feat(publishReplay): add higher-order lettable version of publishReplay

src/operator/publishReplay.ts

@@ -1,8 +1,7 @@
 import { Observable } from '../Observable';
-import { ReplaySubject } from '../ReplaySubject';
 import { IScheduler } from '../Scheduler';
-import { multicast } from './multicast';
 import { ConnectableObservable } from '../observable/ConnectableObservable';
+import { publishReplay as higherOrder } from '../operators';
 
 /**
  * @param bufferSize
@@ -15,5 +14,5 @@ import { ConnectableObservable } from '../observable/ConnectableObservable';
 export function publishReplay<T>(this: Observable<T>, bufferSize: number = Number.POSITIVE_INFINITY,
                                  windowTime: number = Number.POSITIVE_INFINITY,
                                  scheduler?: IScheduler): ConnectableObservable<T> {
-  return multicast.call(this, new ReplaySubject<T>(bufferSize, windowTime, scheduler));
+  return higherOrder(bufferSize, windowTime, scheduler)(this);
 }

src/operators/index.ts

@@ -55,6 +55,7 @@ export { pluck } from './pluck';
 export { publish } from './publish';
 export { publishBehavior } from './publishBehavior';
 export { publishLast } from './publishLast';
+export { publishReplay } from './publishReplay';
 export { race } from './race';
 export { reduce } from './reduce';
 export { refCount } from './refCount';

src/operators/publishReplay.ts

@@ -0,0 +1,12 @@
+import { Observable } from '../Observable';
+import { ReplaySubject } from '../ReplaySubject';
+import { IScheduler } from '../Scheduler';
+import { multicast } from './multicast';
+import { ConnectableObservable } from '../observable/ConnectableObservable';
+import { UnaryFunction } from '../interfaces';
+
+export function publishReplay<T>(bufferSize: number = Number.POSITIVE_INFINITY,
+                                 windowTime: number = Number.POSITIVE_INFINITY,
+                                 scheduler?: IScheduler): UnaryFunction<Observable<T>, ConnectableObservable<T>> {
+  return (source: Observable<T>) => multicast(new ReplaySubject<T>(bufferSize, windowTime, scheduler))(source) as ConnectableObservable<T>;
+}