ENGCOM-5913: GraphQL-893 improved strict typing in SelectedShippingMethod #900

 - Merge Pull Request magento/graphql-ce#900 from sergiy-v/graphql-ce:893-improve-strict-typing-in-SelectedShippingMethod
 - Merged commits:
   1. 830e0c1
   2. 945a1a7
   3. 9e6adc8
   4. 891146c

Author: magento-engcom-team

app/code/Magento/QuoteGraphQl/Model/Resolver/ShippingAddress/SelectedShippingMethod.php

@@ -31,36 +31,37 @@ public function resolve(Field $field, $context, ResolveInfo $info, array $value
         /** @var Address $address */
         $address = $value['model'];
         $rates = $address->getAllShippingRates();
-        $carrierTitle = null;
-        $methodTitle = null;
+        $carrierTitle = '';
+        $methodTitle = '';
 
-        if (count($rates) > 0 && !empty($address->getShippingMethod())) {
-            list($carrierCode, $methodCode) = explode('_', $address->getShippingMethod(), 2);
+        if (!count($rates) || empty($address->getShippingMethod())) {
+            return null;
+        }
 
-            /** @var Rate $rate */
-            foreach ($rates as $rate) {
-                if ($rate->getCode() == $address->getShippingMethod()) {
-                    $carrierTitle = $rate->getCarrierTitle();
-                    $methodTitle = $rate->getMethodTitle();
-                    break;
-                }
-            }
+        list($carrierCode, $methodCode) = explode('_', $address->getShippingMethod(), 2);
 
-            $data = [
-                'carrier_code' => $carrierCode,
-                'method_code' => $methodCode,
-                'carrier_title' => $carrierTitle,
-                'method_title' => $methodTitle,
-                'amount' => [
-                    'value' => $address->getShippingAmount(),
-                    'currency' => $address->getQuote()->getQuoteCurrencyCode(),
-                ],
-                /** @deprecated The field should not be used on the storefront */
-                'base_amount' => null,
-            ];
-        } else {
-            $data = null;
+        /** @var Rate $rate */
+        foreach ($rates as $rate) {
+            if ($rate->getCode() == $address->getShippingMethod()) {
+                $carrierTitle = $rate->getCarrierTitle();
+                $methodTitle = $rate->getMethodTitle();
+                break;
+            }
         }
+
+        $data = [
+            'carrier_code' => $carrierCode,
+            'method_code' => $methodCode,
+            'carrier_title' => $carrierTitle,
+            'method_title' => $methodTitle,
+            'amount' => [
+                'value' => $address->getShippingAmount(),
+                'currency' => $address->getQuote()->getQuoteCurrencyCode(),
+            ],
+            /** @deprecated The field should not be used on the storefront */
+            'base_amount' => null,
+        ];
+
         return $data;
     }
 }

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

@@ -242,11 +242,11 @@ type CartAddressCountry {
 }
 
 type SelectedShippingMethod {
-    carrier_code: String
-    method_code: String
-    carrier_title: String
-    method_title: String
-    amount: Money
+    carrier_code: String!
+    method_code: String!
+    carrier_title: String!
+    method_title: String!
+    amount: Money!
     base_amount: Money @deprecated(reason: "The field should not be used on the storefront")
 }
 

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

@@ -133,12 +133,7 @@ public function testGetGetSelectedShippingMethodIfShippingMethodIsNotSet()
 
         $shippingAddress = current($response['cart']['shipping_addresses']);
         self::assertArrayHasKey('selected_shipping_method', $shippingAddress);
-
-        self::assertNull($shippingAddress['selected_shipping_method']['carrier_code']);
-        self::assertNull($shippingAddress['selected_shipping_method']['method_code']);
-        self::assertNull($shippingAddress['selected_shipping_method']['carrier_title']);
-        self::assertNull($shippingAddress['selected_shipping_method']['method_title']);
-        self::assertNull($shippingAddress['selected_shipping_method']['amount']);
+        self::assertNull($shippingAddress['selected_shipping_method']);
     }
 
     /**