Re: [Caml-list] js_of_ocaml with node

[Alain Frisch <alain.frisch@lexifi.com>]

On 04/28/2015 09:53 AM, Alain Frisch wrote:
> val mkdir_async:
>      string ->
>      ?mode:(int[@js.default 0o777]) ->
>      (js_exn option -> unit) ->
>      unit
>    [@@js.global "fs.mkdir"]
>
>
> Here js.default forces the default value for the optional mode argument.
>   Without it, a missing value will send an `undefined` as the second
> argument (I don't know if fs.mkdir would be happy with it).

Just to clarify:  the issue here is that node.js documents the function as:

  fs.mkdir(path[, mode], callback)


and its implementation is more liberal:

=================
function modeNum(m, def) {
   if (util.isNumber(m))
     return m;
   if (util.isString(m))
     return parseInt(m, 8);
   if (def)
     return modeNum(def);
   return undefined;
}

fs.mkdir = function(path, mode, callback) {
   if (util.isFunction(mode)) callback = mode;
   ...
       modeNum(mode, 511 /*=0777*/)
   ...
};
=================

(welcome to Javascript wonderful calling conventions!)


So both conventions are supported to omit the mode argument:

   fs.mkdir(path, undefined, callback)
   fs.mkdir(path, callback)


(one could actually pass anything as the second argument as long as it 
is not a number, not a string and not a function).

So it is ok to bind it simply as:

val mkdir_async: string -> ?mode:int -> (js_exn option -> unit) ->  unit
   [@@js.global "fs.mkdir"]



Alain