js_dump.ml

(* BuckleScript compiler
 * Copyright (C) 2015-2016 Bloomberg Finance L.P.
 * http://www.ocsigen.org/js_of_ocaml/
 * Copyright (C) 2010 Jérôme Vouillon
 * Laboratoire PPS - CNRS Université Paris Diderot
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, with linking exception;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*)
(* Authors: Jérôme Vouillon, Hongbo Zhang  *)

(*
  http://stackoverflow.com/questions/2846283/what-are-the-rules-for-javascripts-automatic-semicolon-insertion-asi
  ASI catch up
   {[
     a=b
       ++c
       ---
       a=b ++c
     ====================
     a ++
     ---
     a
     ++
     ====================
     a --
     ---
     a
     --
     ====================
     (continue/break/return/throw) a
     ---
     (continue/break/return/throw)
       a
     ====================
   ]}

*)


module P = Ext_pp
module E = Js_exp_make
module S = Js_stmt_make

module L = Js_dump_lit
let return_indent = (String.length L.return / Ext_pp.indent_length)

let throw_indent = (String.length L.throw / Ext_pp.indent_length)


let semi f = P.string f L.semi

let op_prec, op_str  =
  Js_op_util.(op_prec, op_str)


let rec comma_idents  cxt f (ls : Ident.t list)  =
  match ls with
  | [] -> cxt
  | [x] -> Ext_pp_scope.ident cxt f x
  | y :: ys ->
    let cxt = Ext_pp_scope.ident cxt f y in
    P.string f L.comma;
    comma_idents cxt f ys
let ipp_ident cxt f id un_used =
  if un_used then
    Ext_pp_scope.ident cxt f (Ext_ident.make_unused ())
  else
    Ext_pp_scope.ident cxt f id
let rec formal_parameter_list cxt (f : P.t) method_ l env =
  let offset = if method_ then 1 else 0 in
  let rec aux i cxt l =
    match l with
    | []     -> cxt
    | [id]    -> ipp_ident cxt f id (Js_fun_env.get_unused env i)
    | id :: r ->
      let cxt = ipp_ident cxt f id (Js_fun_env.get_unused env i) in
      P.string f L.comma; P.space f;
      aux (i + 1) cxt  r
  in
  match l with
  | [] -> cxt
  | [i] ->
    (** necessary, since some js libraries like [mocha]...*)
    if Js_fun_env.get_unused env offset then cxt
    else
      Ext_pp_scope.ident cxt f i
  | _ ->
    aux offset cxt l


(* IdentMap *)
(*
f/122 -->
  f/122 is in the map
  if in, use the old mapping
  else
    check  f,
     if in last bumped id
     else
        use "f", register it

  check "f"
         if not , use "f", register stamp -> 0
         else
           check stamp
             if in  use it
             else check last bumped id, increase it and register
*)
type name =
  | No_name
  | Name_top  of Ident.t
  | Name_non_top of Ident.t


(**
   Turn [function f (x,y) { return a (x,y)} ] into [Curry.__2(a)],
   The idea is that [Curry.__2] will guess the arity of [a], if it does
   hit, then there is no cost when passed
*)


(* TODO: refactoring
   Note that {!pp_function} could print both statement and expression when [No_name] is given
*)
let rec

  try_optimize_curry cxt f len function_id =
  begin
    P.string f Js_runtime_modules.curry;
    P.string f L.dot;
    P.string f "__";
    P.string f (Printf.sprintf "%d" len);
    P.paren_group f 1 (fun _ -> expression 1 cxt f function_id  )
  end

and  pp_function method_
    cxt (f : P.t) ?(name=No_name)  return
    (l : Ident.t list) (b : J.block) (env : Js_fun_env.t ) =
  match b, (name,  return)  with
  | [ {statement_desc =
         Return {return_value =
                   {expression_desc =
                      Call(({expression_desc = Var v ; _} as function_id),
                           ls ,
                           {arity = ( Full | NA as arity(* see #234*));
                            (* TODO: need a case to justify it*)
                            call_info =
                              (Call_builtin_runtime | Call_ml )})}}}],
    ((_, false) | (No_name, true))
    when
      (* match such case:
         {[ function(x,y){ return u(x,y) } ]}
         it can be optimized in to either [u] or [Curry.__n(u)]
      *)
      not method_ &&
      Ext_list.for_all2_no_exn (fun a (b : J.expression) ->
          match b.expression_desc with
          | Var (Id i) -> Ident.same a i
          | _ -> false) l ls ->
    let optimize  len p cxt f v =
      if p then try_optimize_curry cxt f len function_id
      else
        vident cxt f v
    in
    let len = List.length l in (* length *)
    begin match name with
      | Name_top i | Name_non_top i  ->
        P.string f L.var;
        P.space f ;
        let cxt = Ext_pp_scope.ident cxt f i in
        P.space f ;
        P.string f L.eq;
        P.space f ;
        let cxt = optimize len (arity = NA && len <= 8) cxt f v in
        semi f ;
        cxt
      | No_name ->
        if return then
          begin
            P.string f L.return ;
            P.space f
          end;
        optimize len (arity = NA && len <=8) cxt f v

    end
  | _, _  ->

    let set_env : Ident_set.t = (** identifiers will be printed following*)
      match name with
      | No_name ->
        Js_fun_env.get_unbounded env
      | Name_top id | Name_non_top id -> Ident_set.add id (Js_fun_env.get_unbounded env )
    in
    (* the context will be continued after this function *)
    let outer_cxt = Ext_pp_scope.merge set_env cxt in

