compat: minimal changes to support graphql@15 within Apollo Server

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Change log
 
+### vNEXT
+
+* Filter `extensions` prior to passing them to `buildASTSchema`, in an effort to provide minimum compatibilty for `graphql@14`-compatible schemas with the upcoming `graphql@15` release. This PR does not, however, bring support for newer `graphql@15` features like interfaces implementing interfaces. [#1284](https://github.com/apollographql/graphql-tools/pull/1284)
+
 ### 4.0.6
 
 * Use `getIntrospectionQuery` instead of deprecated `introspectionQuery` constant from graphql-js

src/generate/buildSchemaFromTypeDefinitions.ts

@@ -12,6 +12,7 @@ import {
   concatenateTypeDefs,
   SchemaError,
 } from '.';
+import filterExtensionDefinitions from './filterExtensionDefinitions';
 
 function buildSchemaFromTypeDefinitions(
   typeDefinitions: ITypeDefinitions,
@@ -38,10 +39,11 @@ function buildSchemaFromTypeDefinitions(
   }
 
   const backcompatOptions = { commentDescriptions: true };
+  const typesAst = filterExtensionDefinitions(astDocument);
 
   // TODO fix types https://github.com/apollographql/graphql-tools/issues/542
   let schema: GraphQLSchema = (buildASTSchema as any)(
-    astDocument,
+    typesAst,
     backcompatOptions,
   );
 

src/generate/filterExtensionDefinitions.ts

@@ -0,0 +1,19 @@
+import { DocumentNode, DefinitionNode, Kind } from 'graphql';
+
+export default function filterExtensionDefinitions(ast: DocumentNode) {
+  const extensionDefs = ast.definitions.filter(
+    (def: DefinitionNode) =>
+      def.kind !== Kind.OBJECT_TYPE_EXTENSION &&
+      def.kind !== Kind.INTERFACE_TYPE_EXTENSION &&
+      def.kind !== Kind.INPUT_OBJECT_TYPE_EXTENSION &&
+      def.kind !== Kind.UNION_TYPE_EXTENSION &&
+      def.kind !== Kind.ENUM_TYPE_EXTENSION &&
+      def.kind !== Kind.SCALAR_TYPE_EXTENSION &&
+      def.kind !== Kind.SCHEMA_EXTENSION,
+  );
+
+  return {
+    ...ast,
+    definitions: extensionDefs,
+  };
+}

src/stitching/makeRemoteExecutableSchema.ts

@@ -31,7 +31,6 @@ import resolveParentFromTypename from './resolveFromParentTypename';
 import defaultMergedResolver from './defaultMergedResolver';
 import { checkResultAndHandleErrors } from './errors';
 import { observableToAsyncIterable } from './observableToAsyncIterable';
-import { Options as PrintSchemaOptions } from 'graphql/utilities/schemaPrinter';
 
 export type ResolverFn = (
   rootValue?: any,
@@ -49,6 +48,27 @@ export type FetcherOperation = {
   context?: { [key: string]: any };
 };
 
+/**
+ * This type has been copied inline from its source on `@types/graphql`:
+ *
+ * https://git.io/Jv8NX
+ *
+ * Previously, it was imported from `graphql/utilities/schemaPrinter`, however
+ * that module has been removed in `graphql@15`.  Furthermore, the sole property
+ * on this type is due to be deprecated in `graphql@16`.
+ */
+interface PrintSchemaOptions {
+  /**
+   * Descriptions are defined as preceding string literals, however an older
+   * experimental version of the SDL supported preceding comments as
+   * descriptions. Set to true to enable this deprecated behavior.
+   * This option is provided to ease adoption and will be removed in v16.
+   *
+   * Default: false
+   */
+  commentDescriptions?: boolean;
+}
+
 export default function makeRemoteExecutableSchema({
   schema,
   link,

src/stitching/observableToAsyncIterable.ts

@@ -2,7 +2,11 @@ import { Observable } from 'apollo-link';
 import { $$asyncIterator } from 'iterall';
 type Callback = (value?: any) => any;
 
-export function observableToAsyncIterable<T>(observable: Observable<T>): AsyncIterator<T> {
+export function observableToAsyncIterable<T>(
+  observable: Observable<T>
+): AsyncIterator<T> & {
+  [$$asyncIterator]: () => AsyncIterator<T>;
+} {
   const pullQueue: Callback[] = [];
   const pushQueue: any[] = [];