Since ee956a197, the rendering is skipped if the currentFiber is
completed. Unfortunately, cancelled fibers remain set in __owl__,
so when a fiber is cancelled, subsequent calls to render are
skipped.
It would be nice to reset __owl__.currentFiber to null when the
fiber is cancelled, but when trying to do so, a lot of tests fail.
Part of issue #622Closes#665
Asynchronous rendering is subtle. Before this commit, it was possible
(though not easy) to get into a situation where the Owl rendering
pipeline decremented twice the counter of a fiber that indicates that
its work is complete.
The situation occurs in the `render` method, where we create a fiber,
wait for a micro tick before starting the actual rendering (the goal was
to batch all changes coming from a single call stack). However, in this
microtask tick, it was possible that the fiber was cancelled, and we did
not have a check for that.
In most cases, we just want Component<any, Env>. But since it was so
annoying to have always the type Env, we actually used
Component<any,any> everywhere.
With this commit, the generic types have a default (and their order is
swapped), so we can simply use Component in most cases, and
Component<Props> when we want to type the props.
Géry Debongnie