    (* the context used to be printed inside this function

       when printing a function,
       only the enclosed variables and function name matters,
       if the function does not capture any variable, then the context is empty
    *)
    let inner_cxt = Ext_pp_scope.sub_scope outer_cxt set_env in


    (* (if not @@ Js_fun_env.is_empty env then *)
    (* pp_comment  f (Some (Js_fun_env.to_string env))) ; *)
    let param_body () =
      if method_ then begin
        let cxt = P.paren_group f 1 (fun _ ->
            formal_parameter_list inner_cxt  f method_ (List.tl l) env )
        in
        P.space f ;
        ignore @@ P.brace_vgroup f 1 (fun _ ->
            let cxt =
              if not (Js_fun_env.get_unused env 0) then
                begin
                  P.string f L.var ;
                  P.space f;
                  let cxt = Ext_pp_scope.ident cxt f (List.hd l) in
                  P.space f ;
                  P.string f L.eq ;
                  P.space f ;
                  P.string f L.this;
                  P.space f ;
                  semi f ;
                  P.newline f ;
                  cxt ;
                end
              else
                cxt
            in
            statement_list false cxt f b
          );

      end
      else begin
        let cxt = P.paren_group f 1 (fun _ ->
            formal_parameter_list inner_cxt  f method_ l env )
        in
        P.space f ;
        ignore @@ P.brace_vgroup f 1 (fun _ -> statement_list false cxt f b );
      end
    in
    let lexical : Ident_set.t = Js_fun_env.get_lexical_scope env in
    let enclose  lexical  return =
      let handle lexical =
        if  Ident_set.is_empty lexical
        then
          begin
            if return then
              begin
                P.string f L.return ;
                P.space f
              end ;

            begin match name with
              | No_name ->
                (* see # 1692, add a paren for annoymous function for safety  *)
                P.paren_group f 1 begin fun _ ->
                  P.string f L.function_;
                  P.space f ;
                  param_body ()
                end
              | Name_non_top x  ->
                P.string f L.var ;
                P.space f ;
                ignore @@ Ext_pp_scope.ident inner_cxt f x ;
                P.space f ;
                P.string f L.eq ;
                P.space f ;
                P.string f L.function_;
                P.space f ;
                param_body ();
                semi f ;
              | Name_top x  ->
                P.string f L.function_;
                P.space f ;
                ignore (Ext_pp_scope.ident inner_cxt f x);
                param_body ();
            end;
          end
        else
          (* print as
             {[(function(x,y){...} (x,y))]}
          *)
          let lexical = Ident_set.elements lexical in
          (if return then
             begin
               P.string f L.return ;
               P.space f
             end
           else
             begin match name with
               | No_name -> ()
               | Name_non_top name | Name_top name->
                 P.string f L.var;
                 P.space f;
                 ignore @@ Ext_pp_scope.ident inner_cxt f name ;
                 P.space f ;
                 P.string f L.eq;
                 P.space f ;
             end
          )
          ;
          P.string f L.lparen;
          P.string f L.function_;
          P.string f L.lparen;
          ignore @@ comma_idents inner_cxt f lexical;
          P.string f L.rparen;
          P.brace_vgroup f 0  (fun _ ->
              begin
                P.string f L.return ;
                P.space f;
                P.string f L.function_;
                P.space f ;
                (match name with
                 | No_name  -> ()
                 | Name_non_top x | Name_top x -> ignore (Ext_pp_scope.ident inner_cxt f x));
                param_body ()
              end);
          P.string f L.lparen;
          ignore @@ comma_idents inner_cxt f lexical;
          P.string f L.rparen;
          P.string f L.rparen;
          begin match name with
            | No_name -> () (* expression *)
            | _ -> semi f (* has binding, a statement *)
          end
      in
      begin match name with
        | Name_top name | Name_non_top name  when Ident_set.mem name lexical ->
          (*TODO: when calculating lexical we should not include itself *)
          let lexical =  (Ident_set.remove name lexical) in
          handle lexical
        | _ -> handle lexical
      end
    in
    enclose lexical return
    ;
    outer_cxt


