The goal is to catch cases where the return value exists, but is
forgotten. There was a large enough number of them to turn this
into a real check. Initially, I just wanted to implement it to fix
the problems, then delete the code. But since this is so common, I
think it is worth the annoyance.
The reason is that if actions are provided by rules, only one instance
exist. It was a mistake to couple actions with their notifications. It
could not work reliably and has to be removed.
The commit also change the notification action storage to be a copy
instead of the original table. This allows to append actions (not part
of this commit) without risking adding them to the wrong notification.
**WARNING** This break an unreleased API by removing the `notification`
property of an action.
The current API is non-compliant with the 1.0 spec and cannot represent
the v1.2 spec at all. The pair of name and callback fails to represent
the explicit ordering and cannot support the icons cleanly.
Plus to support the keyboard navigation use case, the notification
action need to be able to get some sort of focus state. Having an
object makes this easy.
Emmanuel Lepage Vallee