[refactored] rewriteTo to have shorthand signature

Summary: Part of #230 Reviewers: O2 Material Motion, O3 Material JavaScript platform reviewers, #material_motion, vietanh Reviewed By: #material_motion, vietanh Tags: #material_motion Differential Revision: http://codereview.cc/D3429
material-motion · Oct 11, 2017 · 9102418 · 9102418
1 parent 6aaa6cd
commit 9102418
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Showing 3 changed files with 46 additions and 5 deletions.
diff --git a/packages/core/src/interactions/Swipeable.ts b/packages/core/src/interactions/Swipeable.ts
@@ -184,15 +184,13 @@ export class Swipeable {
     subscribe({
       sink: spring.enabled$,
       source: this.whenThresholdFirstCrossed$.merge([
-        when(spring.state$.isAnyOf([ State.AT_REST ])).rewriteTo({
-          value$: false,
-        })
+        when(spring.state$.isAnyOf([ State.AT_REST ])).rewriteTo(false),
       ]),
     });
 
     subscribe({
       sink: tossable.resistanceFactor$,
-      source: this.whenThresholdCrossed$.rewriteTo({ value$: DISABLED_RESISTANCE_FACTOR }),
+      source: this.whenThresholdCrossed$.rewriteTo(DISABLED_RESISTANCE_FACTOR),
     });
 
     subscribe({

diff --git a/packages/core/src/operators/__tests__/rewriteTo.test.ts b/packages/core/src/operators/__tests__/rewriteTo.test.ts
@@ -95,5 +95,36 @@ describe('motionObservable.rewriteTo',
         expect(listener).to.have.been.calledTwice.and.to.have.been.calledWith(12).and.to.have.been.calledWith(15);
       }
     );
+
+    it('should have a shorthand signature for constants',
+      () => {
+        stream.rewriteTo('banana').subscribe(listener);
+
+        mockObserver.next();
+        mockObserver.next(false);
+        mockObserver.next(123);
+        mockObserver.next({a: '1234'});
+
+        expect(listener).to.have.callCount(4).and.to.always.have.been.calledWith('banana');
+      }
+    );
+
+    it('should have a shorthand signature for streams',
+      () => {
+        stream.rewriteTo(value$).subscribe(listener);
+
+        mockObserver.next();
+        mockObserver.next(false);
+
+        value$.next(12);
+        value$.next(15);
+
+        expect(listener).to.have.been.calledOnce.and.to.have.been.calledWith(12);
+
+        mockObserver.next({});
+
+        expect(listener).to.have.been.calledTwice.and.to.have.been.calledWith(15);
+      }
+    );
   }
 );
diff --git a/packages/core/src/operators/rewriteTo.ts b/packages/core/src/operators/rewriteTo.ts
@@ -22,24 +22,36 @@ import {
   ObservableWithMotionOperators,
 } from '../types';
 
+import {
+  isDefined,
+} from '../typeGuards';
+
 import {
   _ReactiveMapOptions,
 } from './foundation/_reactiveMap';
 
+export type RewriteToValue<U> = U | Observable<U>;
 export type RewriteToArgs<U> = _ReactiveMapOptions & {
-  value$: U | Observable<U>,
+  value$: RewriteToValue<U>,
 };
 
 export interface MotionRewriteToable {
   rewriteTo<U>(kwargs: RewriteToArgs<U>): ObservableWithMotionOperators<U>;
+  rewriteTo<U>(value$: RewriteToValue<U>): ObservableWithMotionOperators<U>;
 }
 
 export function withRewriteTo<T, S extends Constructor<MotionReactiveMappable<T>>>(superclass: S): S & Constructor<MotionRewriteToable> {
   return class extends superclass implements MotionRewriteToable {
     /**
      * Dispatches its argument every time it receives a value from upstream.
      */
+    rewriteTo<U>(value$: RewriteToValue<U>): ObservableWithMotionOperators<U>;
+    rewriteTo<U>(kwargs: RewriteToArgs<U>): ObservableWithMotionOperators<U>;
     rewriteTo<U>({ value$, onlyDispatchWithUpstream = true, ...reactiveMapOptions }: RewriteToArgs<U>): ObservableWithMotionOperators<U> {
+      if (!isDefined(value$)) {
+        value$ = arguments[0];
+      }
+
       return this._reactiveMap({
         transform: ({ value }) => value,
         inputs: {