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

+347
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‎src/execution/__tests__/flattenAsyncIterator-test.ts

Lines changed: 145 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,145 @@
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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(
78+
(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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});
106+
expect(await doubles.next()).to.deep.equal({
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value: undefined,
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done: true,
109+
});
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});
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112+
it('allows throwing errors from a nested async generator', async () => {
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async function* source() {
114+
yield await Promise.resolve(1);
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yield await Promise.resolve(2);
116+
yield await Promise.resolve(
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(async function* nested(): AsyncGenerator<number, void, void> {
118+
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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})(),
122+
);
123+
// Not reachable, early return
124+
yield await Promise.resolve(3);
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}
126+
/* 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) {
141+
caughtError = e;
142+
}
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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
@@ -82,17 +82,22 @@ const emailSchema = new GraphQLSchema({
8282
}),
8383
});
8484

85-
function createSubscription(pubsub: SimplePubSub<Email>) {
85+
function createSubscription(
86+
pubsub: SimplePubSub<Email>,
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variableValues?: { readonly [variable: string]: unknown },
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) {
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const document = parse(`
87-
subscription ($priority: Int = 0) {
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subscription ($priority: Int = 0, $shouldDefer: Boolean = false) {
8891
importantEmail(priority: $priority) {
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email {
9093
from
9194
subject
9295
}
93-
inbox {
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unread
95-
total
96+
... @defer(if: $shouldDefer) {
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inbox {
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unread
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total
100+
}
96101
}
97102
}
98103
}
@@ -122,7 +127,12 @@ function createSubscription(pubsub: SimplePubSub<Email>) {
122127
}),
123128
};
124129

125-
return subscribe({ schema: emailSchema, document, rootValue: data });
130+
return subscribe({
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schema: emailSchema,
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document,
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rootValue: data,
134+
variableValues,
135+
});
126136
}
127137

128138
// TODO: consider adding this method to testUtils (with tests)
@@ -679,6 +689,136 @@ describe('Subscription Publish Phase', () => {
679689
});
680690
});
681691

692+
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, {
695+
shouldDefer: true,
696+
});
697+
assert(isAsyncIterable(subscription));
698+
// 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',
706+
message: 'Tests are good',
707+
unread: true,
708+
}),
709+
).to.equal(true);
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711+
// The previously waited on payload now has a value.
712+
expect(await payload).to.deep.equal({
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done: false,
714+
value: {
715+
data: {
716+
importantEmail: {
717+
email: {
718+
from: 'yuzhi@graphql.org',
719+
subject: 'Alright',
720+
},
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},
722+
},
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hasNext: true,
724+
},
725+
});
726+
727+
// Wait for the next payload from @defer
728+
expect(await subscription.next()).to.deep.equal({
729+
done: false,
730+
value: {
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data: {
732+
inbox: {
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unread: 1,
734+
total: 2,
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},
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},
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path: ['importantEmail'],
738+
hasNext: false,
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},
740+
});
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742+
// Another new email arrives, after all incrementally delivered payloads are received.
743+
expect(
744+
pubsub.emit({
745+
from: 'hyo@graphql.org',
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subject: 'Tools',
747+
message: 'I <3 making things',
748+
unread: true,
749+
}),
750+
).to.equal(true);
751+
752+
// The next waited on payload will have a value.
753+
expect(await subscription.next()).to.deep.equal({
754+
done: false,
755+
value: {
756+
data: {
757+
importantEmail: {
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email: {
759+
from: 'hyo@graphql.org',
760+
subject: 'Tools',
761+
},
762+
},
763+
},
764+
hasNext: true,
765+
},
766+
});
767+
768+
// Another new email arrives, before the incrementally delivered payloads from the last email was received.
769+
expect(
770+
pubsub.emit({
771+
from: 'adam@graphql.org',
772+
subject: 'Important',
773+
message: 'Read me please',
774+
unread: true,
775+
}),
776+
).to.equal(true);
777+
778+
// Deferred payload from previous event is received.
779+
expect(await subscription.next()).to.deep.equal({
780+
done: false,
781+
value: {
782+
data: {
783+
inbox: {
784+
unread: 2,
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total: 3,
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},
787+
},
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path: ['importantEmail'],
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hasNext: false,
790+
},
791+
});
792+
793+
// Next payload from last event
794+
expect(await subscription.next()).to.deep.equal({
795+
done: false,
796+
value: {
797+
data: {
798+
importantEmail: {
799+
email: {
800+
from: 'adam@graphql.org',
801+
subject: 'Important',
802+
},
803+
},
804+
},
805+
hasNext: true,
806+
},
807+
});
808+
809+
// The client disconnects before the deferred payload is consumed.
810+
expect(await subscription.return()).to.deep.equal({
811+
done: true,
812+
value: undefined,
813+
});
814+
815+
// Awaiting a subscription after closing it results in completed results.
816+
expect(await subscription.next()).to.deep.equal({
817+
done: true,
818+
value: undefined,
819+
});
820+
});
821+
682822
it('produces a payload when there are multiple events', async () => {
683823
const pubsub = new SimplePubSub<Email>();
684824
const subscription = createSubscription(pubsub);

‎src/execution/execute.ts

Lines changed: 6 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -52,6 +52,7 @@ import {
5252
collectFields,
5353
collectSubfields as _collectSubfields,
5454
} from './collectFields';
55+
import { flattenAsyncIterator } from './flattenAsyncIterator';
5556
import { mapAsyncIterator } from './mapAsyncIterator';
5657
import {
5758
getArgumentValues,
@@ -1397,19 +1398,11 @@ function mapSourceToResponse(
13971398
// the GraphQL specification. The `execute` function provides the
13981399
// "ExecuteSubscriptionEvent" algorithm, as it is nearly identical to the
13991400
// "ExecuteQuery" algorithm, for which `execute` is also used.
1400-
return mapAsyncIterator(resultOrStream, (payload: unknown) => {
1401-
const executionResult = executeImpl(
1402-
buildPerEventExecutionContext(exeContext, payload),
1403-
);
1404-
/* c8 ignore next 6 */
1405-
// TODO: implement support for defer/stream in subscriptions
1406-
if (isAsyncIterable(executionResult)) {
1407-
throw new Error(
1408-
'TODO: implement support for defer/stream in subscriptions',
1409-
);
1410-
}
1411-
return executionResult as PromiseOrValue<ExecutionResult>;
1412-
});
1401+
return flattenAsyncIterator<ExecutionResult, AsyncExecutionResult>(
1402+
mapAsyncIterator(resultOrStream, (payload: unknown) =>
1403+
executeImpl(buildPerEventExecutionContext(exeContext, payload)),
1404+
),
1405+
);
14131406
}
14141407

14151408
/**

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