Type unsoundness in ModuleHooks

[raquo]

Our hooks have correct types except for one edge case, when the hooks for the initial app container are processed. Snabbdom creates a virtual empty node for the first argument of patch method when it's a real DOM element, and that empty virtual node is not an instance of our own Node class but a plain JS object which although has a similar shape will be missing any additional fields and methods defined in Scala. This is especially a problem for libraries based on Snabbdom.scala that subclass Node and NodeData.

There are a couple ways to fix that. One is to make the types reflect this reality. Another is to keep current types but avoid calling Scala-provided hook on the snabbdom-created node in that edge case.

I kinda favour the latter option because we will probably not lose anything of significance, but it would be a departure from Snabbdom.js API, so needs to be considered more carefully. Which is why this is not yet resolved.