Rework value type implementation

This commit implements value types as a core part of composition
and query planning. With this work, we now:
* build another metadata map for tracking value types
* attach value type metadata to schema type nodes
* make query planning decisions based on value type metadata

packages/apollo-federation/src/composition/__tests__/composeAndValidate.test.ts

@@ -1,6 +1,6 @@
 import { composeAndValidate } from '../composeAndValidate';
 import gql from 'graphql-tag';
-import { GraphQLObjectType } from 'graphql';
+import { GraphQLObjectType, DocumentNode } from 'graphql';
 import {
   astSerializer,
   typeSerializer,
@@ -276,65 +276,111 @@ it('errors on invalid usages of default operation names', () => {
   `);
 });
 
-describe('value types integration tests', () => {
-  it('handles valid value types correctly', () => {
-    const duplicatedValueTypes = gql`
-      scalar Date
+describe('composition of value types', () => {
+  function getSchemaWithValueType(valueType: DocumentNode) {
+    const serviceA = {
+      typeDefs: gql`
+        ${valueType}
 
-      union CatalogItem = Couch | Mattress
+        type Query {
+          filler: String
+        }
+      `,
+      name: 'serviceA',
+    };
 
-      interface Product {
-        sku: ID!
-      }
+    const serviceB = {
+      typeDefs: valueType,
+      name: 'serviceB',
+    };
 
-      input NewProductInput {
-        sku: ID!
-        type: CatalogItemEnum
-      }
+    return composeAndValidate([serviceA, serviceB]);
+  }
 
-      enum CatalogItemEnum {
-        COUCH
-        MATTRESS
-      }
+  describe('success', () => {
+    it('scalars', () => {
+      const { errors, schema } = getSchemaWithValueType(
+        gql`
+          scalar Date
+        `,
+      );
+      expect(errors).toHaveLength(0);
+      expect(schema.getType('Date')).toMatchInlineSnapshot(`scalar Date`);
+    });
 
-      type Couch implements Product {
+    it('unions and object types', () => {
+      const { errors, schema } = getSchemaWithValueType(
+        gql`
+          union CatalogItem = Couch | Mattress
+
+          type Couch {
+            sku: ID!
+            material: String!
+          }
+
+          type Mattress {
+            sku: ID!
+            size: String!
+          }
+        `,
+      );
+      expect(errors).toHaveLength(0);
+      expect(schema.getType('CatalogItem')).toMatchInlineSnapshot(
+        `union CatalogItem = Couch | Mattress`,
+      );
+      expect(schema.getType('Couch')).toMatchInlineSnapshot(`
+      type Couch {
         sku: ID!
         material: String!
       }
+    `);
+    });
 
-      type Mattress implements Product {
+    it('input types', () => {
+      const { errors, schema } = getSchemaWithValueType(gql`
+        input NewProductInput {
+          sku: ID!
+          type: String
+        }
+      `);
+      expect(errors).toHaveLength(0);
+      expect(schema.getType('NewProductInput')).toMatchInlineSnapshot(`
+      input NewProductInput {
         sku: ID!
-        size: String!
+        type: String
       }
-    `;
+    `);
+    });
 
-    const serviceA = {
-      typeDefs: gql`
-        type Query {
-          product: Product
+    it('interfaces', () => {
+      const { errors, schema } = getSchemaWithValueType(gql`
+        interface Product {
+          sku: ID!
         }
-        ${duplicatedValueTypes}
-      `,
-      name: 'serviceA',
-    };
+      `);
+      expect(errors).toHaveLength(0);
+      expect(schema.getType('Product')).toMatchInlineSnapshot(`
+      interface Product {
+        sku: ID!
+      }
+    `);
+    });
 
