RxJava 2.x Single is not extending Publisher

[balamaci]

Hi, I think Single should implement also org.reactivestreams.Publisher like Flowable.
Right now in io.reactivex.rxjava2 2.0.0 Single doesn't implement Publisher and this leads to being unable to do the following:

Flowable<String> colors = Flowable.fromArray("red", "green", "blue",
                "red", "yellow", "green", "green");

        Flowable<GroupedFlowable<String, String>> groupedColorsStream = colors
                                                                           .groupBy(val -> val);

        Flowable<Pair<String, Long>>
                countedColors = groupedColorsStream
                                        .flatMap(groupedFlow -> groupedFlow
                                                                    .count()
                                                                    .map(countVal -> new Pair<>(groupedFlow.getKey(), countVal))
                                        );
        countedColors.subscribe(System.out::println);

since count() returns Single, and flatMap has the signature:

    public final <R> Flowable<R> flatMap(Function<? super T, ? extends Publisher<? extends R>> mapper) {
        return this.flatMap(mapper, false, bufferSize(), bufferSize());
    }

[akarnokd]

It's not possible because of the receiver types are incompatible. Use toFlowable or flatMapSingle instead.

[balamaci]

Thanks for answering