(* Assume the cond would not change the context,
    since it can be either [int] or [string]
*)
and pp_one_case_clause : 'a .
  _ -> P.t -> (P.t -> 'a -> unit) -> 'a J.case_clause -> _
  = fun cxt f  pp_cond
    ({switch_case = switch_case; switch_body = (switch_body,should_break)} : _ J.case_clause) ->
    let cxt =
      P.group f 1  (fun _ ->
          P.group f 1 (fun _ ->
              P.string f L.case;
              P.space f ;
              pp_cond  f switch_case; (* could be integer or string *)
              P.space f ;
              P.string f L.colon  );
          P.space f;
          P.group f 1 (fun _ ->
              let cxt =
                match switch_body with
                | [] -> cxt
                | _ ->
                  P.newline f ;
                  statement_list false cxt  f switch_body
              in
              (if should_break then
                 begin
                   P.newline f ;
                   P.string f L.break;
                   semi f;
                 end) ;
              cxt))
    in
    P.newline f;
    cxt

and loop_case_clauses  :  'a . Ext_pp_scope.t ->
  P.t -> (P.t -> 'a -> unit) -> 'a J.case_clause list -> Ext_pp_scope.t
  = fun  cxt  f pp_cond cases ->
    match cases with
    | [] -> cxt
    | [x] -> pp_one_case_clause cxt f pp_cond x
    | x::xs ->
      let cxt = pp_one_case_clause cxt f pp_cond x
      in loop_case_clauses  cxt f pp_cond  xs

and vident cxt f  (v : J.vident) =
  begin match v with
    | Id v | Qualified(v, _, None) ->
      Ext_pp_scope.ident cxt f v
    | Qualified (id, (Ml | Runtime),  Some name) ->
      let cxt = Ext_pp_scope.ident cxt f id in
      P.string f L.dot;
      P.string f (Ext_ident.convert  name);
      cxt
    | Qualified (id, External _, Some name) ->
      let cxt = Ext_pp_scope.ident cxt f id in
      Js_dump_property.property_access f name ;
      cxt

  end

and expression l cxt  f (exp : J.expression) : Ext_pp_scope.t =
  pp_comment_option f exp.comment ;
  expression_desc cxt l f exp.expression_desc

and
  expression_desc cxt (l:int) f x : Ext_pp_scope.t  =
  match x with
  | Var v ->
    vident cxt f v
  | Bool b ->
    (if  b then P.string f L.true_ else P.string f L.false_ ) ; cxt
  | Seq (e1, e2) ->
    let action () =
      let cxt = expression 0 cxt f e1 in
      P.string f L.comma ;
      P.space f ;
      expression 0 cxt f e2  in
    if l > 0 then
      P.paren_group f 1 action
    else action ()

  | Fun (method_, l, b, env) ->  (* TODO: dump for comments *)
    pp_function method_ cxt f false  l b env
  (* TODO:
     when [e] is [Js_raw_code] with arity
     print it in a more precise way
     It seems the optimizer already did work to make sure
     {[
       Call (Raw_js_code (s, Exp i), el, {Full})
       when Ext_list.length_equal el i
     ]}
  *)

  | Call (e, el, info) ->
    let action () =
      P.group f 1 (fun _ ->
          match info, el  with
          | {arity  = Full }, _
          | _, [] ->
            let cxt = expression 15 cxt f e in
            P.paren_group f 1 (fun _ -> arguments cxt  f el )

          | _ , _ ->
            (* ipp_comment f (Some "!") *)
            P.string f  Js_runtime_modules.curry;
            P.string f L.dot;
            let len = List.length el in
            if 1 <= len && len <= 8 then
              begin
                P.string f L.app;
                P.string f (Printf.sprintf "%d" len);
                P.paren_group f 1 (fun _ -> arguments cxt f (e::el))
              end
            else
              begin
                P.string f  L.app_array;
                P.paren_group f 1
                  (fun _ -> arguments cxt f [ e ; E.array Mutable el])
              end)
    in
    if l > 15 then P.paren_group f 1 action
    else action ()
  | Bind (a,b) ->
    (* a.bind(b)
       {[ fun b -> a.bind(b) ==? a.bind ]}
    *)
    begin
      expression_desc cxt l f
        (Call ({expression_desc = Dot(a,L.bind, true); comment = None }, [b],
               {arity = Full; call_info = Call_na}))
    end

  | FlatCall(e,el) ->
    P.group f 1 (fun _ ->
        let cxt = expression 15 cxt f e in
        P.string f L.dot;
        P.string f L.apply;
        P.paren_group f 1 (fun _ ->
            P.string f L.null;
            P.string f L.comma;
            P.space f ;
            expression 1 cxt f el
          )
      )
  | String_of_small_int_array ({expression_desc = desc } as e) ->
    let action () =
      P.group f 1 (fun _ ->
          P.string f L.string_cap;
          P.string f L.dot ;
          P.string f L.fromCharcode;
          begin match desc with
            | Array (el, _mutable)
              ->
              P.paren_group f 1 (fun _ -> arguments cxt f el)
            | _ ->
              P.string f L.dot ;
              P.string f L.apply;
              P.paren_group f 1 (fun _ ->
                  P.string f L.null;
                  P.string f L.comma;
                  expression 1 cxt  f e  )
          end )
    in
    if l > 15 then P.paren_group f 1 action
    else action ()


  | Array_append (e, el) ->
    P.group f 1 (fun _ ->
        let cxt = expression 15 cxt f e in
        P.string f ".concat";
        P.paren_group f 1 (fun _ -> arguments cxt f [el]))

