fix(throttle): properly handle default ThrottleConfig values (#7176)

* fix(throttle): properly handle default ThrottleConfig values * docs(ThrottleConfig): document "leading" and "trailing" behavior (cherry picked from commit b7a4e94)
ReactiveX · Apr 6, 2023 · ceb821c · ceb821c
1 parent 6adc66f
commit ceb821c
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Showing 4 changed files with 59 additions and 42 deletions.
diff --git a/spec/operators/throttle-spec.ts b/spec/operators/throttle-spec.ts
@@ -398,7 +398,7 @@ describe('throttle', () => {
         ];
         const expected = '-a---y----b---x---x---x---|';
 
-        const result = e1.pipe(throttle(() => e2, { leading: true, trailing: true }));
+        const result = e1.pipe(throttle(() => e2, { trailing: true }));
 
         expectObservable(result).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(e1subs);
@@ -414,7 +414,7 @@ describe('throttle', () => {
         const n1Subs = ['--^------------------!     '];
         const exp = '    --x------------------|     ';
 
-        const result = s1.pipe(throttle(() => n1, { leading: true, trailing: true }));
+        const result = s1.pipe(throttle(() => n1, { trailing: true }));
         expectObservable(result).toBe(exp);
         expectSubscriptions(s1.subscriptions).toBe(s1Subs);
         expectSubscriptions(n1.subscriptions).toBe(n1Subs);
@@ -433,7 +433,7 @@ describe('throttle', () => {
         ];
         const expected = '-a--------x---(y|)';
 
-        const result = e1.pipe(throttle(() => e2, { leading: true, trailing: true }));
+        const result = e1.pipe(throttle(() => e2, { trailing: true }));
 
         expectObservable(result).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(e1subs);

diff --git a/spec/operators/throttleTime-spec.ts b/spec/operators/throttleTime-spec.ts
@@ -20,7 +20,7 @@ describe('throttleTime operator', () => {
         const expected = '-a--------b-----c----|';
         const subs = '    ^--------------------!';
 
-        const result = e1.pipe(throttleTime(5, rxTest));
+        const result = e1.pipe(throttleTime(5));
 
         expectObservable(result).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
@@ -31,7 +31,7 @@ describe('throttleTime operator', () => {
       of(1, 2, 3)
         .pipe(throttleTime(5))
         .subscribe({
-          next: (x: number) => {
+          next: (x) => {
             expect(x).to.equal(1);
           },
           complete: done,
@@ -41,17 +41,17 @@ describe('throttleTime operator', () => {
     it('should throttle events multiple times', () => {
       const expected = ['1-0', '2-0'];
       concat(
-        timer(0, 1, rxTest).pipe(
+        timer(0, 1).pipe(
           take(3),
-          map((x: number) => '1-' + x)
+          map((x) => '1-' + x)
         ),
-        timer(8, 1, rxTest).pipe(
+        timer(8, 1).pipe(
           take(5),
-          map((x: number) => '2-' + x)
+          map((x) => '2-' + x)
         )
       )
         .pipe(throttleTime(5, rxTest))
-        .subscribe((x: string) => {
+        .subscribe((x) => {
           expect(x).to.equal(expected.shift());
         });
 
@@ -64,7 +64,7 @@ describe('throttleTime operator', () => {
         const subs = '    ^--------------------!';
         const expected = '-a--------b-----c----|';
 
-        expectObservable(e1.pipe(throttleTime(5, rxTest))).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(5))).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -75,7 +75,7 @@ describe('throttleTime operator', () => {
         const subs = '    ^------------------------!';
         const expected = 'a-----a-----a-----a-----a|';
 
-        expectObservable(e1.pipe(throttleTime(5, rxTest))).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(5))).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -86,7 +86,7 @@ describe('throttleTime operator', () => {
         const subs = '    ^----!';
         const expected = '-----|';
 
-        expectObservable(e1.pipe(throttleTime(5, rxTest))).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(5))).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -97,7 +97,7 @@ describe('throttleTime operator', () => {
         const subs = '    ^----!';
         const expected = '-----#';
 
-        expectObservable(e1.pipe(throttleTime(10, rxTest))).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(10))).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -108,7 +108,7 @@ describe('throttleTime operator', () => {
         const subs = '    (^!)';
         const expected = '|';
 
-        expectObservable(e1.pipe(throttleTime(30, rxTest))).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(30))).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -119,7 +119,7 @@ describe('throttleTime operator', () => {
         const subs = '    ^';
         const expected = '-';
 
-        expectObservable(e1.pipe(throttleTime(30, rxTest))).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(30))).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -130,7 +130,7 @@ describe('throttleTime operator', () => {
         const subs = '    (^!)';
         const expected = '#';
 
-        expectObservable(e1.pipe(throttleTime(30, rxTest))).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(30))).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -142,7 +142,7 @@ describe('throttleTime operator', () => {
         const subs = '    ^------------------------------!';
         const expected = '-a-------------d----------------';
 
-        expectObservable(e1.pipe(throttleTime(5, rxTest)), unsub).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(5)), unsub).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -155,9 +155,9 @@ describe('throttleTime operator', () => {
         const unsub = '   -------------------------------!';
 
         const result = e1.pipe(
-          mergeMap((x: string) => of(x)),
-          throttleTime(5, rxTest),
-          mergeMap((x: string) => of(x))
+          mergeMap((x) => of(x)),
+          throttleTime(5),
+          mergeMap((x) => of(x))
         );
 
         expectObservable(result, unsub).toBe(expected);
@@ -171,7 +171,7 @@ describe('throttleTime operator', () => {
         const subs = '    ^------------------------------!';
         const expected = '-a-------------d---------------#';
 
