Flowable.singleOrError() does not signal an exception if followed by flatMapPublisher

[jblatt1]

The following code demonstrates the expected behavior of Flowable.singleOrError() (as I understand it):

Flowable.empty()
    .singleOrError()
    .blockingGet(); // NoSuchElementException is thrown, as expected

However, if singleOrError() is immediately followed by Single.flatMapPublisher(...), the exception is lost:

Flowable.empty()
    .singleOrError()
    .flatMapPublisher(Flowable::just)
    .blockingSubscribe(); // No exception is thrown

Strangely, if anything is done between Flowable.singleOrError() and Single.flatMapPublisher(...), the exception is thrown as expected:

Flowable.empty()
    .singleOrError()
    .map(x -> x)
    .flatMapPublisher(Flowable::just)
    .blockingSubscribe(); // NoSuchElementException is thrown, as expected

This is with RxJava 2.1.10 and Reactive Streams 1.0.2.

[akarnokd]

Thanks for reporting and sharing code to reproduce the issue. The bug is in singleOrError triggered by a conversion back to toFlowable. Fix posted in #5904.