Prototype: setPaymentMethodOnCart

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

@@ -45,12 +45,12 @@ public function __construct(
      * Get cart for user
      *
      * @param string $cartHash
-     * @param int|null $userId
+     * @param int|null $customerId
      * @return Quote
      * @throws GraphQlAuthorizationException
      * @throws GraphQlNoSuchEntityException
      */
-    public function execute(string $cartHash, ?int $userId): Quote
+    public function execute(string $cartHash, ?int $customerId): Quote
     {
         try {
             $cartId = $this->maskedQuoteIdToQuoteId->execute($cartHash);
@@ -69,14 +69,14 @@ public function execute(string $cartHash, ?int $userId): Quote
             );
         }
 
-        $customerId = (int)$cart->getCustomerId();
+        $cartCustomerId = (int)$cart->getCustomerId();
 
         /* Guest cart, allow operations */
-        if (!$customerId) {
+        if (!$cartCustomerId && null === $customerId) {
             return $cart;
         }
 
-        if ($customerId !== $userId) {
+        if ($cartCustomerId !== $customerId) {
             throw new GraphQlAuthorizationException(
                 __(
                     'The current user cannot perform operations on cart "%masked_cart_id"',

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

@@ -0,0 +1,42 @@
+<?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\Exception\LocalizedException;
+use Magento\Framework\GraphQl\Config\Element\Field;
+use Magento\Framework\GraphQl\Query\ResolverInterface;
+use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
+
+/**
+ * @inheritdoc
+ */
+class SelectedPaymentMethod implements ResolverInterface
+{
+    /**
+     * @inheritdoc
+     */
+    public function resolve(Field $field, $context, ResolveInfo $info, array $value = null, array $args = null)
+    {
+        if (!isset($value['model'])) {
+            throw new LocalizedException(__('"model" value should be specified'));
+        }
+
+        /** @var \Magento\Quote\Model\Quote $cart */
+        $cart = $value['model'];
+
+        $payment = $cart->getPayment();
+        if (!$payment) {
+            return [];
+        }
+
+        return [
+            'code' => $payment->getMethod(),
+            'purchase_order_number' => $payment->getPoNumber(),
+        ];
+    }
+}

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

@@ -0,0 +1,108 @@
+<?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\Exception\LocalizedException;
+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\Framework\Stdlib\ArrayManager;
+use Magento\Quote\Api\Data\PaymentInterface;
+use Magento\QuoteGraphQl\Model\Cart\GetCartForUser;
+use Magento\Quote\Api\Data\PaymentInterfaceFactory;
+use Magento\Quote\Api\PaymentMethodManagementInterface;
+
+/**
+ * Mutation resolver for setting payment method for shopping cart
+ */
+class SetPaymentMethodOnCart implements ResolverInterface
+{
+    /**
+     * @var GetCartForUser
+     */
+    private $getCartForUser;
+
+    /**
+     * @var ArrayManager
+     */
+    private $arrayManager;
+
+    /**
+     * @var PaymentMethodManagementInterface
+     */
+    private $paymentMethodManagement;
+
+    /**
+     * @var PaymentInterfaceFactory
+     */
+    private $paymentFactory;
+
+    /**
+     * @param GetCartForUser $getCartForUser
+     * @param ArrayManager $arrayManager
+     * @param PaymentMethodManagementInterface $paymentMethodManagement
+     * @param PaymentInterfaceFactory $paymentFactory
+     */
+    public function __construct(
+        GetCartForUser $getCartForUser,
+        ArrayManager $arrayManager,
+        PaymentMethodManagementInterface $paymentMethodManagement,
+        PaymentInterfaceFactory $paymentFactory
+    ) {
+        $this->getCartForUser = $getCartForUser;
+        $this->arrayManager = $arrayManager;
+        $this->paymentMethodManagement = $paymentMethodManagement;
+        $this->paymentFactory = $paymentFactory;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function resolve(Field $field, $context, ResolveInfo $info, array $value = null, array $args = null)
+    {
+        $maskedCartId = (string)$this->arrayManager->get('input/cart_id', $args);
+        if (!$maskedCartId) {
+            throw new GraphQlInputException(__('Required parameter "cart_id" is missing'));
+        }
+
+        $paymentMethod = $this->arrayManager->get('input/payment_method', $args);
+        if (!$paymentMethod) {
+            throw new GraphQlInputException(__('Required parameter "payment_method" is missing'));
+        }
+
+        $paymentMethodCode = (string) $this->arrayManager->get('input/payment_method/code', $args);
+        if (!$paymentMethodCode) {
+            throw new GraphQlInputException(__('Required parameter payment "code" is missing'));
+        }
+
+        $poNumber = $this->arrayManager->get('input/payment_method/purchase_order_number', $args);
+
+        $cart = $this->getCartForUser->execute($maskedCartId, $context->getUserId());
+        $payment = $this->paymentFactory->create([
+            'data' => [
+                PaymentInterface::KEY_METHOD => $paymentMethodCode,
+                PaymentInterface::KEY_PO_NUMBER => $poNumber,
+                PaymentInterface::KEY_ADDITIONAL_DATA => [],
+            ]
+        ]);
+
+        try {
+            $this->paymentMethodManagement->set($cart->getId(), $payment);
+        } catch (LocalizedException $e) {
+            throw new GraphQlInputException(__($e->getMessage()));
+        }
+
+        return [
+            'cart' => [
+                'cart_id' => $maskedCartId,
+                'model' => $cart,
+            ],
+        ];
+    }
+}

