OnErrorNotImplementedException disrupts Subject event delivery

[vadims]

No description provided.

[vadims]

The following example hangs

    ReplaySubject<Object> subject = ReplaySubject.create();

    Observable.error(new RuntimeException("oops"))
        .materialize()
        .delay(1, TimeUnit.SECONDS)
        .dematerialize()
        .subscribe(subject);

    subject.subscribe();
    subject.materialize().toBlocking().first();

    System.out.println("Done");

where as

    ReplaySubject<Object> subject = ReplaySubject.create();

    Observable.error(new RuntimeException("oops"))
        .materialize()
        .delay(1, TimeUnit.SECONDS)
        .dematerialize()
        .subscribe(subject);

    subject.subscribe(n -> {}, e -> {});
    subject.materialize().toBlocking().first();

    System.out.println("Done");

does not.

[akarnokd]

The plain subscribe() has an onError handler which throws an OnErrorNotImplementedException and disrupts the event delivery inside the PublishSubject.

[vadims]

Is that by design?

[vadims]

@benjchristensen?

We're trying to see if we need to stop using subscribe() without an onError handler due to this behavior even when we don't need to handle the error notification.

[benjchristensen]

Yes, it is by design that if an error handler is not provided, but an error occurs it will throw OnErrorNotImplementedException. We never swallow errors automatically.

If you want to swallow an error prior to the subscribe you can do something like this:

stream.onErrorResumeNext(t -> Observable.empty()).subscribe();

The subscribe overloads that don't take an error handler assume you are handling the error cases in the stream, or that errors "won't happen".

[benjchristensen]

The hang may be that you're not seeing the OnErrorNotImplementedException be thrown due to the scheduling happening on delay: #1682

I haven't confirmed, but you should definitely see an exception be thrown somewhere.

[benjchristensen]

This one was kind of tricky ... I have to catch the error and wait until all subscribers receive the onError and then allow it to be thrown so that all subscribers are released.

Great bug. Thanks for reporting this.