TS: Fix strict issues in src/subscription

src/subscription/__tests__/mapAsyncIterator-test.ts

@@ -33,7 +33,9 @@ describe('mapAsyncIterator', () => {
 
       next(): Promise<IteratorResult<number, void>> {
         if (items.length > 0) {
-          return Promise.resolve({ done: false, value: items.shift() });
+          const value = items[0];
+          items.shift();
+          return Promise.resolve({ done: false, value });
         }
 
         return Promise.resolve({ done: true, value: undefined });
@@ -105,8 +107,7 @@ describe('mapAsyncIterator', () => {
     expect(await doubles.next()).to.deep.equal({ value: 4, done: false });
 
     // Early return
-    // @ts-expect-error FIXME: TS Conversion
-    expect(await doubles.return()).to.deep.equal({
+    expect(await doubles.return('')).to.deep.equal({
       value: 'The End',
       done: true,
     });
@@ -130,9 +131,11 @@ describe('mapAsyncIterator', () => {
         return this;
       },
       next() {
+        const value = items[0];
+        items.shift();
         return Promise.resolve({
           done: items.length === 0,
-          value: items.shift(),
+          value,
         });
       },
     };
@@ -143,8 +146,7 @@ describe('mapAsyncIterator', () => {
     expect(await doubles.next()).to.deep.equal({ value: 4, done: false });
 
     // Early return
-    // @ts-expect-error FIXME: TS Conversion
-    expect(await doubles.return()).to.deep.equal({
+    expect(await doubles.return(0)).to.deep.equal({
       value: undefined,
       done: true,
     });
@@ -194,9 +196,11 @@ describe('mapAsyncIterator', () => {
         return this;
       },
       next() {
+        const value = items[0];
+        items.shift();
         return Promise.resolve({
           done: items.length === 0,
-          value: items.shift(),
+          value,
         });
       },
     };

src/subscription/__tests__/simplePubSub.ts

@@ -1,3 +1,5 @@
+import { invariant } from '../../jsutils/invariant';
+
 /**
  * Create an AsyncIterator from an EventEmitter. Useful for mocking a
  * PubSub system for tests.
@@ -18,7 +20,7 @@ export class SimplePubSub<T> {
 
   getSubscriber<R>(transform: (value: T) => R): AsyncGenerator<R, void, void> {
     const pullQueue: Array<(result: IteratorResult<R, void>) => void> = [];
-    const pushQueue = [];
+    const pushQueue: Array<R> = [];
     let listening = true;
     this._subscribers.add(pushValue);
 
@@ -33,13 +35,15 @@ export class SimplePubSub<T> {
     };
 
     return {
-      next() {
+      next(): Promise<IteratorResult<R, void>> {
         if (!listening) {
           return Promise.resolve({ value: undefined, done: true });
         }
 
         if (pushQueue.length > 0) {
-          return Promise.resolve({ value: pushQueue.shift(), done: false });
+          const value = pushQueue[0];
+          pushQueue.shift();
+          return Promise.resolve({ value, done: false });
         }
         return new Promise((resolve) => pullQueue.push(resolve));
       },
@@ -59,7 +63,9 @@ export class SimplePubSub<T> {
     function pushValue(event: T): void {
       const value: R = transform(event);
       if (pullQueue.length > 0) {
-        pullQueue.shift()({ value, done: false });
+        const receiver = pullQueue.shift();
+        invariant(receiver);
+        receiver({ value, done: false });
       } else {
         pushQueue.push(value);
       }

src/subscription/__tests__/subscribe-test.ts

@@ -42,7 +42,8 @@ const InboxType = new GraphQLObjectType({
     },
     unread: {
       type: GraphQLInt,
-      resolve: (inbox) => inbox.emails.filter((email) => email.unread).length,
+      resolve: (inbox) =>
+        inbox.emails.filter((email: any) => email.unread).length,
     },
     emails: { type: new GraphQLList(EmailType) },
   },
@@ -103,7 +104,7 @@ function createSubscription(pubsub: SimplePubSub<Email>) {
     },
   ];
 
-  const data = {
+  const data: any = {
     inbox: { emails },
     // FIXME: we shouldn't use mapAsyncIterator here since it makes tests way more complex
     importantEmail: pubsub.getSubscriber((newEmail) => {
@@ -122,7 +123,7 @@ function createSubscription(pubsub: SimplePubSub<Email>) {
 }
 
 async function expectPromise(promise: Promise<unknown>) {
-  let caughtError;
+  let caughtError: Error;
 
   try {
     await promise;
@@ -136,7 +137,7 @@ async function expectPromise(promise: Promise<unknown>) {
     toReject() {
       expect(caughtError).to.be.an.instanceOf(Error);
     },
-    toRejectWith(message) {
+    toRejectWith(message: string) {
       expect(caughtError).to.be.an.instanceOf(Error);
       expect(caughtError).to.have.property('message', message);
     },
@@ -312,6 +313,7 @@ describe('Subscription Initialization Phase', () => {
       }),
     });
 
+    // TODO ts-expect-error (schema must not be null)
     (await expectPromise(subscribe({ schema: null, document }))).toRejectWith(
       'Expected null to be a GraphQL schema.',
     );
@@ -321,6 +323,7 @@ describe('Subscription Initialization Phase', () => {
       'Expected undefined to be a GraphQL schema.',
     );
 
+    // TODO ts-expect-error (document must not be null)
     (await expectPromise(subscribe({ schema, document: null }))).toRejectWith(
       'Must provide document.',
     );

src/subscription/mapAsyncIterator.ts

@@ -8,7 +8,6 @@ export function mapAsyncIterator<T, U, R = undefined>(
   iterable: AsyncGenerator<T, R, void> | AsyncIterable<T>,
   callback: (value: T) => PromiseOrValue<U>,
 ): AsyncGenerator<U, R, void> {
-  // $FlowIssue[incompatible-use]
   const iterator = iterable[Symbol.asyncIterator]();
 
   async function mapResult(
@@ -39,9 +38,10 @@ export function mapAsyncIterator<T, U, R = undefined>(
       return mapResult(await iterator.next());
     },
     async return(): Promise<IteratorResult<U, R>> {
+      // If iterator.return() does not exist, then type R must be undefined.
       return typeof iterator.return === 'function'
         ? mapResult(await iterator.return())
-        : { value: undefined, done: true };
+        : { value: undefined as any, done: true };
     },
     async throw(error?: unknown) {
       return typeof iterator.throw === 'function'

src/subscription/subscribe.ts

@@ -92,7 +92,7 @@ export async function subscribe(
   // the GraphQL specification. The `execute` function provides the
   // "ExecuteSubscriptionEvent" algorithm, as it is nearly identical to the
   // "ExecuteQuery" algorithm, for which `execute` is also used.
-  const mapSourceToResponse = (payload) =>
+  const mapSourceToResponse = (payload: unknown) =>
     execute({
       schema,
       document,
@@ -161,11 +161,10 @@ export async function createSourceEventStream(
     );
 
     // Return early errors if execution context failed.
-    if (Array.isArray(exeContext)) {
+    if (!('schema' in exeContext)) {
       return { errors: exeContext };
     }
 
-    // @ts-expect-error FIXME: TS Conversion
     const eventStream = await executeSubscription(exeContext);
 
     // Assert field returned an event stream, otherwise yield an error.