buildSchemaFromSDL - support meta fields on abstract types (#1330)

* buildSchemaFromSDL - support meta fields on abstract types

Add support for meta resolvers on abstract types.

Author: trevor-scheer

CHANGELOG.md

@@ -17,7 +17,7 @@
 - `apollo-env`
   - <First `apollo-env` related entry goes here>
 - `apollo-graphql`
-  - <First `apollo-graphql` related entry goes here>
+  - buildSchemaFromSDL - support meta fields on abstract types [#1330](https://github.com/apollographql/apollo-tooling/pull/1330)
 - `apollo-language-server`
   - <First `apollo-codegen-core` related entry goes here>
 - `apollo-tools`

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

@@ -4,7 +4,8 @@ import {
   GraphQLSchema,
   GraphQLDirective,
   DirectiveLocation,
-  GraphQLObjectType
+  GraphQLObjectType,
+  GraphQLAbstractType
 } from "graphql";
 
 import astSerializer from "./snapshotSerializers/astSerializer";
@@ -345,6 +346,7 @@ type MutationRoot {
       );
     });
   });
+
   describe(`resolvers`, () => {
     it(`should add a resolver for a field`, () => {
       const name = () => {};
@@ -372,5 +374,53 @@ type MutationRoot {
 
       expect(nameField.resolve).toEqual(name);
     });
+
+    it(`should add meta fields to abstract types`, () => {
+      const typeDefs = gql`
+        union Animal = Dog
+
+        interface Creature {
+          name: String!
+          legs: Int!
+        }
+
+        type Dog {
+          id: ID!
+        }
+
+        type Cat implements Creature {
+          meow: Boolean!
+        }
+      `;
+
+      const resolveTypeUnion = (obj: any) => {
+        return "Dog";
+      };
+
+      const resolveTypeInterface = (obj: any) => {
+        if (obj.meow) {
+          return "Cat";
+        }
+        throw Error("Couldn't resolve interface");
+      };
+
+      const resolvers = {
+        Animal: {
+          __resolveType: resolveTypeUnion
+        },
+        Creature: {
+          __resolveType: resolveTypeInterface
+        }
+      };
+
+      const schema = buildSchemaFromSDL([{ typeDefs, resolvers }]);
+      const animalUnion = schema.getType("Animal") as GraphQLAbstractType;
+      const creatureInterface = schema.getType(
+        "Creature"
+      ) as GraphQLAbstractType;
+
+      expect(animalUnion.resolveType).toBe(resolveTypeUnion);
+      expect(creatureInterface.resolveType).toBe(resolveTypeInterface);
+    });
   });
 });

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

@@ -13,7 +13,8 @@ import {
   SchemaDefinitionNode,
   SchemaExtensionNode,
   OperationTypeNode,
-  GraphQLObjectType
+  GraphQLObjectType,
+  isAbstractType
 } from "graphql";
 import { validateSDL } from "graphql/validation/validate";
 import { isDocumentNode, isNode } from "../utilities/graphql";
@@ -206,6 +207,15 @@ export function addResolversToSchema(
 ) {
   for (const [typeName, fieldConfigs] of Object.entries(resolvers)) {
     const type = schema.getType(typeName);
+
+    if (isAbstractType(type)) {
+      for (const [fieldName, fieldConfig] of Object.entries(fieldConfigs)) {
+        if (fieldName.startsWith("__")) {
+          (type as any)[fieldName.substring(2)] = fieldConfig;
+        }
+      }
+    }
+
     if (!isObjectType(type)) continue;
 
     const fieldMap = type.getFields();