  | Array_copy e ->
    P.group f 1 (fun _ ->
        let cxt = expression 15 cxt f e in
        P.string f ".slice";
        P.string f "()" ;
        cxt
      )

  | Dump (level, el) ->
    let obj =
      match level with
      | Log -> "log"
      | Info -> "info"
      | Warn -> "warn"
      | Error -> "error" in
    P.group f 1 (fun _ ->
        P.string f L.console;
        P.string f L.dot;
        P.string f obj ;
        P.paren_group f 1 (fun _ -> arguments cxt f el))
  | Json_stringify e
    ->
    P.group f 1 (fun _ ->
        P.string f L.json ;
        P.string f L.dot;
        P.string f L.stringify;
        P.paren_group f 1 (fun _ -> expression 0 cxt f e )
      )
  | Char_to_int e ->
    begin match e.expression_desc with
      | String_access (a,b) ->
        P.group f 1 (fun _ ->
            let cxt = expression 15 cxt f a in
            P.string f L.dot;
            P.string f L.char_code_at;
            P.paren_group f 1 (fun _ -> expression 0 cxt f b);
          )
      | _ ->
        P.group f 1 (fun _ ->
            let cxt = expression 15 cxt f e in
            P.string f L.dot;
            P.string f L.char_code_at;
            P.string f "(0)";
            cxt)
    end

  | Char_of_int e ->
    P.group f 1 (fun _ ->
        P.string f L.string_cap;
        P.string f L.dot;
        P.string f L.fromCharcode;
        P.paren_group f 1 (fun _ -> arguments cxt f [e])
      )


  | Math (name, el) ->
    P.group f 1 (fun _ ->
        P.string f L.math;
        P.string f L.dot;
        P.string f name;
        P.paren_group f 1 (fun _ -> arguments cxt f el)
      )
  | Unicode s ->
    P.string f "\"";
    P.string f s ;
    P.string f "\"";
    cxt
  | Str (_, s) ->
    (*TODO --
       when utf8-> it will not escape '\\' which is definitely not we want
    *)
    Js_dump_string.pp_string f  s;
    cxt

  | Raw_js_code (s,info) ->
    begin match info with
      | Exp ->
        P.string f "(";
        P.string f s ;
        P.string f ")";
        cxt
      | Stmt ->
        P.newline f  ;
        P.string f s ;
        P.newline f ;
        cxt
    end
  | Number v ->
    let s =
      match v with
      | Float {f = v} ->
        Js_number.caml_float_literal_to_js_string v
      (* attach string here for float constant folding?*)
      | Int { i = v; _}
        -> Int32.to_string v (* check , js convention with ocaml lexical convention *)
      | Uint i
        -> Format.asprintf "%lu" i
      | Nint i -> Nativeint.to_string i
    in
    let need_paren =
      if s.[0] = '-'
      then l > 13  (* Negative numbers may need to be parenthesized. *)
      else l = 15  (* Parenthesize as well when followed by a dot. *)
           && s.[0] <> 'I' (* Infinity *)
           && s.[0] <> 'N' (* NaN *)
    in
    let action = fun _ -> P.string f s  in
    (
      if need_paren
      then P.paren f  action
      else action ()
    );
    cxt
  | J.Anything_to_number e
    ->
    let action () =
      P.group f 0 @@ fun _ ->
      P.string f "+" ;
      expression 13 cxt f e
    in
    (* need to tweak precedence carefully
       here [++x --> +(+x)]
    *)
    if l > 12
    then P.paren_group f 1 action
    else action ()
  | Is_null_undefined_to_boolean e ->
    let action = (fun _ ->
        let cxt = expression 1 cxt f e in
        P.space f ;
        P.string f "==";
        P.space f ;
        P.string f L.null;
        cxt)  in
    if l > 0 then
      P.paren_group f 1 action
    else action ()

  | Caml_not e
  | Js_not e ->
    let action () =
      P.string f "!" ;
      expression 13 cxt f e
    in
    if l > 13
    then P.paren_group f 1 action
    else action ()
  | Typeof e
    ->
    P.string f "typeof";
    P.space f;
    expression 13 cxt f e
  | Caml_block_set_tag(a,b) ->
    expression_desc cxt l f
      (Bin(Eq,
           {expression_desc = Caml_block_tag a; comment = None},
           b
          ))
  | Caml_block_set_length(a,b) ->
    expression_desc cxt l f
      (Bin(Eq,
           {expression_desc = Length (a,Caml_block); comment = None},
           b
          ))
  | Bin (Eq, {expression_desc = Var i },
         {expression_desc =
            (
              Bin(
                (Plus as op), {expression_desc = Var j}, delta)
            | Bin(
                (Plus as op), delta, {expression_desc = Var j})
            | Bin(
                (Minus as op), {expression_desc = Var j}, delta)
            )
         })
    when Js_op_util.same_vident i j ->
    (* TODO: parenthesize when necessary *)
    begin match delta, op with
      | {expression_desc = Number (Int { i =  1l; _})}, Plus
      (* TODO: float 1. instead,
           since in JS, ++ is a float operation
      *)
      | {expression_desc = Number (Int { i =  -1l; _})}, Minus
        ->
        P.string f L.plusplus;
        P.space f ;
        vident cxt f i

