2.x: NPE at ObservableReplay.ReplayObserver.dispose()

[hvisser]

Stack trace below shows a crash that I unfortunately can't reproduce currently. I've checked the source for ObservableReplay.ReplayObserver and it looks like this can only happen if it's being disposed before being subscribed which sounds odd to me? What might be relevant is that unsubscribeOn() is used on the observable.

java.lang.NullPointerException: Attempt to invoke interface method 'void io.reactivex.disposables.Disposable.dispose()' on a null object reference
    at io.reactivex.internal.operators.observable.ObservableReplay$ReplayObserver.dispose(ObservableReplay.java:361)
    at io.reactivex.disposables.CompositeDisposable.dispose(CompositeDisposable.java:216)
    at io.reactivex.disposables.CompositeDisposable.dispose(CompositeDisposable.java:79)
    at io.reactivex.internal.operators.observable.ObservableRefCount$2.run(ObservableRefCount.java:126)
    at io.reactivex.disposables.RunnableDisposable.onDisposed(RunnableDisposable.java:28)
    at io.reactivex.disposables.RunnableDisposable.onDisposed(RunnableDisposable.java:18)
    at io.reactivex.disposables.ReferenceDisposable.dispose(ReferenceDisposable.java:42)
    at io.reactivex.internal.operators.observable.ObservableRefCount$ConnectionObserver.dispose(ObservableRefCount.java:181)
    at io.reactivex.internal.disposables.DisposableHelper.setOnce(DisposableHelper.java:79)
    at io.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeOnObserver.onSubscribe(ObservableSubscribeOn.java:58)
    at io.reactivex.internal.operators.observable.ObservableRefCount.doSubscribe(ObservableRefCount.java:113)
    at io.reactivex.internal.operators.observable.ObservableRefCount$1.accept(ObservableRefCount.java:98)
    at io.reactivex.internal.operators.observable.ObservableRefCount$1.accept(ObservableRefCount.java:92)
    at io.reactivex.internal.operators.observable.ObservableReplay.connect(ObservableReplay.java:305)
    at io.reactivex.internal.operators.observable.ObservableRefCount.subscribeActual(ObservableRefCount.java:68)
    at io.reactivex.Observable.subscribe(Observable.java:10514)
    at io.reactivex.internal.operators.observable.ObservableSubscribeOn$1.run(ObservableSubscribeOn.java:39)
    at io.reactivex.Scheduler$1.run(Scheduler.java:134)
    at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:59)
    at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:51)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:272)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
    at java.lang.Thread.run(Thread.java:761)

[akarnokd]

Thanks for reporting, this is a bug. What happens is that the asnyc dispose happens before the chain of onSubscribe call reaches the operator. The same happens inside FlowableReplay. I'll post a fix shortly.

[akarnokd]

See #5064

[akarnokd]

Closing via #5064