-        expectObservable(e1.pipe(throttleTime(5, rxTest))).toBe(expected);
+        expectObservable(e1.pipe(throttleTime(5))).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(subs);
       });
     });
@@ -186,7 +186,7 @@ describe('throttleTime operator', () => {
         //                     ----|----|---|---|
         const expected = '-a---y----b---x---x---(x|)';
 
-        const result = e1.pipe(throttleTime(t, rxTest, { leading: true, trailing: true }));
+        const result = e1.pipe(throttleTime(t, rxTest, { trailing: true }));
 
         expectObservable(result).toBe(expected);
         expectSubscriptions(e1.subscriptions).toBe(e1subs);
@@ -199,7 +199,7 @@ describe('throttleTime operator', () => {
         const t = time('   ----|                 ');
         const expected = '-a--------------------|';
 
-        const result = e1.pipe(throttleTime(t, rxTest, { leading: true, trailing: true }));
+        const result = e1.pipe(throttleTime(t, rxTest, { trailing: true }));
 
         expectObservable(result).toBe(expected);
       });

diff --git a/src/internal/operators/throttle.ts b/src/internal/operators/throttle.ts
@@ -5,16 +5,36 @@ import { operate } from '../util/lift';
 import { createOperatorSubscriber } from './OperatorSubscriber';
 import { innerFrom } from '../observable/innerFrom';
 
+/**
+ * An object interface used by {@link throttle} or {@link throttleTime} that ensure
+ * configuration options of these operators.
+ *
+ * @see {@link throttle}
+ * @see {@link throttleTime}
+ */
 export interface ThrottleConfig {
+  /**
+   * If `true`, the resulting Observable will emit the first value from the source
+   * Observable at the **start** of the "throttling" process (when starting an
+   * internal timer that prevents other emissions from the source to pass through).
+   * If `false`, it will not emit the first value from the source Observable at the
+   * start of the "throttling" process.
+   *
+   * If not provided, defaults to: `true`.
+   */
   leading?: boolean;
+  /**
+   * If `true`, the resulting Observable will emit the last value from the source
+   * Observable at the **end** of the "throttling" process (when ending an internal
+   * timer that prevents other emissions from the source to pass through).
+   * If `false`, it will not emit the last value from the source Observable at the
+   * end of the "throttling" process.
+   *
+   * If not provided, defaults to: `false`.
+   */
   trailing?: boolean;
 }
 
-export const defaultThrottleConfig: ThrottleConfig = {
-  leading: true,
-  trailing: false,
-};
-
 /**
  * Emits a value from the source Observable, then ignores subsequent source
  * values for a duration determined by another Observable, then repeats this
@@ -53,20 +73,17 @@ export const defaultThrottleConfig: ThrottleConfig = {
  * @see {@link sample}
  * @see {@link throttleTime}
  *
- * @param durationSelector A function
- * that receives a value from the source Observable, for computing the silencing
- * duration for each source value, returned as an Observable or a Promise.
- * @param config a configuration object to define `leading` and `trailing` behavior. Defaults
- * to `{ leading: true, trailing: false }`.
+ * @param durationSelector A function that receives a value from the source
+ * Observable, for computing the silencing duration for each source value,
+ * returned as an `ObservableInput`.
+ * @param config A configuration object to define `leading` and `trailing`
+ * behavior. Defaults to `{ leading: true, trailing: false }`.
  * @return A function that returns an Observable that performs the throttle
  * operation to limit the rate of emissions from the source.
  */
-export function throttle<T>(
-  durationSelector: (value: T) => ObservableInput<any>,
-  config: ThrottleConfig = defaultThrottleConfig
-): MonoTypeOperatorFunction<T> {
+export function throttle<T>(durationSelector: (value: T) => ObservableInput<any>, config?: ThrottleConfig): MonoTypeOperatorFunction<T> {
   return operate((source, subscriber) => {
-    const { leading, trailing } = config;
+    const { leading = true, trailing = false } = config ?? {};
     let hasValue = false;
     let sendValue: T | null = null;
     let throttled: Subscription | null = null;

diff --git a/src/internal/operators/throttleTime.ts b/src/internal/operators/throttleTime.ts
@@ -1,5 +1,5 @@
 import { asyncScheduler } from '../scheduler/async';
-import { defaultThrottleConfig, throttle } from './throttle';
+import { throttle, ThrottleConfig } from './throttle';
 import { MonoTypeOperatorFunction, SchedulerLike } from '../types';
 import { timer } from '../observable/timer';
 
@@ -47,15 +47,15 @@ import { timer } from '../observable/timer';
  * internally by the optional `scheduler`.
  * @param scheduler The {@link SchedulerLike} to use for
  * managing the timers that handle the throttling. Defaults to {@link asyncScheduler}.
- * @param config a configuration object to define `leading` and
+ * @param config A configuration object to define `leading` and
  * `trailing` behavior. Defaults to `{ leading: true, trailing: false }`.
  * @return A function that returns an Observable that performs the throttle
  * operation to limit the rate of emissions from the source.
  */
 export function throttleTime<T>(
   duration: number,
   scheduler: SchedulerLike = asyncScheduler,
-  config = defaultThrottleConfig
+  config?: ThrottleConfig
 ): MonoTypeOperatorFunction<T> {
   const duration$ = timer(duration, scheduler);
   return throttle(() => duration$, config);