      | {expression_desc = Number (Int { i =  -1l; _})}, Plus
      | {expression_desc = Number (Int { i =  1l; _})}, Minus
        ->
        P.string f L.minusminus;
        P.space f ;
        vident cxt f i;
      | _, _ ->
        let cxt = vident cxt f i in
        P.space f ;
        if op = Plus then P.string f "+="
        else P.string f "-=";
        P.space f ;
        expression 13 cxt  f delta
    end
  | Bin (Eq, {expression_desc = Access({expression_desc = Var i; _},
                                       {expression_desc = Number (Int {i = k0 })}
                                      ) },
         {expression_desc =
            (Bin((Plus as op),
                 {expression_desc = Access(
                      {expression_desc = Var j; _},
                      {expression_desc = Number (Int {i = k1; })}
                    ); _}, delta)
            | Bin((Plus as op), delta,
                  {expression_desc = Access(
                       {expression_desc = Var j; _},
                       {expression_desc = Number (Int {i = k1; })}
                     ); _})
            | Bin((Minus as op),
                  {expression_desc = Access(
                       {expression_desc = Var j; _},
                       {expression_desc = Number (Int {i = k1; })}
                     ); _}, delta)

            )})
    when  k0 = k1 && Js_op_util.same_vident i j
    (* Note that
       {[x = x + 1]}
       is exactly the same  (side effect, and return value)
       as {[ ++ x]}
       same to
       {[ x = x + a]}
       {[ x += a ]}
       they both return the modified value too
    *)
    (* TODO:
       handle parens..
    *)
    ->
    let aux cxt f vid i =
      let cxt = vident cxt f vid in
      P.string f "[";
      P.string f (Int32.to_string  i);
      P.string f"]";
      cxt in
    (** TODO: parenthesize when necessary *)

    begin match delta, op with
      | {expression_desc = Number (Int { i =  1l; _})}, Plus
      | {expression_desc = Number (Int { i =  -1l; _})}, Minus
        ->
        P.string f L.plusplus;
        P.space f ;
        aux cxt f i k0
      | {expression_desc = Number (Int { i =  -1l; _})}, Plus
      | {expression_desc = Number (Int { i =  1l; _})}, Minus
        ->
        P.string f L.minusminus;
        P.space f ;
        aux cxt f  i k0
      | _, _ ->
        let cxt = aux cxt f i k0 in
        P.space f ;
        if op = Plus then P.string f "+="
        else P.string f "-=";
        P.space f ;
        expression 13 cxt  f delta
    end
  | Anything_to_string e ->
    (* Note that we should not apply any smart construtor here,
       it's purely  a convenice for pretty-printing
    *)
    expression_desc cxt l f (Bin (Plus, E.empty_string_literal , e))

  | Bin (Minus, {expression_desc = Number (Int {i=0l;_} | Float {f = "0."})}, e)
    (* TODO:
       Handle multiple cases like
       {[ 0. - x ]}
       {[ 0.00 - x ]}
       {[ 0.000 - x ]}
    *)
    ->
    let action () =
      P.string f "-" ;
      expression 13 cxt f e
    in
    if l > 13 then P.paren_group f 1 action
    else action ()

  | Bin (op, e1, e2) ->
    let (out, lft, rght) = op_prec op in
    let need_paren =
      l > out || (match op with Lsl | Lsr | Asr -> true | _ -> false) in

    let action () =
      (* We are more conservative here, to make the generated code more readable
          to the user
      *)

      let cxt = expression lft cxt  f e1 in
      P.space f;
      P.string f (op_str op);
      P.space f;
      expression rght cxt   f e2
    in
    if need_paren
    then P.paren_group f 1 action
    else action ()

  | String_append (e1, e2) ->
    let op : Js_op.binop = Plus in
    let (out, lft, rght) = op_prec op in
    let need_paren =
      l > out || (match op with Lsl | Lsr | Asr -> true | _ -> false) in

    let action () =
      let cxt = expression  lft cxt f e1 in
      P.space f ;
      P.string f "+";
      P.space f;
      expression rght  cxt   f e2
    in
    if need_paren then P.paren_group f 1 action else action ()

  | Array (el,_) ->
    (** TODO: simplify for singleton list *)
    begin match el with
      | []| [ _ ] -> P.bracket_group f 1 @@ fun _ -> array_element_list  cxt f el
      | _ -> P.bracket_vgroup f 1 @@ fun _ -> array_element_list  cxt f el
    end
  (* | Caml_uninitialized_obj (tag, size)
    ->  (* FIXME *)
    expression_desc cxt l f (Object [Length, size ; Tag, tag])     *)
  | Caml_block( el, mutable_flag, tag, tag_info)
    ->
    (* Note that, if we ignore more than tag [0] we loose some information
       with regard tag  *)
    begin match tag.expression_desc, tag_info with

