bindCallback swallows error if it was thrown after the callback was executed, and the entire function is sycnhronous

[olessavluk]

RxJS version:
5.5.8

Code to reproduce:
same for node and browser

const fn = (datum, cb) => { 
  cb(datum);  
  throw new Error("callback error");
};

Rx.Observable.bindCallback(fn)(42)
  .subscribe(
    v => console.log(v), 
    e => console.error(e),
    c => console.log("completed"),
  );

Expected behavior:
see 42 and then "callback error" in the console

Actual behavior:
console output:

42
completed

Additional information:

In the real world, I've captured this issue with ReactDOM.render method. If you run it with "bad" JSX it will call passed callback first and then throw an error.

I've tried to reproduce this case as a test, but it worked well in the test environment. So maybe there is something with test scheduler or production build

    it('should error if callback throws', () => {
      const expected = new Error('haha no callback for you');
      function callback(datum, cb) {
        cb(datum);
        throw expected;
      }
      const boundCallback = Observable.bindCallback(callback, null, rxTestScheduler);

      boundCallback(42)
        .subscribe((x: number) => {
          throw 'should not next';
        }, (err: any) => {
          expect(err).to.equal(expected);
        }, () => {
          throw 'should not complete';
        });

      rxTestScheduler.flush();
    });

[benlesh]

I've updated the title of this issue, because it's specific to completely synchronous functions with callbacks.

[benlesh]

In the short term, the fix for this is to pass a scheduler to the bindCallback function: bindCallback(fn, asapScheduler) for example.

[cartant]

Closing this because it's addressed in #4089.