RxJava1 vs Rxjava2: Exception in onNext

Question

When doing the following in RxJava1, the exception in onNext would be re-routed into the same Subscriber's onError:

    Observable.from(Arrays.asList("1", "22", "333", "4444")).subscribe(new Subscriber<String>() {
        @Override
        public void onCompleted() {

        }

        @Override
        public void onError(Throwable e) {
            Log.d("RxJava1", "onError: " + e.getCause());
        }

        @Override
        public void onNext(String s) {
            if (s.length() == 4) {
                Integer test = null;
                test.hashCode();
            }
            Log.d("RxJava1", s + " - " + s.length());
        }
    });

output:

D/RxJava1: 1 - 1
D/RxJava1: 22 - 2
D/RxJava1: 333 - 3
D/RxJava1: onError: null

When doing, as far as I know, the same in RxJava2, this behaviour has changed and no longer returns to onError, but simply crashes:

    Observable.fromIterable(Arrays.asList("1", "22", "333", "4444")).subscribeWith(new Observer<String>() {
        @Override
        public void onSubscribe(Disposable d) {

        }

        @Override
        public void onNext(String s) {
            if (s.length() == 4) {
                Integer test = null;
                test.hashCode();
            }
            Log.d("RxJava2", s + " - " + s.length());
        }

        @Override
        public void onError(Throwable e) {
            Log.d("RxJava2", "onError: " + e.getCause());
        }

        @Override
        public void onComplete() {

        }
    });

Output:

D/RxJava2: 1 - 1
D/RxJava2: 22 - 2
D/RxJava2: 333 - 3
D/AndroidRuntime: Shutting down VM

I'd mostly like to know, which of the 2 versions is doing it "wrong"? Was this a bug in RxJava1 that has been fixed? Is this a bug in RxJava2? Or has this not been a conscious change in the first place, since I can't find any details about this?

ps. I did notice that wrapping this into 'SafeObserver' re-routes to onError again

Answer 1

Neither is wrong, the two versions have different design constraints. In 2.x the Observer/Subscriber can't throw from its onXXX methods.

If you use the 1-2-3 argument subscribe() methods in 2.x you are covered. Otherwise if you really can't fix your onNext use safeSubscribe().