Channels decoration depends on the way messages are produced

[marekczajkowski]

Is there a specific rationale for invoking the decorate method on publishers based on the method of message publication? I observed that when producing messages with Multi, the decorator does not get triggered, whereas it works when producing a Multi of payloads or using PublisherBuilder.

This works fine - Decorator is called:

@Outgoing("source")
  public PublisherBuilder<Message<String>> source() {
    return ReactiveStreams.of("Hello", "from", "SmallRye", "world").map(Message::of);
  }

as well as

@Outgoing("source")
  public Multi<String> source() {
    return Multi.createFrom().items("Hello", "from", "SmallRye", "world");
  }

But not here:

@Outgoing("source")
  public Multi<Message<String>> source() {
    return Multi.createFrom().items("Hello", "from", "SmallRye", "world").map(Message::of);
  }

It looks like it when PublisherMediator is creating publishers for some of them decorate is not called

   private void produceAPublisherBuilderOfMessages() {
        PublisherBuilder<Message<?>> builder = invoke();
        this.publisher = decorate(MultiUtils.publisher(AdaptersToFlow.publisher(builder.buildRs())));
    }

    private <P> void produceAPublisherBuilderOfPayloads() {
        PublisherBuilder<P> builder = invoke();
        this.publisher = decorate(MultiUtils.publisher(AdaptersToFlow.publisher(builder.map(Message::of).buildRs())));
    }

    private void produceAPublisherOfMessages() {
        Flow.Publisher<Message<?>> pub = invoke();
        this.publisher = MultiUtils.publisher(pub);
    }

    private void produceAReactiveStreamsPublisherOfMessages() {
        Publisher<Message<?>> pub = invoke();
        this.publisher = MultiUtils.publisher(AdaptersToFlow.publisher(pub));
    }

    private <P> void produceAPublisherOfPayloads() {
        Flow.Publisher<P> pub = invoke();
        this.publisher = decorate(MultiUtils.publisher(pub).map(Message::of));
    }

    private <P> void produceAReactiveStreamsPublisherOfPayloads() {
        Publisher<P> pub = invoke();
        this.publisher = decorate(Multi.createFrom().publisher(AdaptersToFlow.publisher(pub)).map(Message::of));
    }

Is this behavior a bug, or is there a justification for it?

[michalcukierman]

If it's intentional, should we propose a Decorators documentation update, so it's not confusing?