Drop usage of graphql-extensions in favor of plugin API.

This commit was already implemented in the `release-3.0` branch on the
`apollo-server` repository [[Ref]], however, now that Apollo Gateway and Apollo
Federation are part of the `federation` repository, that particular commit
will likely never see the light of day!

[Ref]: apollographql/apollo-server@05f0d2f

gateway-js/package.json

@@ -29,7 +29,6 @@
     "apollo-server-env": "^2.4.5",
     "apollo-server-errors": "^2.4.2",
     "apollo-server-types": "^0.5.1",
-    "graphql-extensions": "^0.12.4",
     "loglevel": "^1.6.1",
     "make-fetch-happen": "^8.0.0",
     "pretty-format": "^26.0.0"

gateway-js/src/datasources/LocalGraphQLDataSource.ts

@@ -6,14 +6,14 @@ import {
   DocumentNode,
   parse,
 } from 'graphql';
-import { enableGraphQLExtensions } from 'graphql-extensions';
+import {
+  enablePluginsForSchemaResolvers,
+} from 'apollo-server-core/dist/utils/schemaInstrumentation';
 import { GraphQLDataSource } from './types';
 
 export class LocalGraphQLDataSource<TContext extends Record<string, any> = Record<string, any>> implements GraphQLDataSource<TContext> {
   constructor(public readonly schema: GraphQLSchema) {
-    // FIXME: This is needed to enable support for `resolveObject`, but we
-    // should move that to `apollo-graphql`
-    enableGraphQLExtensions(schema);
+    enablePluginsForSchemaResolvers(schema);
   }
 
   async process({

gateway-js/src/executeQueryPlan.ts

@@ -90,9 +90,7 @@ export async function executeQueryPlan<TContext>(
       },
       rootValue: data,
       variableValues: requestContext.request.variables,
-      // We have a special field resolver which ensures we support aliases.
-      // FIXME: It's _possible_ this will change after `graphql-extensions` is
-      // deprecated, though not certain. See here, also: https://git.io/Jf8cS.
+      // See also `wrapSchemaWithAliasResolver` in `gateway-js/src/index.ts`.
       fieldResolver: defaultFieldResolverWithAliasSupport,
     }));
   } catch (error) {

gateway-js/src/index.ts

@@ -494,15 +494,12 @@ export class ApolloGateway implements GraphQLService {
 
     this.logger.debug('Schema loaded and ready for execution');
 
-    // FIXME: The comment below may change when `graphql-extensions` is
-    // removed, as it will be soon.  It's not clear if this will be temporary,
-    // as is suggested, after that time, because we still very much need to
-    // do this special alias resolving.  Original comment:
-    // this is a temporary workaround for GraphQLFieldExtensions automatic
-    // wrapping of all fields when using ApolloServer. Here we wrap all fields
-    // with support for resolving aliases as part of the root value which
-    // happens because aliases are resolved by sub services and the shape
-    // of the root value already contains the aliased fields as responseNames
+    // This is a workaround for automatic wrapping of all fields, which Apollo
+    // Server does in the case of implementing resolver wrapping for plugins.
+    // Here we wrap all fields with support for resolving aliases as part of the
+    // root value which happens because aliases are resolved by sub services and
+    // the shape of the root value already contains the aliased fields as
+    // responseNames
     return { schema: wrapSchemaWithAliasResolver(schema), composedSdl };
   }
 

package.json

@@ -38,10 +38,10 @@
     "apollo-link": "1.2.14",
     "apollo-link-http": "1.5.17",
     "apollo-server": "2.17.0",
+    "apollo-server-core": "2.17.0",
     "apollo-server-env": "2.4.5",
     "apollo-server-testing": "2.17.0",
     "apollo-server-types": "0.5.1",
-    "graphql-extensions": "0.12.4",
     "bunyan": "1.8.14",
     "codecov": "3.7.2",
     "deep-freeze": "0.0.1",