-    const serviceB = {
-      typeDefs: gql`
-        type Query {
-          topProducts: [Product]
+    it('enums', () => {
+      const { errors, schema } = getSchemaWithValueType(gql`
+        enum CatalogItemEnum {
+          COUCH
+          MATTRESS
         }
-        ${duplicatedValueTypes}
-      `,
-      name: 'serviceB',
-    };
-
-    const { errors, schema } = composeAndValidate([serviceA, serviceB]);
-
-    // A value type doesn't need any federation metadata to resolve
-    const couchType = schema.getType('Couch');
-    expect(couchType.federation.serviceName).toEqual(null);
-
-    expect(errors).toHaveLength(0);
+      `);
+      expect(errors).toHaveLength(0);
+      expect(schema.getType('CatalogItemEnum')).toMatchInlineSnapshot(`
+      enum CatalogItemEnum {
+        COUCH
+        MATTRESS
+      }
+    `);
+    });
   });
 
   describe('errors', () => {

packages/apollo-federation/src/composition/compose.ts

@@ -27,6 +27,7 @@ import {
   parseSelections,
   mapFieldNamesToServiceName,
   stripExternalFieldsFromTypeDefs,
+  diffTypeNodes,
 } from './utils';
 import {
   ServiceDefinition,
@@ -99,6 +100,14 @@ interface TypeToServiceMap {
 export interface KeyDirectivesMap {
   [typeName: string]: ServiceNameToKeyDirectivesMap;
 }
+
+/**
+ * A map for tracking which types have been determined to be a value type, a type
+ * shared across at least 2 services.
+ */
+export interface ValueTypesMap {
+  [typeName: string]: boolean;
+}
 /**
  * Loop over each service and process its typeDefs (`definitions`)
  * - build up typeToServiceMap
@@ -110,6 +119,7 @@ export function buildMapsFromServiceList(serviceList: ServiceDefinition[]) {
   const typeToServiceMap: TypeToServiceMap = Object.create(null);
   const externalFields: ExternalFieldDefinition[] = [];
   const keyDirectivesMap: KeyDirectivesMap = Object.create(null);
+  const valueTypesMap: ValueTypesMap = Object.create(null);
 
   for (const { typeDefs, name: serviceName } of serviceList) {
     // Build a new SDL with @external fields removed, as well as information about
@@ -170,9 +180,27 @@ export function buildMapsFromServiceList(serviceList: ServiceDefinition[]) {
 
         /**
          * If this type already exists in the definitions map, push this definition to the array (newer defs
-         * take precedence). If not, create the definitions array and add it to the definitionsMap.
+         * take precedence). If the types are determined to be identical, add the type name
+         * to the valueTypesMap.
+         *
+         * If not, create the definitions array and add it to the definitionsMap.
          */
         if (definitionsMap[typeName]) {
+          const { name, kind, fields, unionTypes } = diffTypeNodes(
+            definitionsMap[typeName][definitionsMap[typeName].length - 1],
+            definition,
+          );
+
+          const isValueType =
+            name.length === 0 &&
+            kind.length === 0 &&
+            Object.keys(fields).length === 0 &&
+            Object.keys(unionTypes).length === 0;
+
+          if (isValueType) {
+            valueTypesMap[typeName] = true;
+          }
+
           definitionsMap[typeName].push({ ...definition, serviceName });
         } else {
           definitionsMap[typeName] = [{ ...definition, serviceName }];
@@ -260,6 +288,7 @@ export function buildMapsFromServiceList(serviceList: ServiceDefinition[]) {
     extensionsMap,
     externalFields,
     keyDirectivesMap,
+    valueTypesMap,
   };
 }
 
@@ -300,19 +329,21 @@ export function buildSchemaFromDefinitionsAndExtensions({
 }
 
