onChange doesn't fire on initial render

[meirish]

I'm not sure if this is related to #10 or not, but we recently found that a hard refresh of our app on a page that renders at least one portal does not call the onChange function that's passed to PortalTarget. We worked around this by moving our updating to use the yielded count which does have the right value.

Is this a bug or intended behavior?

[simonihmig]

Hm, sounds like a bug. Thanks for reporting!

There is a test for onChange, but it is only covering the delayed case, not an initial render that already has an active portal.

If you have the time, a PR with such a (failing) test case would help!