource;
+
+    /**
+     * @var Quote
+     */
+    private $quote;
+
+    /**
+     * @var QuoteIdToMaskedQuoteIdInterface
+     */
+    private $quoteIdToMaskedId;
+
+    /**
+     * @inheritdoc
+     */
+    protected function setUp()
+    {
+        $objectManager = Bootstrap::getObjectManager();
+        $this->quoteResource = $objectManager->create(QuoteResource::class);
+        $this->quote = $objectManager->create(Quote::class);
+        $this->quoteIdToMaskedId = $objectManager->create(QuoteIdToMaskedQuoteIdInterface::class);
+        $this->customerTokenService = $objectManager->get(CustomerTokenServiceInterface::class);
+    }
+
+    /**
+     * @magentoApiDataFixture Magento/Checkout/_files/quote_with_items_saved.php
+     */
+    public function testGetOwnCartForRegisteredCustomer()
+    {
+        $reservedOrderId = 'test_order_item_with_items';
+        $this->quoteResource->load(
+            $this->quote,
+            $reservedOrderId,
+            'reserved_order_id'
+        );
+
+        $maskedQuoteId = $this->quoteIdToMaskedId->execute((int)$this->quote->getId());
+        $query = $this->prepareGetCartQuery($maskedQuoteId);
+
+        $response = $this->sendRequestWithToken($query);
+
+        self::assertArrayHasKey('Cart', $response);
+        self::assertNotEmpty($response['Cart']['items']);
+        self::assertNotEmpty($response['Cart']['addresses']);
+    }
+
+    /**
+     * @magentoApiDataFixture Magento/Checkout/_files/quote_with_items_saved.php
+     */
+    public function testGetCartFromAnotherCustomer()
+    {
+        $reservedOrderId = 'test_order_item_with_items';
+        $this->quoteResource->load(
+            $this->quote,
+            $reservedOrderId,
+            'reserved_order_id'
+        );
+
+
+        $maskedQuoteId = $this->quoteIdToMaskedId->execute((int)$this->quote->getId());
+        $query = $this->prepareGetCartQuery($maskedQuoteId);
+
+        self::expectExceptionMessage("The current user cannot perform operations on cart \"$maskedQuoteId\"");
+
+        $this->graphQlQuery($query);
+    }
+
+    /**
+     * @magentoApiDataFixture Magento/Checkout/_files/active_quote.php
+     */
+    public function testGetCartForGuest()
+    {
+        $reservedOrderId = 'test_order_1';
+        $this->quoteResource->load(
+            $this->quote,
+            $reservedOrderId,
+            'reserved_order_id'
+        );
+
+        $maskedQuoteId = $this->quoteIdToMaskedId->execute((int)$this->quote->getId());
+        $query = $this->prepareGetCartQuery($maskedQuoteId);
+
+        $response = $this->graphQlQuery($query);
+
+        self::assertArrayHasKey('Cart', $response);
+    }
+
+    public function testGetNonExistentCart()
+    {
+        $maskedQuoteId = 'non_existent_masked_id';
+        $query = $this->prepareGetCartQuery($maskedQuoteId);
+
+        self::expectExceptionMessage("Could not find a cart with ID \"$maskedQuoteId\"");
+
+        $this->graphQlQuery($query);
+    }
+
+    /**
+     * Generates query for setting the specified shipping method on cart
+     *
+     * @param string $maskedQuoteId
+     * @return string
+     */
+    private function prepareGetCartQuery(
+        string $maskedQuoteId
+    ) : string {
+        return <<<QUERY
+{
+  Cart(cart_id: "$maskedQuoteId") {
+    applied_coupon {
+    	  code
+    }
+    items {
+      id
+    }
+    addresses {
+      firstname,
+      lastname,
+      address_type
+    }
+  }
+}
+
+QUERY;
+    }
+
+    /**
+     * Sends a GraphQL request with using a bearer token
+     *
+     * @param string $query
+     * @return array
+     * @throws \Magento\Framework\Exception\AuthenticationException
+     */
+    private function sendRequestWithToken(string $query): array
+    {
+
+        $customerToken = $this->customerTokenService->createCustomerAccessToken('[email protected]', 'password');
+        $headerMap = ['Authorization' => 'Bearer ' . $customerToken];
+
+        return $this->graphQlQuery($query, [], '', $headerMap);
+    }
+}

dev/tests/integration/testsuite/Magento/Checkout/_files/active_quote.php

@@ -9,3 +9,11 @@
     ->setIsMultiShipping(false)
     ->setReservedOrderId('test_order_1')
     ->save();
+
+/** @var \Magento\Quote\Model\QuoteIdMask $quoteIdMask */
+$quoteIdMask = \Magento\TestFramework\Helper\Bootstrap::getObjectManager()
+    ->create(\Magento\Quote\Model\QuoteIdMaskFactory::class)
+    ->create();
+$quoteIdMask->setQuoteId($quote->getId());
+$quoteIdMask->setDataChanges(true);
+$quoteIdMask->save();