Multiple child node fix

[mariusmuja]

Fixes a bug when there are multiple child nodes and only one emits.

On top of #130.

[fdietze]

Thanks for the fix!

I have to mention, that these kinds of annoyances only occur, because we abuse an event library to represent (UI) state. We need workarounds because we allow an inconsistent state to be defined in the first place (instead of requiring a default value in each variable). This results in inserting fake-content in the form of empty string-nodes or absent attributes which is not always the desired solution. If it is not totally clear what I'm saying here, please ask.

It is possible to define further, similarly failing tests.

  it should "partially render component even if parts not present" in {
    val messagesColor = PublishSubject[String]
    val messagesBgColor = PublishSubject[String]
    val childString = PublishSubject[String]

    val vNode = div(
      color <-- messagesColor,
      backgroundColor <-- messagesBgColor,
      child <-- childString
    )

    val node = document.createElement("div").asInstanceOf[html.Div]
    document.body.appendChild(node)
    OutWatch.renderInto(node, vNode).unsafeRunSync()

    node.innerHTML shouldBe "<div></div>"
    node.style.color shouldBe ""
    node.style.backgroundColor shouldBe ""

    childString.onNext("fish")
    node.innerHTML shouldBe "<div>fish</div>"
    node.style.color shouldBe ""
    node.style.backgroundColor shouldBe ""

    messagesColor.onNext("red")
    node.innerHTML shouldBe "<div>fish</div>"
    node.style.color shouldBe "red"
    node.style.backgroundColor shouldBe ""

    messagesBgColor.onNext("blue")
    node.innerHTML shouldBe "<div>fish</div>"
    node.style.color shouldBe "red"
    node.style.backgroundColor shouldBe "blue"
  }

We have to ask ourselves if this should be the desired behavior. What to do instead, or if we can forbid inconsistent state via the type system. For Monix, see monix/monix#279.

always related: #96