onNext not called if onError is called immediately after when Scheduler is defined in observeOn

If I set a Scheduler in .observeOn(...) for an Observable and call subscriber.onError immediately after subscriber.onNext, onNext is never called in my Observer.

If I either add a sleep between subscriber.onNext and subscriber.onError or don’t set a Scheduler in .observeOn(...), onNext is called in my Observer.

See example:

Observable.create(new Observable.OnSubscribe<String>() {
    @Override
    public void call(Subscriber<? super String> subscriber) {
        subscriber.onNext("Test");
        subscriber.onError(null);
    }
}).observeOn(AndroidSchedulers.mainThread())
        .subscribe(new Observer<String>() {
            @Override
            public void onCompleted() {
                System.out.println("onCompleted");
            }

            @Override
            public void onError(Throwable e) {
                System.out.println("onError");
            }

            @Override
            public void onNext(String s) {
                System.out.println("onNext");
            }
        });

// Only prints "onError", but should print "onNext" and then "onError"

[larryng]

Note to future self because I know I’m going to forget this (again): you can use .observeOn(Scheduler scheduler, boolean delayError) to ensure onNext isn’t skipped by onError.

[akarnokd]

Something like this:

Observable.create(new Observable.OnSubscribe<String>() {
    @Override
    public void call(Subscriber<? super String> subscriber) {
        subscriber.onNext("Test");
        subscriber.onError(null);
    }
}).materialize().observeOn(AndroidSchedulers.mainThread()).<String>dematerialize()
        .subscribe(new Observer<String>() {
            @Override
            public void onCompleted() {
                System.out.println("onCompleted");
            }

            @Override
            public void onError(Throwable e) {
                System.out.println("onError");
            }

            @Override
            public void onNext(String s) {
                System.out.println("onNext");
            }
        });