Add polymorphic types from extensions to the schema (#830)

Co-authored-by: Benjie Gillam <benjie@jemjie.com>

Author: mgagliardo91

packages/graphile-utils/__tests__/ExtendSchemaPlugin.test.js

@@ -817,6 +817,12 @@ it("supports interfaces and unions", async () => {
           c: Int!
         }
 
+        # A child type that has no explicit references
+        type D implements Named {
+          name: String!
+          d: Int!
+        }
+
         union ABC = A | B | C
         extend type Query {
           abc: [ABC!]
@@ -832,6 +838,9 @@ it("supports interfaces and unions", async () => {
         extend type B {
           nameLanguage: String
         }
+        extend type D {
+          nameLanguage: String
+        }
       `,
       resolvers: {
         Query: {
@@ -843,6 +852,7 @@ it("supports interfaces and unions", async () => {
           named: () => [
             { name: "A-one", a: 1, nameLanguage: "en" },
             { name: "B-two", b: 2, nameLanguage: "en" },
+            { name: "D-three", d: 3, nameLanguage: "en" },
           ],
         },
         ABC: {
@@ -857,6 +867,7 @@ it("supports interfaces and unions", async () => {
           __resolveType(obj) {
             if (obj.a != null) return "A";
             if (obj.b != null) return "B";
+            if (obj.d != null) return "D";
             return null;
           },
         },
@@ -894,6 +905,9 @@ it("supports interfaces and unions", async () => {
           ... on B {
             b
           }
+          ... on D {
+            d
+          }
         }
       }
     `

packages/graphile-utils/__tests__/__snapshots__/ExtendSchemaPlugin-pg.test.js.snap

@@ -2531,16 +2531,16 @@ type Mutation {
   ): RegisterUserPayload
 }
 
-type RegisterUserPayload {
-  user: User
-}
-
 input RegisterUserInput {
   name: String!
   email: String!
   bio: String
 }
 
+type RegisterUserPayload {
+  user: User
+}
+
 `;
 
 exports[`allows adding a simple mutation field to PG schema 2`] = `

packages/graphile-utils/__tests__/__snapshots__/ExtendSchemaPlugin.test.js.snap

@@ -230,14 +230,14 @@ type Mutation {
   echo(input: EchoInput): EchoOutput
 }
 
-type EchoOutput {
+input EchoInput {
   text: String!
   int: Int
   float: Float!
   intList: [Int!]
 }
 
-input EchoInput {
+type EchoOutput {
   text: String!
   int: Int
   float: Float!
@@ -406,16 +406,14 @@ type Query {
   named: [Named!]
 }
 
-union ABC = A | B | C
-
-type A implements Named {
+interface Named {
   name: String!
-  a: Int!
   nameLanguage: String
 }
 
-interface Named {
+type A implements Named {
   name: String!
+  a: Int!
   nameLanguage: String
 }
 
@@ -429,6 +427,14 @@ type C {
   c: Int!
 }
 
+type D implements Named {
+  name: String!
+  d: Int!
+  nameLanguage: String
+}
+
+union ABC = A | B | C
+
 `;
 
 exports[`supports interfaces and unions 2`] = `
@@ -464,6 +470,12 @@ Object {
       "name": "B-two",
       "nameLanguage": "en",
     },
+    Object {
+      "__typename": "D",
+      "d": 3,
+      "name": "D-three",
+      "nameLanguage": "en",
+    },
   ],
 }
 `;

packages/graphile-utils/src/makeExtendSchemaPlugin.ts

@@ -44,6 +44,7 @@ import type {
   GraphQLDirective,
   InputObjectTypeExtensionNode,
   InterfaceTypeExtensionNode,
+  TypeDefinitionNode,
 } from "graphql";
 import { GraphileEmbed } from "./gql";
 
@@ -478,16 +479,32 @@ export default function makeExtendSchemaPlugin(
     });
 
     builder.hook("GraphQLSchema", (schema, build, _context) => {
+      const { inflection } = build;
       const {
         [`ExtendSchemaPlugin_${uniqueId}_typeExtensions`]: typeExtensions,
+        [`ExtendSchemaPlugin_${uniqueId}_newTypes`]: newTypeDefinitions,
       } = build;
+      const newTypes = newTypeDefinitions.map(
+        ({ definition }: { definition: TypeDefinitionNode }) =>
+          build.getTypeByName(definition.name.value)
+      );
+
       return {
         ...schema,
         directives: [
           ...(schema.directives || build.graphql.specifiedDirectives || []),
           ...typeExtensions.GraphQLSchema.directives,
         ],
-        types: [...(schema.types || []), ...typeExtensions.GraphQLSchema.types],
+        types: [
+          ...(schema.types || []),
+          ...[
+            build.getTypeByName(inflection.builtin("Query")),
+            build.getTypeByName(inflection.builtin("Mutation")),
+            build.getTypeByName(inflection.builtin("Subscription")),
+          ].filter(_ => _),
+          ...typeExtensions.GraphQLSchema.types,
+          ...newTypes,
+        ],
       };
     });