      | Number (Int { i = 0l ; _})  ,
        (Blk_tuple | Blk_array | Blk_variant _ | Blk_record _ | Blk_na | Blk_module _
        |  Blk_constructor (_, 1) (* Sync up with {!Js_dump}*)
        )
        -> expression_desc cxt l f  (Array (el, mutable_flag))
      (* TODO: for numbers like 248, 255 we can reverse engineer to make it
         [Obj.xx_flag], but we can not do this in runtime libraries
      *)

      | _, _
        ->
        P.string f L.caml_block;
        P.string f L.dot ;
        P.string f L.caml_block_create;
        P.paren_group f 1
          (fun _ -> arguments cxt f [tag; E.array mutable_flag el])
    end
  | Caml_block_tag e ->
    P.group f 1 (fun _ ->
        let cxt = expression 15 cxt f  e in
        P.string f L.dot ;
        P.string f L.tag ;
        cxt)
  | Access (e, e')

  | String_access (e,e')
    ->
    let action () =
      P.group f 1 @@ fun _ ->
      let cxt = expression 15 cxt f e in
      P.bracket_group f 1 @@ fun _ ->
      expression 0 cxt f e'
    in
    if l > 15 then P.paren_group f 1 action else action ()

  | Length (e, _) ->
    let action () =  (** Todo: check parens *)
      let cxt = expression 15 cxt f e in
      P.string f L.dot;
      P.string f L.length;
      cxt  in
    if l > 15 then P.paren_group f 1 action else action ()

  | Dot (e, s,normal) ->
    let action () =
      let cxt = expression 15 cxt f e in
      Js_dump_property.property_access f s ;
      (* See [ .obj_of_exports]
         maybe in the ast level we should have
         refer and export
      *)
      cxt in
    if l > 15 then P.paren_group f 1 action else action ()

  | New (e,  el) ->
    let action () =
      P.group f 1 @@ fun _ ->
      P.string f L.new_;
      P.space f;
      let cxt = expression 16 cxt f e in
      P.paren_group f 1 @@ fun _ ->
      match el with
      | Some el  -> arguments cxt f el
      | None -> cxt
    in
    if l > 15 then P.paren_group f 1 action else action ()

  | Array_of_size e ->
    let action () =
      P.group f 1 @@ fun _ ->
      P.string f L.new_;
      P.space f;
      P.string f L.array;
      P.paren_group f 1 @@ fun _ -> expression 0 cxt f e
    in
    if l > 15 then P.paren_group f 1 action else action ()

  | Cond (e, e1, e2) ->
    let action () =
      (* P.group f 1 @@ fun _ ->  *)
      let cxt =  expression 3 cxt f e in
      P.space f;
      P.string f L.question;
      P.space f;
      (*
            [level 1] is correct, however
            to make nice indentation , force nested conditional to be parenthesized
          *)
      let cxt = (P.group f 1 @@ fun _ -> expression 3 cxt f e1) in
      (* let cxt = (P.group f 1 @@ fun _ -> expression 1 cxt f e1) in *)
      P.space f;
      P.string f L.colon;
      P.space f ;

      (* idem *)
      P.group f 1 @@ fun _ -> expression 3 cxt f e2
      (* P.group f 1 @@ fun _ -> expression 1 cxt f e2 *)
    in
    if l > 2 then P.paren_vgroup f 1 action else action ()

  | Object lst ->
    begin
      match lst with
      | [] -> P.string f "{ }" ; cxt
      | _ ->
        let action () =
          P.brace_vgroup f 1 @@ fun _ ->
          property_name_and_value_list cxt f lst in
        if l > 1 then
          (* #1946 object literal is easy to be
            interpreted as block statement
            here we avoid parens in such case
            {[
              var f = { x : 2 , y : 2}
            ]}
          *)
          P.paren_group f 1 action
        else action ()

    end

and property_name cxt f (s : J.property_name) : unit =
   Js_dump_property.property_key f s


and property_name_and_value_list cxt f l : Ext_pp_scope.t =
  match l with
  | [] -> cxt
  | [(pn, e)] ->
    property_name cxt  f pn ;
    P.string f L.colon;
    P.space f;
    expression 1 cxt f e
  | (pn, e) :: r ->
    property_name cxt f pn ;
    P.string f L.colon;
    P.space f;
    let cxt = expression 1 cxt f e in
    P.string f L.comma;
    P.newline f;
    property_name_and_value_list cxt f r

and array_element_list cxt f el : Ext_pp_scope.t =
  match el with
  | []     -> cxt
  | [e]    ->  expression 1 cxt f e
  | e :: r ->
    let cxt =  expression 1 cxt f e
    in
    P.string f L.comma; P.newline f; array_element_list cxt f r

and arguments cxt f l : Ext_pp_scope.t =
  match l with
  | []     -> cxt
  | [e]    ->   expression 1 cxt f e
  | e :: r ->
    let cxt =   expression 1 cxt f e in
    P.string f L.comma; P.space f; arguments cxt f r

