Merge custom directives with federated schema

lib/index.js

@@ -3,7 +3,7 @@
 const graphql = require('graphql');
 const gql = require('graphql-tag');
 const { buildFederatedSchema } = require('@apollo/federation');
-const { makeExecutableSchema, addMockFunctionsToSchema } = require('graphql-tools');
+const { makeExecutableSchema, addMockFunctionsToSchema, mergeSchemas } = require('graphql-tools');
 const { mergeResolvers, mergeTypeDefs } = require('graphql-toolkit');
 const { getImportedResolvers, transformResolvers, wrapResolvers } = require('./resolvers');
 const { wrapContext, createContext } = require('./context');
@@ -112,6 +112,19 @@ class GraphQLComponent {
     return graphql.execute({ document, schema: this.schema, rootValue: root, contextValue: context, variableValues: variables });
   }
 
+  makeFederatedSchemaWithDirectives({typeDefs, resolvers, schemaDirectives}) {
+    const federatedSchema = buildFederatedSchema({
+      typeDefs,
+      resolvers
+    });
+
+    return mergeSchemas({
+      schemas: [federatedSchema],
+      schemaDirectives,
+      mergeDirectives: true
+    });
+  } 
+
   get schema() {
     if (this._schema) {
       return this._schema;
@@ -121,7 +134,7 @@ class GraphQLComponent {
     const resolvers = this._mergedResolvers;
     const schemaDirectives = this._mergedDirectives;
 
-    const makeSchema = this._federation ? buildFederatedSchema : makeExecutableSchema;
+    const makeSchema = this._federation ? this.makeFederatedSchemaWithDirectives : makeExecutableSchema;
 
     const schema = makeSchema({
       typeDefs,

test/test-federation.js

@@ -2,16 +2,24 @@
 
 const Test = require('tape');
 const GraphQLComponent = require('../lib');
+const {SchemaDirectiveVisitor} = require('apollo-server');
 
 Test('federated schema', (t) => {
 
-  t.plan(1);
+  class CustomDirective extends SchemaDirectiveVisitor {
+    // required for our dummy "custom" directive (ie. implement the SchemaDirectiveVisitor interface)
+    visitFieldDefinition() {
+      return;
+    }
+  }
 
   const component = new GraphQLComponent({
     types: [
       `
+      directive @custom on FIELD_DEFINITION
+
       type Query {
-        property(id: ID!): Property
+        property(id: ID!): Property @custom
       }
       type Property @key(fields: "id") {
         id: ID!
@@ -34,10 +42,20 @@ Test('federated schema', (t) => {
         }
       }
     },
+    directives: { custom: CustomDirective },
     federation: true
   });
 
-  t.doesNotThrow(() => {
-    component.schema;
-  }, 'can return a buildFederatedSchema schema');
+  t.test('create federated schema', (t) => {
+    t.plan(1);
+    t.doesNotThrow(() => {
+      component.schema;
+    }, 'can return a buildFederatedSchema schema');
+  });
+
+  t.test('custom directive added to federated schema', (t) => {
+    t.plan(1);
+    const {schema: {_directives: schemaDirectives}} = component;
+    t.equals(schemaDirectives.filter((directive) => directive.name === 'custom').length, 1, `federated schema has '@custom' directive`);
+  });
 });