[BUG] Cannot parse file (trailing comma)

[giltho]

Describe the bug
I'm getting an error when compiling a projet :

Error: cannot parse file "path/to/harfbuzz.js"
(orig:"path/to/harfbuzz.js" from l:3, c:0)

this file contains

// Provides: rehb_new_face
function rehb_new_face(
  _fontName /*: string */,
) {
  return undefined;
}

// Provides: rehb_shape
// Requires: caml_to_js_string
function rehb_shape(_face /*: fk_face */, text /*: string */) {
  var str = caml_to_js_string(text);
  var ret = str.split("").map(function mapper(_char) {
      return [/* <jsoo_empty> */ 0, /* glyphId */ 0, /* cluster */ 0];
    });

  // Adding the leading `0` to make it a jsoo compatible array
  ret.unshift(0);
  return ret;
}

I'm thinking this might already have been fixed by #980 , so I tried to pin the latest commit (203dc9c), but I get a new error. I cannot even build js_of_ocaml-compiler anymore, and the dependency build fails with

running: 'dune' 'build' '-p' 'js_of_ocaml-compiler' '-j' '4'
           ocaml (internal)
    ocamlfind: Package `graphics' not found
           ocaml (internal) (exit 2)

Versions
ocaml: 4.08.1
js_of_ocaml: 3.5.2

[hhugo]

Well, it seems there is indeed a syntax error. Why do you have trailing comma _fontName /*: string */, ?

[giltho]

The file comes from here
https://github.com/revery-ui/reason-harfbuzz/blob/master/src/harfbuzz.js

If I was to guess, this looks like the output of a JS formatter like prettier. Trailing commas for multi-line function parameters are useful so you don't have to modify the previous line when adding a new parameter, and it's correct syntax in ES2017.

I don't really know what's the policy of js_of_ocaml here

[giltho]

I didn't realise it was because of the trailing comma though, I created a PR for reason-harfbuzz to remove the trailing comma

[hhugo]

The JavaScript parser inside js_of_ocaml didn't keep up with recent version of ecmascript. One could update the parser. PR welcome.