and variable_declaration top cxt f
    (variable : J.variable_declaration) : Ext_pp_scope.t =
  (* TODO: print [const/var] for different backends  *)
  match variable with
  | {ident = i; value =  None; ident_info ; _} ->
    if ident_info.used_stats = Dead_pure
    then cxt
    else
      begin
        P.string f L.var;
        P.space f;
        let cxt = Ext_pp_scope.ident cxt  f i in
        semi f ;
        cxt
      end
  | { ident = name; value =  Some e; ident_info = {used_stats; _}} ->
    begin match used_stats with
      | Dead_pure ->
        cxt
      | Dead_non_pure ->
        (* Make sure parens are added correctly *)
        statement_desc top cxt f (J.Exp e)
      | _ ->
        begin match e, top  with
          | {expression_desc = Fun (method_, params, b, env ); comment = _}, _ ->
            pp_function method_ cxt f
              ~name:(if top then Name_top name else Name_non_top name)
              false params b env
          | _, _ ->
            P.string f L.var;
            P.space f;
            let cxt = Ext_pp_scope.ident cxt f name in
            P.space f ;
            P.string f L.eq;
            P.space f ;
            let cxt = expression 1 cxt f e in
            semi f;
            cxt
        end
    end
and ipp_comment : 'a . P.t -> 'a  -> unit = fun   f comment ->
  ()


(** don't print a new line -- ASI
    FIXME: this still does not work in some cases...
    {[
      return /* ... */
      [... ]
    ]}
*)

and pp_comment f comment =
  if String.length comment > 0 then
    begin
      P.string f "/* "; P.string f comment ; P.string f " */"
    end

and pp_comment_option f comment  =
  match comment with
  | None -> ()
  | Some x -> pp_comment f x
and statement top cxt f
    ({statement_desc = s;  comment ; _} : J.statement)  : Ext_pp_scope.t =

  pp_comment_option f comment ;
  statement_desc top cxt f s

and statement_desc top cxt f (s : J.statement_desc) : Ext_pp_scope.t =
  match s with
  | Block [] ->
    ipp_comment f  L.empty_block; (* debugging*)
    cxt
  | Exp {expression_desc = Var _;}
    -> (* Does it make sense to optimize here? *)
    semi f; cxt
  | Exp e ->
    (* Parentheses are required when the expression
       starts syntactically with "{" or "function"
       TODO:  be more conservative, since Google Closure will handle
       the precedence correctly, we also need people read the code..
       Here we force parens for some alien operators

       If we move assign into a statement, will be less?
       TODO: construct a test case that do need parenthesisze for expression
       IIE does not apply (will be inlined?)
    *)

    let rec need_paren  (e : J.expression) =
      match e.expression_desc with
      | Call ({expression_desc = Fun _; },_,_) -> true
      (* | Caml_uninitialized_obj _  *)
      | Raw_js_code (_, Exp)
      | Fun _ | Object _ -> true
      | Raw_js_code (_,Stmt)
      | Caml_block_set_tag _
      | Length _
      | Caml_block_set_length _
      | Anything_to_string _
      | String_of_small_int_array _
      | Call _
      | Array_append _
      | Array_copy _
      | Caml_block_tag _
      | Seq _
      | Dot _
      | Cond _
      | Bin _
      | Is_null_undefined_to_boolean _
      | String_access _
      | Access _
      | Array_of_size _
      | String_append _
      | Char_of_int _
      | Char_to_int _
      | Dump _
      | Json_stringify _
      | Math _
      | Var _
      | Str _
      | Unicode _
      | Array _
      | Caml_block  _
      | FlatCall _
      | Typeof _
      | Bind _
      | Number _
      | Caml_not _ (* FIXME*)
      | Js_not _
      | Bool _
      | New _
      | J.Anything_to_number _
        -> false
      (* e = function(x){...}(x);  is good
      *)
    in
    let cxt =
      (
        if need_paren  e
        then (P.paren_group f 1)
        else (P.group f 0)
      ) (fun _ -> expression 0 cxt f e ) in
    semi f;
    cxt

  | Block b -> (* No braces needed here *)
    ipp_comment f L.start_block;
    let cxt = statement_list top cxt  f b in
    ipp_comment f  L.end_block;
    cxt
  | Variable l ->
    variable_declaration top cxt  f l

  | If (e, s1,  s2) -> (* TODO: always brace those statements *)
    P.string f L.if_;
    P.space f;
    let cxt = P.paren_group f 1 @@ fun _ -> expression 0 cxt f e in
    P.space f;
    let cxt =
      block cxt f s1
    in
    begin match s2 with
      | None | (Some [])
      | Some [{statement_desc = (Block [] | Exp {expression_desc = Var _;} ); }]
        -> P.newline f; cxt
      | Some [{statement_desc = If _} as nest]
      | Some [{statement_desc = Block [ {statement_desc = If _ ; _} as nest] ; _}]
        ->
        P.space f;
        P.string f L.else_;
        P.space f;
        statement false cxt f nest
      | Some s2 ->
        P.space f;
        P.string f L.else_;
        P.space f ;
        block  cxt f s2
    end

