Fixes #1617: Federation Enum not parsing value 0 (#1618)

* Fixes #1617
Updated buildSchemaFromSDL to handle Enums with a value of 0. Previously, when an enum had a value of 0, the name would be used as the enum value.

Author: ShadyKutz

CHANGELOG.md

@@ -15,7 +15,7 @@
 - `apollo-env`
   - <First `apollo-env` related entry goes here>
 - `apollo-graphql`
-  - <First `apollo-graphql` related entry goes here>
+  - [#1618] Fixes an issue when enums with a value of 0 fail to resolve when using a Federated Schema (https://github.com/apollographql/apollo-tooling/pull/1618)
 - `apollo-language-server`
   - <First `apollo-language-server` related entry goes here>
 - `apollo-tools`

packages/apollo-graphql/src/schema/__tests__/buildSchemaFromSDL.test.ts

@@ -503,5 +503,52 @@ type MutationRoot {
       expect(colorEnum.getValue("RED")!.value).toBe("#f00");
       expect(mockResolver).toBeCalledWith(undefined, { borderColor: "#f00" });
     });
+
+    it(`should add resolvers to enum types with 0 value`, () => {
+      const typeDefs = gql`
+        enum CustomerType {
+          EXISTING
+          NEW
+        }
+
+        type Query {
+          existingCustomer: CustomerType
+          newCustomer: CustomerType
+        }
+      `;
+
+      const resolvers = {
+        CustomerType: {
+          EXISTING: 0,
+          NEW: 1
+        },
+        Query: {
+          existingCustomer: () => 0,
+          newCustomer: () => 1
+        }
+      };
+
+      const schema = buildSchemaFromSDL([{ typeDefs, resolvers }]);
+      const customerTypeEnum = schema.getType(
+        "CustomerType"
+      ) as GraphQLEnumType;
+
+      let result = execute(
+        schema,
+        gql`
+          query {
+            existingCustomer
+            newCustomer
+          }
+        `
+      );
+
+      expect((result as ExecutionResult).data!.existingCustomer).toBe(
+        "EXISTING"
+      );
+      expect(customerTypeEnum.getValue("EXISTING")!.value).toBe(0);
+      expect((result as ExecutionResult).data!.newCustomer).toBe("NEW");
+      expect(customerTypeEnum.getValue("NEW")!.value).toBe(1);
+    });
   });
 });

packages/apollo-graphql/src/schema/buildSchemaFromSDL.ts

@@ -237,7 +237,10 @@ export function addResolversToSchema(
       const values = type.getValues();
       const newValues: { [key: string]: GraphQLEnumValue } = {};
       values.forEach(value => {
-        const newValue = (fieldConfigs as any)[value.name] || value.name;
+        let newValue = (fieldConfigs as any)[value.name];
+        if (newValue === undefined) {
+          newValue = value.name;
+        }
         newValues[value.name] = {
           value: newValue,
           deprecationReason: value.deprecationReason,