 /**
- * Using the typeToServiceMap, augment the passed in `schema` to add `federation` metadata to the types and
- * fields
+ * Using the various information we've collected about the schema, augment the
+ * `schema` itself with `federation` metadata to the types and fields
  */
 export function addFederationMetadataToSchemaNodes({
   schema,
   typeToServiceMap,
   externalFields,
   keyDirectivesMap,
+  valueTypesMap,
 }: {
   schema: GraphQLSchema;
   typeToServiceMap: TypeToServiceMap;
   externalFields: ExternalFieldDefinition[];
   keyDirectivesMap: KeyDirectivesMap;
+  valueTypesMap: ValueTypesMap;
 }) {
   for (const [
     typeName,
@@ -329,6 +360,7 @@ export function addFederationMetadataToSchemaNodes({
       ...(keyDirectivesMap[typeName] && {
         keys: keyDirectivesMap[typeName],
       }),
+      isValueType: Boolean(valueTypesMap[typeName]),
     };
 
     // For object types, add metadata for all the @provides directives from its fields
@@ -420,6 +452,7 @@ export function composeServices(services: ServiceDefinition[]) {
     extensionsMap,
     externalFields,
     keyDirectivesMap,
+    valueTypesMap,
   } = buildMapsFromServiceList(services);
 
   let { schema, errors } = buildSchemaFromDefinitionsAndExtensions({
@@ -465,6 +498,7 @@ export function composeServices(services: ServiceDefinition[]) {
     typeToServiceMap,
     externalFields,
     keyDirectivesMap,
+    valueTypesMap,
   });
 
   /**

packages/apollo-federation/src/composition/types.ts

@@ -23,6 +23,7 @@ export interface FederationType {
   externals?: {
     [serviceName: string]: ExternalFieldDefinition[];
   };
+  isValueType?: boolean;
 }
 
 export interface FederationField {

packages/apollo-gateway/src/__tests__/__fixtures__/schemas/books.ts

@@ -1,5 +1,6 @@
 import gql from 'graphql-tag';
 import { GraphQLResolverMap } from 'apollo-graphql';
+import { log } from 'util';
 
 export const name = 'books';
 export const typeDefs = gql`
@@ -27,14 +28,23 @@ export const typeDefs = gql`
     title: String
     year: Int
     similarBooks: [Book]!
-    metadata: [KeyValue]
+    metadata: [MetadataOrError]
   }
 
   # Value type
   type KeyValue {
     key: String!
     value: String!
   }
+
+  # Value type
+  type Error {
+    code: Int
+    message: String
+  }
+
+  # Value type
+  union MetadataOrError = KeyValue | Error
 `;
 
 const libraries = [{ id: '1', name: 'NYC Public Library' }];
@@ -49,7 +59,10 @@ const books = [
     isbn: '0136291554',
     title: 'Object Oriented Software Construction',
     year: 1997,
-    metadata: [{ key: 'Condition', value: 'used' }],
+    metadata: [
+      { key: 'Condition', value: 'used' },
+      { code: '401', message: 'Unauthorized' },
+    ],
   },
   {
     isbn: '0201633612',
@@ -105,4 +118,9 @@ export const resolvers: GraphQLResolverMap<any> = {
       return libraries.find(library => library.id === id);
     },
   },
+  MetadataOrError: {
+    __resolveType(object) {
+      return 'key' in object ? 'KeyValue' : 'Error';
+    },
+  },
 };

packages/apollo-gateway/src/__tests__/__fixtures__/schemas/product.ts

@@ -32,7 +32,7 @@ export const typeDefs = gql`
     name: String
     price: String
     brand: Brand
-    metadata: [KeyValue]
+    metadata: [MetadataOrError]
   }
 
   extend type Book implements Product @key(fields: "isbn") {
@@ -55,6 +55,15 @@ export const typeDefs = gql`
     key: String!
     value: String!
   }
+
+  # Value type
+  type Error {
+    code: Int
+    message: String
+  }
+
+  # Value type
+  union MetadataOrError = KeyValue | Error
 `;
 
 const products = [
@@ -158,4 +167,9 @@ export const resolvers: GraphQLResolverMap<any> = {
       return products.slice(0, args.first);
     },
   },
+  MetadataOrError: {
+    __resolveType(object) {
+      return 'key' in object ? 'KeyValue' : 'Error';
+    },
+  },
 };