Support older input formats for building a schema

CHANGELOG.md

@@ -8,6 +8,8 @@ The version headers in this history reflect the versions of Apollo Server itself
 
 - _Nothing yet!_
 
+- `@apollo/federation`: `buildFederatedSchema`'s `typeDefs` parameter now accepts arrays of `DocumentNode`s (i.e. type definitions wrapped in `gql`) and `resolvers` to make the migration from a single service into a federated service easier for teams previously utilizing this pattern. [PR #3188](https://github.com/apollographql/apollo-server/pull/3188)
+
 ### v2.8.2
 
 > [See complete versioning details.](https://github.com/apollographql/apollo-server/commit/99f78c6782bce170186ba6ef311182a8c9f281b7)

packages/apollo-federation/src/service/__tests__/buildFederatedSchema.test.ts

@@ -1,5 +1,5 @@
 import gql from 'graphql-tag';
-import { Kind, graphql } from 'graphql';
+import { Kind, graphql, DocumentNode, execute } from 'graphql';
 import { buildFederatedSchema } from '../buildFederatedSchema';
 import { typeSerializer } from '../../snapshotSerializers';
 
@@ -478,3 +478,126 @@ extend type User @key(fields: "email") {
     });
   });
 });
+
+describe('legacy interface', () => {
+  const resolvers = {
+    Query: {
+      product: () => ({}),
+    },
+    Product: {
+      upc: () => '1234',
+      price: () => 10,
+    },
+  };
+  const typeDefs: DocumentNode[] = [
+    gql`
+      type Query {
+        product: Product
+      }
+      type Product @key(fields: "upc") {
+        upc: String!
+        name: String
+      }
+    `,
+    gql`
+      extend type Product {
+        price: Int
+      }
+    `,
+  ];
+  it('allows legacy schema module interface as an input with an array of typeDefs and resolvers', async () => {
+    const schema = buildFederatedSchema({ typeDefs, resolvers });
+    expect(schema.getType('_Entity')).toMatchInlineSnapshot(
+      `union _Entity = Product`,
+    );
+    expect(
+      await execute(
+        schema,
+        gql`
+          {
+            product {
+              price
+              upc
+            }
+          }
+        `,
+      ),
+    ).toEqual({
+      data: {
+        product: { upc: '1234', price: 10 },
+      },
+    });
+  });
+  it('allows legacy schema module interface as a single module', async () => {
+    const schema = buildFederatedSchema({
+      typeDefs: gql`
+        type Query {
+          product: Product
+        }
+        type Product @key(fields: "upc") {
+          upc: String!
+          name: String
+          price: Int
+        }
+      `,
+      resolvers,
+    });
+    expect(schema.getType('_Entity')).toMatchInlineSnapshot(
+      `union _Entity = Product`,
+    );
+    expect(
+      await execute(
+        schema,
+        gql`
+          {
+            product {
+              price
+              upc
+            }
+          }
+        `,
+      ),
+    ).toEqual({
+      data: {
+        product: { upc: '1234', price: 10 },
+      },
+    });
+  });
+  it('allows legacy schema module interface as a single module without resolvers', async () => {
+    const schema = buildFederatedSchema({
+      typeDefs: gql`
+        type Query {
+          product: Product
+        }
+        type Product @key(fields: "upc") {
+          upc: String!
+          name: String
+          price: Int
+        }
+      `,
+    });
+    expect(schema.getType('Product')).toMatchInlineSnapshot(`
+type Product {
+  upc: String!
+  name: String
+  price: Int
+}
+`);
+    expect(schema.getType('_Entity')).toMatchInlineSnapshot(
+      `union _Entity = Product`,
+    );
+  });
+  it('allows legacy schema module interface as a simple array of documents', async () => {
+    const schema = buildFederatedSchema({ typeDefs });
+    expect(schema.getType('Product')).toMatchInlineSnapshot(`
+type Product {
+  upc: String!
+  name: String
+  price: Int
+}
+`);
+    expect(schema.getType('_Entity')).toMatchInlineSnapshot(
+      `union _Entity = Product`,
+    );
+  });
+});

packages/apollo-federation/src/service/buildFederatedSchema.ts

@@ -13,6 +13,7 @@ import {
   GraphQLSchemaModule,
   modulesFromSDL,
   addResolversToSchema,
+  GraphQLResolverMap,
 } from 'apollo-graphql';
 import federationDirectives, { typeIncludesDirective } from '../directives';
 
@@ -22,10 +23,43 @@ import { printSchema } from './printFederatedSchema';
 
 import 'apollo-server-env';
 
+type LegacySchemaModule = {
+  typeDefs: DocumentNode | DocumentNode[];
+  resolvers?: GraphQLResolverMap<any>;
+};
+
 export function buildFederatedSchema(
-  modulesOrSDL: (GraphQLSchemaModule | DocumentNode)[] | DocumentNode,
+  modulesOrSDL:
+    | (GraphQLSchemaModule | DocumentNode)[]
+    | DocumentNode
+    | LegacySchemaModule,
 ): GraphQLSchema {
-  const modules = modulesFromSDL(modulesOrSDL);
+  // ApolloServer supports passing an array of DocumentNode along with a single
+  // map of resolvers to build a schema. Long term we don't want to support this
+  // style anymore as we move towards a more structured approach to modules,
+  // however, it has tripped several teams up to not support this signature
+  // in buildFederatedSchema. Especially as teams migrate from
+  // `new ApolloServer({ typeDefs: DocumentNode[], resolvers })` to
+  // `new ApolloServer({ schema: buildFederatedSchema({ typeDefs: DocumentNode[], resolvers }) })`
+  //
+  // The last type in the union for `modulesOrSDL` supports this "legacy" input
+  // style in a simple manner (by just adding the resolvers to the first typeDefs entry)
+  //
+  let shapedModulesOrSDL: (GraphQLSchemaModule | DocumentNode)[] | DocumentNode;
+  if ('typeDefs' in modulesOrSDL) {
+    const { typeDefs, resolvers } = modulesOrSDL;
+    const augmentedTypeDefs = Array.isArray(typeDefs) ? typeDefs : [typeDefs];
+    shapedModulesOrSDL = augmentedTypeDefs.map((typeDefs, i) => {
+      const module: GraphQLSchemaModule = { typeDefs };
+      // add the resolvers to the first "module" in the array
+      if (i === 0 && resolvers) module.resolvers = resolvers;
+      return module;
+    });
+  } else {
+    shapedModulesOrSDL = modulesOrSDL;
+  }
+
+  const modules = modulesFromSDL(shapedModulesOrSDL);
 
   let schema = buildSchemaFromSDL(
     modules,