Properties aren't delivering the current value to multiple listeners

[Andersmholmgren]

The following prints

p1: first
p2: true
p1b: first

but should print

p1: first
p2: true
p1b: first
p2b: true

main() async {
  listen(Reactable r, String l) =>
      r.listen((v) => print('$l: $v'));

  final p1 = new Property.constant('first');
  final p2 = p1.map((s) => s == 'first').asProperty();

  listen(p1, 'p1');
  listen(p2, 'p2');

  await new Future.delayed(const Duration(milliseconds:100));

  listen(p1, 'p1b');
  listen(p2, 'p2b');

  await new Future.delayed(const Duration(milliseconds:100));
}

It seems that as map turns the property into a stream, the call to asProperty comes too late to save the value???

Incidentally it would be really nice if Property implemented map and returned a Property rather than needing to call asProperty(). Or maybe what is needed is another method with these semantics.

I find it is super common to derive properties from properties. In fact you could increasingly describe my whole app that way ;-)

[Dan Schultz]

Looks like the current value is not actually being delivered to multiple listeners. This only happens when you add a delay, because the listener is added in another event loop.

The test case can be simplified with this:

var p = new Property.constant(1).map((s) => s + 1);
p.listen(print);

new Future.delayed(new Duration(milliseconds: 100), () {
  p.listen(print);
});

I'll rename the ticket.