Single.flatMapPublisher full implementation

[davidmoten]

I noticed Single.flatMapPublisher is implemented as toFlowable().flatMapPublisher(...) which subjects the one flowable to batched requests. I'd like to have requests go straight through to the one flowable. Can I contribute this operator?

The operator at the moment is at https://github.com/davidmoten/rxjava2-http/blob/master/src/main/java/org/davidmoten/rx2/io/internal/FlowableSingleFlatMapPublisher.java without fusion. I can add more tests, fusion (transitive as per doOnEach) and follow the projects's naming and visibility conventions.

[akarnokd]

Sure.

[akarnokd]

In case you haven't started yet, you may want to wait for #6017 so the changes can be benchmarked.

[davidmoten]

That's brilliant, thanks

[davidmoten]

A question about fusion. I notice that timeout(Long, TimeUnit) doesn't support fusion and I suspect the operator I'm writing is similar. The problem is that a subscription is handed to downstream while the Single emission is being calculated and the resultant mapped Flowable is unknown. Just after the subscription is handed to downstream (via onSubscribe) requestFusion is called but of course at that point the fusion characteristics of the mapped Flowable is unknown and QueueFuseable.NONE is returned.

Should I chase fusion for this operator? Any suggestions?

[akarnokd]

Fusion won't work here due to the delayed subscription to the Flowable. Don't bother with it.

[davidmoten]

Righto, ta.