Rescript-compiler: Ideas: wrap null into option automatically

[bobzhang]

extenral match_ : string -> Js.Re.t -> (string array option [@bs.null])

[OvermindDL1]

That would indeed be quite nice, undefined would still be standalone though?

[bobzhang]

@OvermindDL1 I think we make it more general to justify its inclusion

external get : t -> int -> int = "" [@@bs.index]
[@@bs.return { throw_if_null = "error message $0 $1 $2" ; 
                          throw_if_undefined = "xx" ;
                          (* option_if_null ; option_if_undefined ;
                              warn_if_null; warn_if_undefined
                         *) (* these flags are not compatible with [throw]*)
}]

The cool thing is that we can turn on [throw_if_null], [throw_if_undefined] for _FFIs in debug mode_, that will help find FFI bugs quickly.

[bobzhang]

Note we can make the post-assertion a little more general like

type_is_string ? type_is_int? type_is_number? 

Or do it in a best effort style, by doing a console.warn

[bobzhang]

This would be also useful to check nan some JS API, returns either int or nan
For the return value we can also convert it from Js.boolean to bool. So that
user can just write Js.Float.isFinite

[stale[bot]]

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