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fix(throttleTime): emit single value with trailing enabled (#4564)
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* test(throttleTime): test single value with trailing enabled

Test if throttleTime emits when only a single value is emitted from the
source with leading enabled/disabled and trailing enabled.

* fix(throttleTime): fix single value with leading disabled, trailing enabled

Emit single value with leading disabled, trailing enabled.

Closes #2859 and #4491.

* chore: improve test descriptions

And remove an asDiagram call made with the same argument.

Signed-off-by: Matthias Kunnen <matthias.kunnen@gmail.com>
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MatthiasKunnen authored and benlesh committed Apr 23, 2019
1 parent e460eec commit fd690a6
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Showing 2 changed files with 29 additions and 6 deletions.
32 changes: 26 additions & 6 deletions spec/operators/throttleTime-spec.ts
Original file line number Diff line number Diff line change
Expand Up @@ -141,24 +141,34 @@ describe('throttleTime operator', () => {
});

describe('throttleTime(fn, { leading: true, trailing: true })', () => {
asDiagram('throttleTime(fn, { leading: true, trailing: true })')('should immediately emit the first value in each time window', () => {
asDiagram('throttleTime(fn, { leading: true, trailing: true })')('should immediately emit the first and last values in each time window', () => {
const e1 = hot('-a-xy-----b--x--cxxx--|');
const e1subs = '^ !';
const t = time( '----| ');
const t = time( '----| ');
const expected = '-a---y----b---x-c---x-|';

const result = e1.pipe(throttleTime(t, rxTestScheduler, { leading: true, trailing: true }));

expectObservable(result).toBe(expected);
expectSubscriptions(e1.subscriptions).toBe(e1subs);
});

it('should emit the value if only a single one is given', () => {
const e1 = hot('-a--------------------|');
const t = time('----| ');
const expected = '-a--------------------|';

const result = e1.pipe(throttleTime(t, rxTestScheduler, { leading: true, trailing: true }));

expectObservable(result).toBe(expected);
});
});

describe('throttleTime(fn, { leading: false, trailing: true })', () => {
asDiagram('throttleTime(fn, { leading: false, trailing: true })')('should immediately emit the first value in each time window', () => {
asDiagram('throttleTime(fn, { leading: false, trailing: true })')('should immediately emit the last value in each time window', () => {
const e1 = hot('-a-xy-----b--x--cxxx--|');
const e1subs = '^ !';
const t = time( '----| ');
const t = time( '----| ');
const expected = '-----y--------x-----x-|';

const result = e1.pipe(throttleTime(t, rxTestScheduler, { leading: false, trailing: true }));
Expand All @@ -167,16 +177,26 @@ describe('throttleTime operator', () => {
expectSubscriptions(e1.subscriptions).toBe(e1subs);
});

asDiagram('throttleTime(fn, { leading: false, trailing: true })')('should emit the last throttled value when complete', () => {
it('should emit the last throttled value when complete', () => {
const e1 = hot('-a-xy-----b--x--cxx|');
const e1subs = '^ !';
const t = time('----| ');
const t = time('----| ');
const expected = '-----y--------x----(x|)';

const result = e1.pipe(throttleTime(t, rxTestScheduler, { leading: false, trailing: true }));

expectObservable(result).toBe(expected);
expectSubscriptions(e1.subscriptions).toBe(e1subs);
});

it('should emit the value if only a single one is given', () => {
const e1 = hot('-a--------------------|');
const t = time('----| ');
const expected = '-----a----------------|';

const result = e1.pipe(throttleTime(t, rxTestScheduler, { leading: false, trailing: true }));

expectObservable(result).toBe(expected);
});
});
});
3 changes: 3 additions & 0 deletions src/internal/operators/throttleTime.ts
Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,9 @@ class ThrottleTimeSubscriber<T> extends Subscriber<T> {
this.add(this.throttled = this.scheduler.schedule<DispatchArg<T>>(dispatchNext, this.duration, { subscriber: this }));
if (this.leading) {
this.destination.next(value);
} else if (this.trailing) {
this._trailingValue = value;
this._hasTrailingValue = true;
}
}
}
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