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add defer/stream support for subscriptions (#7)
# Conflicts: # src/subscription/subscribe.ts
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4 files changed

+352
-20
lines changed

4 files changed

+352
-20
lines changed

‎src/execution/__tests__/flattenAsyncIterator-test.ts

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import { expect } from 'chai';
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import { describe, it } from 'mocha';
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import { flattenAsyncIterator } from '../flattenAsyncIterator';
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describe('flattenAsyncIterator', () => {
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it('does not modify an already flat async generator', async () => {
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async function* source() {
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yield await Promise.resolve(1);
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yield await Promise.resolve(2);
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yield await Promise.resolve(3);
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}
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const result = flattenAsyncIterator(source());
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expect(await result.next()).to.deep.equal({ value: 1, done: false });
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expect(await result.next()).to.deep.equal({ value: 2, done: false });
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expect(await result.next()).to.deep.equal({ value: 3, done: false });
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expect(await result.next()).to.deep.equal({
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value: undefined,
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done: true,
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});
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});
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it('does not modify an already flat async iterator', async () => {
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const items = [1, 2, 3];
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const iterator: any = {
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[Symbol.asyncIterator]() {
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return this;
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},
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next() {
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return Promise.resolve({
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done: items.length === 0,
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value: items.shift(),
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});
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},
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};
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const result = flattenAsyncIterator(iterator);
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expect(await result.next()).to.deep.equal({ value: 1, done: false });
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expect(await result.next()).to.deep.equal({ value: 2, done: false });
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expect(await result.next()).to.deep.equal({ value: 3, done: false });
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expect(await result.next()).to.deep.equal({
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value: undefined,
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done: true,
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});
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});
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it('flatten nested async generators', async () => {
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async function* source() {
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yield await Promise.resolve(1);
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yield await Promise.resolve(2);
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yield await Promise.resolve(
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(async function* nested(): AsyncGenerator<number, void, void> {
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yield await Promise.resolve(2.1);
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yield await Promise.resolve(2.2);
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})(),
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);
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yield await Promise.resolve(3);
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}
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const doubles = flattenAsyncIterator(source());
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const result = [];
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for await (const x of doubles) {
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result.push(x);
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}
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expect(result).to.deep.equal([1, 2, 2.1, 2.2, 3]);
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});
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it('allows returning early from a nested async generator', async () => {
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async function* source() {
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yield await Promise.resolve(1);
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yield await Promise.resolve(2);
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yield await Promise.resolve(
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(async function* nested(): AsyncGenerator<number, void, void> {
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yield await Promise.resolve(2.1); /* c8 ignore start */
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// Not reachable, early return
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yield await Promise.resolve(2.2);
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})(),
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);
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// Not reachable, early return
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yield await Promise.resolve(3);
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}
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/* c8 ignore stop */
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const doubles = flattenAsyncIterator(source());
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expect(await doubles.next()).to.deep.equal({ value: 1, done: false });
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expect(await doubles.next()).to.deep.equal({ value: 2, done: false });
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expect(await doubles.next()).to.deep.equal({ value: 2.1, done: false });
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// Early return
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expect(await doubles.return()).to.deep.equal({
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value: undefined,
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done: true,
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});
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// Subsequent next calls
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expect(await doubles.next()).to.deep.equal({
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value: undefined,
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done: true,
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});
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expect(await doubles.next()).to.deep.equal({
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value: undefined,
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done: true,
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});
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});
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it('allows throwing errors from a nested async generator', async () => {
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async function* source() {
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yield await Promise.resolve(1);
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yield await Promise.resolve(2);
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yield await Promise.resolve(
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(async function* nested(): AsyncGenerator<number, void, void> {
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yield await Promise.resolve(2.1); /* c8 ignore start */
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// Not reachable, early return
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yield await Promise.resolve(2.2);
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})(),
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);
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// Not reachable, early return
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yield await Promise.resolve(3);
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}
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/* c8 ignore stop */
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const doubles = flattenAsyncIterator(source());
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expect(await doubles.next()).to.deep.equal({ value: 1, done: false });
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expect(await doubles.next()).to.deep.equal({ value: 2, done: false });
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expect(await doubles.next()).to.deep.equal({ value: 2.1, done: false });
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// Throw error
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let caughtError;
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try {
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await doubles.throw('ouch'); /* c8 ignore start */
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// Not reachable, always throws
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/* c8 ignore stop */
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} catch (e) {
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caughtError = e;
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}
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expect(caughtError).to.equal('ouch');
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});
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});

‎src/execution/__tests__/subscribe-test.ts

Lines changed: 146 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -80,17 +80,22 @@ const emailSchema = new GraphQLSchema({
8080
}),
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});
8282