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

@@ -7,6 +7,7 @@
 
 namespace Magento\QuoteGraphQl\Model\Resolver;
 
+use Magento\Framework\Exception\LocalizedException;
 use Magento\Framework\GraphQl\Config\Element\Field;
 use Magento\Framework\GraphQl\Exception\GraphQlInputException;
 use Magento\Framework\GraphQl\Query\ResolverInterface;
@@ -67,7 +68,7 @@ public function __construct(
     public function resolve(Field $field, $context, ResolveInfo $info, array $value = null, array $args = null)
     {
         $shippingAddresses = $this->arrayManager->get('input/shipping_addresses', $args);
-        $maskedCartId = (string) $this->arrayManager->get('input/cart_id', $args);
+        $maskedCartId = (string)$this->arrayManager->get('input/cart_id', $args);
 
         if (!$maskedCartId) {
             throw new GraphQlInputException(__('Required parameter "cart_id" is missing'));
@@ -79,7 +80,11 @@ public function resolve(Field $field, $context, ResolveInfo $info, array $value
 
         $cart = $this->getCartForUser->execute($maskedCartId, $context->getUserId());
 
-        $this->setShippingAddressesOnCart->execute($context, $cart, $shippingAddresses);
+        try {
+            $this->setShippingAddressesOnCart->execute($context, $cart, $shippingAddresses);
+        } catch (LocalizedException $e) {
+            throw new GraphQlInputException(__($e->getMessage()));
+        }
 
         return [
             'cart' => [

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

@@ -14,6 +14,7 @@ type Mutation {
     setShippingAddressesOnCart(input: SetShippingAddressesOnCartInput): SetShippingAddressesOnCartOutput @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\SetShippingAddressesOnCart")
     setBillingAddressOnCart(input: SetBillingAddressOnCartInput): SetBillingAddressOnCartOutput @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\SetBillingAddressOnCart")
     setShippingMethodsOnCart(input: SetShippingMethodsOnCartInput): SetShippingMethodsOnCartOutput @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\SetShippingMethodsOnCart")
+    setPaymentMethodOnCart(input: SetPaymentMethodOnCartInput): SetPaymentMethodOnCartOutput @resolver(class: "Magento\\QuoteGraphQl\\Model\\Resolver\\SetPaymentMethodOnCart")
 }
 
 input AddSimpleProductsToCartInput {
@@ -102,6 +103,24 @@ input ShippingMethodForAddressInput {
     method_code: String!
 }
 
+input SetPaymentMethodOnCartInput {
+    cart_id: String!
+    payment_method: PaymentMethodInput!
+}
+
+input PaymentMethodInput {
+    code: String! @doc(description:"Payment method code")
+    purchase_order_number: String @doc(description:"Purchase order number")
+    additional_data: PaymentMethodAdditionalDataInput
+}
+
+input PaymentMethodAdditionalDataInput {
+}
+
+type SetPaymentMethodOnCartOutput {
+    cart: Cart!
+}
+
 type SetBillingAddressOnCartOutput {
     cart: Cart!
 }
@@ -124,7 +143,8 @@ type Cart {
     applied_coupon: AppliedCoupon
     shipping_addresses: [CartAddress]! @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\ShippingAddresses")
     billing_address: CartAddress! @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\BillingAddress")
-    available_payment_methods : [PaymentMethod]  @resolver(class: "Magento\\QuoteGraphQl\\Model\\Resolver\\AvailablePaymentMethods") @doc(description: "Available payment methods")
+    available_payment_methods : [AvailablePaymentMethod]  @resolver(class: "Magento\\QuoteGraphQl\\Model\\Resolver\\AvailablePaymentMethods") @doc(description: "Available payment methods")
+    selected_payment_method: SelectedPaymentMethod @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\SelectedPaymentMethod")
 }
 
 type CartAddress {
@@ -139,8 +159,8 @@ type CartAddress {
     country: CartAddressCountry
     telephone: String
     address_type: AdressTypeEnum
-    selected_shipping_method: SelectedShippingMethod
     available_shipping_methods: [AvailableShippingMethod] @resolver(class: "\\Magento\\QuoteGraphQl\\Model\\Resolver\\ShippingAdress\\AvailableShippingMethods")
+    selected_shipping_method: SelectedShippingMethod
     items_weight: Float
     customer_notes: String
     cart_items: [CartItemQuantity]
@@ -177,11 +197,20 @@ type AvailableShippingMethod {
     price_incl_tax: Float!
 }
 
-type PaymentMethod {
+type AvailablePaymentMethod {
     code: String @doc(description: "The payment method code")
     title: String @doc(description: "The payment method title.")
 }
 
+type SelectedPaymentMethod {
+    code: String @doc(description: "The payment method code")
+    purchase_order_number: String @doc(description: "The purchase order number.")
+    additional_data: SelectedPaymentMethodAdditionalData
+}
+
+type SelectedPaymentMethodAdditionalData {
+}
+
 enum AdressTypeEnum {
     SHIPPING
     BILLING

composer.json

@@ -109,6 +109,7 @@
         "magento/module-backend": "*",
         "magento/module-backup": "*",
         "magento/module-braintree": "*",
+        "magento/module-braintree-graph-ql": "*",
         "magento/module-bundle": "*",
         "magento/module-bundle-graph-ql": "*",
         "magento/module-bundle-import-export": "*",