SafeSubscriber does not unsubscribe itself

When subscribing to Observable with Partial Observer, rxjs creates SafeSubscriber, but on unsubscribe it does not unsubscribe itself. Moreover if a closure is passed to next/error callback of partial observer, this leads to memory leaks, as consumers cannot be freed.

See the code (pure JS).

RxJS version: 5.4.1

Code to reproduce:

via gist: https://gist.github.com/czterocyty/d4ad5dea55316c9a734c64f378975f04

Expected behavior:

I think SafeSubscriber#unsubscribe should be called too upon unsubscription.

Test should pass:

  it('upon subscription, the destination SafeSubscriber should be unsubscribed too', () => {
    const observer = {
      next: function () { /*noop*/ },
      error: function (e) { throw e; }
    };

    const sub = new Subscriber(observer);

    const destination = sub['destination'];
    const destUnsubscribe = destination['unsubscribe'] = sinon.spy();
    const destUnsubscribeProtected = destination['_unsubscribe'] = sinon.spy();

    sub.unsubscribe();

    expect(sub.closed).to.eq(true);
    expect(destination.closed).to.eq(true);

    expect(destUnsubscribe).have.been.called;
    expect(destUnsubscribeProtected).have.been.called;
  });

Actual behavior:

It is not when passing partial observer into Subscriber.

Additional information:

After playing around with buttons, check JS heap and not-freed Foo instance due to handing closures in SafeSubscriber. See https://drive.google.com/open?id=0B4JH51FD7JBZcUJTTVRjRXJ2a00. There is Subscriber which is closed (good), but destination as SafeSubscriber is still not closed.

[trxcllnt]

Here ya go everybody https://github.com/ReactiveX/rxjs/pull/5311

[cartant]

(For my own reference) this issue is somewhat related to this one: https://github.com/ReactiveX/rxjs/pull/5243