83-
function createSubscription(pubsub: SimplePubSub<Email>) {
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function createSubscription(
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pubsub: SimplePubSub<Email>,
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variableValues?: { readonly [variable: string]: unknown },
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) {
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const document = parse(`
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subscription ($priority: Int = 0) {
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subscription ($priority: Int = 0, $shouldDefer: Boolean = false) {
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importantEmail(priority: $priority) {
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email {
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from
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subject
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}
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inbox {
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unread
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total
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... @defer(if: $shouldDefer) {
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inbox {
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unread
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total
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}
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}
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}
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}
@@ -120,7 +125,12 @@ function createSubscription(pubsub: SimplePubSub<Email>) {
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}),
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};
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123-
return subscribe({ schema: emailSchema, document, rootValue: data });
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return subscribe({
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schema: emailSchema,
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document,
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rootValue: data,
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variableValues,
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});
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}
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126136
async function expectPromise(promise: Promise<unknown>) {
@@ -675,6 +685,136 @@ describe('Subscription Publish Phase', () => {
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});
676686
});
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it('produces additional payloads for subscriptions with @defer', async () => {
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const pubsub = new SimplePubSub<Email>();
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const subscription = await createSubscription(pubsub, {
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shouldDefer: true,
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});
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invariant(isAsyncIterable(subscription));
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// Wait for the next subscription payload.
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const payload = subscription.next();
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// A new email arrives!
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expect(
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pubsub.emit({
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from: 'yuzhi@graphql.org',
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subject: 'Alright',
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message: 'Tests are good',
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unread: true,
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}),
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).to.equal(true);
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// The previously waited on payload now has a value.
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expect(await payload).to.deep.equal({
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done: false,
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value: {
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data: {
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importantEmail: {
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email: {
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from: 'yuzhi@graphql.org',
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subject: 'Alright',
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},
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},
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},
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hasNext: true,
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},
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});
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// Wait for the next payload from @defer
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expect(await subscription.next()).to.deep.equal({
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done: false,
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value: {
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data: {
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inbox: {
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unread: 1,
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total: 2,
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},
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},
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path: ['importantEmail'],
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hasNext: false,
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},
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});
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// Another new email arrives, after all incrementally delivered payloads are received.
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expect(
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pubsub.emit({
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from: 'hyo@graphql.org',
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subject: 'Tools',
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message: 'I <3 making things',
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unread: true,
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}),
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).to.equal(true);
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// The next waited on payload will have a value.
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expect(await subscription.next()).to.deep.equal({
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done: false,
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value: {
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data: {
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importantEmail: {
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email: {
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from: 'hyo@graphql.org',
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subject: 'Tools',
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},
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},
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},
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hasNext: true,
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},
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});
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// Another new email arrives, before the incrementally delivered payloads from the last email was received.
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expect(
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pubsub.emit({
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from: 'adam@graphql.org',
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subject: 'Important',
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message: 'Read me please',
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unread: true,
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}),
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).to.equal(true);
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// Deferred payload from previous event is received.
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expect(await subscription.next()).to.deep.equal({
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done: false,
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value: {
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data: {
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inbox: {
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unread: 2,
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total: 3,
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},
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},
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path: ['importantEmail'],
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hasNext: false,
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},
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});
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// Next payload from last event
790+
expect(await subscription.next()).to.deep.equal({
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done: false,
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value: {
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data: {
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importantEmail: {
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email: {
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from: 'adam@graphql.org',
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subject: 'Important',
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},
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},
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},
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hasNext: true,
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},
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});
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// The client disconnects before the deferred payload is consumed.
806+
expect(await subscription.return()).to.deep.equal({
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done: true,
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value: undefined,
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});
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811+
// Awaiting a subscription after closing it results in completed results.
812+
expect(await subscription.next()).to.deep.equal({
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done: true,
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value: undefined,
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});
816+
});
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678818
it('produces a payload when there are multiple events', async () => {
679819
const pubsub = new SimplePubSub<Email>();
680820
const subscription = await createSubscription(pubsub);

‎src/execution/flattenAsyncIterator.ts

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import { isAsyncIterable } from '../jsutils/isAsyncIterable';
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type AsyncIterableOrGenerator<T> =
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| AsyncGenerator<T, void, void>
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| AsyncIterable<T>;
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/**
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* Given an AsyncIterable that could potentially yield other async iterators,
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* flatten all yielded results into a single AsyncIterable
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*/
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export function flattenAsyncIterator<T, AT>(
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iterable: AsyncIterableOrGenerator<T | AsyncIterableOrGenerator<AT>>,
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): AsyncGenerator<T | AT, void, void> {
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const iteratorMethod = iterable[Symbol.asyncIterator];
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const iterator: any = iteratorMethod.call(iterable);
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let iteratorStack: Array<AsyncIterator<T>> = [iterator];
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async function next(): Promise<IteratorResult<T | AT, void>> {
19+
const currentIterator = iteratorStack[0];
20+
if (!currentIterator) {
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return { value: undefined, done: true };
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}
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const result = await currentIterator.next();
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if (result.done) {
25+
iteratorStack.shift();
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return next();
27+
} else if (isAsyncIterable(result.value)) {
28+
const childIterator = result.value[
29+
Symbol.asyncIterator
30+
]() as AsyncIterator<T>;
31+
iteratorStack.unshift(childIterator);
32+
return next();
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}
34+
return result;
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}
36+
return {
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next,
38+
return() {
39+
iteratorStack = [];
40+
return iterator.return();
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},
42+
throw(error?: unknown): Promise<IteratorResult<T | AT>> {
43+
iteratorStack = [];
44+
return iterator.throw(error);
45+
},
46+
[Symbol.asyncIterator]() {
47+
return this;
48+
},
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};
50+
}

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