fix(bindNodeCallback): emit undefined when callback has no success ar…

…guments

Emit undefined insteady of empty array by resulting Observable,
when callback function is called without success parameters.

Closes ReactiveX#2254

spec/observables/bindNodeCallback-spec.ts

@@ -8,6 +8,24 @@ const Observable = Rx.Observable;
 /** @test {bindNodeCallback} */
 describe('Observable.bindNodeCallback', () => {
  describe('when not scheduled', () => {
+ it('should emit undefined when callback is called without success arguments', () => {
+ function callback(cb) {
+ cb(null);
+ }
+
+ const boundCallback = Observable.bindNodeCallback(callback);
+ const results = [];
+
+ boundCallback()
+ .subscribe((x: any) => {
+ results.push(typeof x);
+ }, null, () => {
+ results.push('done');
+ });
+
+ expect(results).to.deep.equal(['undefined', 'done']);
+ });
+
  it('should emit one value from a callback', () => {
  function callback(datum, cb) {
  cb(null, datum);
@@ -126,6 +144,26 @@ describe('Observable.bindNodeCallback', () => {
  });
 
  describe('when scheduled', () => {
+ it('should emit undefined when callback is called without success arguments', () => {
+ function callback(cb) {
+ cb(null);
+ }
+
+ const boundCallback = Observable.bindNodeCallback(callback, null, rxTestScheduler);
+ const results = [];
+
+ boundCallback()
+ .subscribe((x: any) => {
+ results.push(typeof x);
+ }, null, () => {
+ results.push('done');
+ });
+
+ rxTestScheduler.flush();
+
+ expect(results).to.deep.equal(['undefined', 'done']);
+ });
+
  it('should emit one value from a callback', () => {
  function callback(datum, cb) {
  cb(null, datum);

src/observable/BoundNodeCallbackObservable.ts

@@ -112,7 +112,7 @@ export class BoundNodeCallbackObservable<T> extends Observable<T> {
  subject.complete();
  }
  } else {
- subject.next(innerArgs.length === 1 ? innerArgs[0] : innerArgs);
+ subject.next(innerArgs.length <= 1 ? innerArgs[0] : innerArgs);
  subject.complete();
  }
  };
@@ -162,7 +162,7 @@ function dispatch<T>(this: Action<DispatchState<T>>, state: DispatchState<T>) {
  self.add(scheduler.schedule(dispatchNext, 0, { value: result, subject }));
  }
  } else {
- const value = innerArgs.length === 1 ? innerArgs[0] : innerArgs;
+ const value = innerArgs.length <= 1 ? innerArgs[0] : innerArgs;
  self.add(scheduler.schedule(dispatchNext, 0, { value, subject }));
  }
  };