RList.make_from_s cannot be used within update step

[mfp]

make_from_s uses React.S.value, which can raise a Failure when executed within an update step. I haven't been able to define it using only React non-primitive operators. Even though coping out to a concurrency monad does work, it's not desirable here since it'd introduce a new dependency (and force the user's hand in deciding between Lwt/async/other).

Similarly, all the imperative operations on the handle are unsafe within an update step -- this should at least be documented.

[pveber]

I just hit the same issue (the function is now named RList.from_signal). IMHO this is a serious issue, since it basically prevents in eliom to define a reactive element that creates reactive parts itself.

[balat]

@hhugo Do you have an idea about this?