Fix/transform schema interfaces implementing interfaces

CHANGELOG.md

@@ -19,7 +19,7 @@
 - `apollo-env`
   - <First `apollo-env` related entry goes here>
 - `apollo-graphql`
-  - <First `apollo-graphql` related entry goes here>
+  - Fixed issue where `transformSchema` crashed when a schema had an interface which implements an interface [#2246](https://github.com/apollographql/apollo-tooling/pull/2246)
 - `apollo-language-server`
   - <First `apollo-language-server` related entry goes here>
 - `apollo-tools`

packages/apollo-graphql/src/schema/__tests__/transformSchema.ts

@@ -0,0 +1,29 @@
+import { transformSchema } from "../transformSchema";
+import { buildSchema } from "graphql";
+
+import astSerializer from "./snapshotSerializers/astSerializer";
+import graphQLTypeSerializer from "./snapshotSerializers/graphQLTypeSerializer";
+import selectionSetSerializer from "./snapshotSerializers/selectionSetSerializer";
+
+expect.addSnapshotSerializer(astSerializer);
+expect.addSnapshotSerializer(graphQLTypeSerializer);
+expect.addSnapshotSerializer(selectionSetSerializer);
+
+describe("transformSchema", () => {
+  it(`should handle interfaces implementing interfaces without duplicating type instances`, () => {
+    const originalSchema = buildSchema(`
+      interface A { text: String }
+      interface B implements A { text: String number: Int}`);
+
+    const schema = transformSchema(originalSchema, t => {
+      return undefined;
+    });
+
+    expect(schema.getType("B")).toMatchInlineSnapshot(`
+interface B implements A {
+  text: String
+  number: Int
+}
+`);
+  });
+});

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

@@ -72,6 +72,7 @@ export function transformSchema(
 
       return new GraphQLInterfaceType({
         ...config,
+        interfaces: () => config.interfaces.map(replaceNamedType),
         fields: () => replaceFields(config.fields)
       });
     } else if (isUnionType(type)) {