Fix trailing undefined for optional parameters not omitted with @send

jscomp/core/lam_compile_external_call.ml

@@ -250,6 +250,16 @@ let translate_scoped_access scopes obj =
  | [] -> obj
  | x :: xs -> Ext_list.fold_left xs (E.dot obj x) E.dot
 
+let keep_non_undefined_args args arg_types =
+ let rec aux argsList (argTypes : specs) =
+ match (argsList, argTypes) with
+ | ( {J.expression_desc = Undefined {isUnit = false}; _} :: rest,
+ {External_arg_spec.arg_label = Arg_optional; _} :: argTypes ) ->
+ aux rest argTypes
+ | _ -> argsList
+ in
+ aux (List.rev args) (List.rev arg_types) |> List.rev
+
 let translate_ffi (cxt : Lam_compile_context.t) arg_types
  (ffi : External_ffi_types.external_spec) (args : J.expression list) ~dynamic_import =
  match ffi with
@@ -271,16 +281,7 @@ let translate_ffi (cxt : Lam_compile_context.t) arg_types
  else E.call ~info:{ arity = Full; call_info = Call_na } fn args)
  else
  let args, eff = assemble_args_no_splice arg_types args in
- let rec keepNonUndefinedArgs argsList (argTypes : specs) =
- match (argsList, argTypes) with
- | ( {J.expression_desc = Undefined {isUnit = false}; _} :: rest,
- {External_arg_spec.arg_label = Arg_optional; _} :: argTypes ) ->
- keepNonUndefinedArgs rest argTypes
- | _ -> argsList
- in
- let args =
- keepNonUndefinedArgs (List.rev args) (List.rev arg_types) |> List.rev
- in
+ let args = keep_non_undefined_args args arg_types in
  add_eff eff
  @@ E.call ~info:{ arity = Full; call_info = Call_na } fn args
  | Js_module_as_fn { external_module_name; splice } ->
@@ -341,6 +342,7 @@ let translate_ffi (cxt : Lam_compile_context.t) arg_types
  (E.dot self name) args)
  else
  let args, eff = assemble_args_no_splice arg_types args in
+ let args = keep_non_undefined_args args arg_types in
  add_eff eff
  (let self = translate_scoped_access js_send_scopes self in
  E.call

jscomp/test/omit_trailing_undefined_in_external_calls.res

@@ -9,3 +9,7 @@ external formatDate: (Js.Date.t, ~options: dateFormatOptions=?, ~done: bool=?) =
 let x = formatDate(Js.Date.make())
 let x = formatDate(Js.Date.make(), ~options={someOption: true})
 let x = formatDate(Js.Date.make(), ~done=true)
+
+@send external toString: (float, ~radix: int=?) => string = "toString"
+
+let x = toString(42.)