Add support for interface on interfaces to transformSchema

CHANGELOG.md

@@ -19,7 +19,7 @@
 - `apollo-env`
   - <First `apollo-env` related entry goes here>
 - `apollo-graphql`
-  - <First `apollo-graphql` related entry goes here>
+  - Add support for interface on interfaces to transformSchema. [PR #2456](https://github.com/apollographql/apollo-tooling/pull/2456)
 - `apollo-language-server`
   - <First `apollo-language-server` related entry goes here>
 - `apollo-tools`

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

@@ -14,10 +14,27 @@ describe("transformSchema", () => {
 
     # https://github.com/apollographql/apollo-tooling/issues/2162
     directive @test(baz: DirectiveArg) on FIELD_DEFINITION
+
+    interface FooInterface {
+      foo: String
+    }
+
+    interface BarInterface implements FooInterface {
+      foo: String
+      bar: Boolean
+    }
+
+    type FooBarBazType implements FooInterface & BarInterface {
+      foo: String
+      bar: Boolean
+      baz: Float
+    }
     `);
 
+    const originalSDL = printSchema(schema);
     const newSchema = transformSchema(schema, namedType => namedType);
 
-    expect(printSchema(newSchema)).toEqual(printSchema(schema));
+    expect(printSchema(schema)).toEqual(originalSDL);
+    expect(printSchema(newSchema)).toEqual(originalSDL);
   });
 });

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)) {