  | While (label, e, s, _env) ->  (*  FIXME: print scope as well *)
    begin
      (match label with
       | Some i ->
         P.string f i ;
         P.string f L.colon;
         P.newline f ;
       | None -> ());
      let cxt =
        match e.expression_desc with
        | Number (Int {i = 1l}) ->
          P.string f L.while_;
          P.string f "(";
          P.string f L.true_;
          P.string f ")";
          P.space f ;
          cxt
        | _ ->
          P.string f L.while_;
          let cxt = P.paren_group f 1 @@ fun _ ->  expression 0 cxt f e in
          P.space f ;
          cxt
      in
      let cxt = block cxt f s in
      semi f;
      cxt
    end
  | ForRange (for_ident_expression, finish, id, direction, s, env) ->
    let action cxt  =
      P.vgroup f 0 @@ fun _ ->
      let cxt = P.group f 0 @@ fun _ ->
        (* The only place that [semi] may have semantics here *)
        P.string f "for";
        P.paren_group f 1 @@ fun _ ->
        let cxt, new_id =
          (match for_ident_expression, finish.expression_desc with
           | Some ident_expression , (Number _ | Var _ ) ->
             P.string f L.var;
             P.space f;
             let cxt  =  Ext_pp_scope.ident cxt f id in
             P.space f;
             P.string f L.eq;
             P.space f;
             expression 0 cxt f ident_expression, None
           | Some ident_expression, _ ->
             P.string f L.var;
             P.space f;
             let cxt  =  Ext_pp_scope.ident cxt f id in
             P.space f;
             P.string f L.eq;
             P.space f;
             let cxt = expression 1 cxt f ident_expression in
             P.space f ;
             P.string f L.comma;
             let id = Ext_ident.create (Ident.name id ^ "_finish") in
             let cxt = Ext_pp_scope.ident cxt f id in
             P.space f ;
             P.string f L.eq;
             P.space f;
             expression 1 cxt f finish, Some id
           | None, (Number _ | Var _) ->
             cxt, None
           | None , _ ->
             P.string f L.var;
             P.space f ;
             let id = Ext_ident.create (Ident.name id ^ "_finish") in
             let cxt = Ext_pp_scope.ident cxt f id in
             P.space f ;
             P.string f L.eq ;
             P.space f ;
             expression 15 cxt f finish, Some id
          ) in

        semi f ;
        P.space f;
        let cxt = Ext_pp_scope.ident cxt f id in
        P.space f;
        let right_prec  =

          match direction with
          | Upto ->
            let (_,_,right) = op_prec Le  in
            P.string f L.le;
            right
          | Downto ->
            let (_,_,right) = op_prec Ge in
            P.string f L.ge ;
            right
        in
        P.space f ;
        let cxt  =
          match new_id with
          | Some i -> expression   right_prec cxt  f (E.var i)
          | None -> expression  right_prec cxt  f finish
        in
        semi f;
        P.space f;
        let ()  =
          match direction with
          | Upto -> P.string f L.plus_plus
          | Downto -> P.string f L.minus_minus in
        Ext_pp_scope.ident cxt f id
      in
      block  cxt f s  in
    let lexical = Js_closure.get_lexical_scope env in
    if Ident_set.is_empty lexical
    then action cxt
    else
      (* unlike function,
         [print for loop] has side effect,
         we should take it out
      *)
      let inner_cxt = Ext_pp_scope.merge lexical cxt in
      let lexical = Ident_set.elements lexical in
      let _enclose action inner_cxt lexical   =
        let rec aux  cxt f ls  =
          match ls with
          | [] -> cxt
          | [x] -> Ext_pp_scope.ident cxt f x
          | y :: ys ->
            let cxt = Ext_pp_scope.ident cxt f y in
            P.string f L.comma;
            aux cxt f ys  in
        P.vgroup f 0
          (fun _ ->
             (
               P.string f "(function(";
               ignore @@ aux inner_cxt f lexical;
               P.string f ")";
               let cxt = P.brace_vgroup f 0  (fun _ -> action inner_cxt) in
               P.string f "(";
               ignore @@ aux inner_cxt f lexical;
               P.string f ")";
               P.string f ")";
               semi f;
               cxt
             ))
      in
      _enclose action inner_cxt lexical

  | Continue s ->
    P.string f L.continue;
    P.space f ;
    P.string f s;
    semi f;
    (* P.newline f; *)
    (* #2642 *)
    cxt
  | Debugger
    ->
    P.newline f ;
    P.string f L.debugger;
    semi f ;
    P.newline f;
    cxt
  | Break
    ->
    P.string f L.break;
    P.space f ;
    semi f;
    P.newline f;
    cxt

  | Return {return_value = e} ->
    begin match e with
      | {expression_desc = Fun (method_,  l, b, env); _} ->
        let cxt =
          pp_function method_ cxt f true l b env in
        semi f ; cxt
      | e ->
        P.string f L.return ;
        P.space f ;

        (* P.string f "return ";(\* ASI -- when there is a comment*\) *)
        P.group f return_indent @@ fun _ ->
        let cxt =  expression 0 cxt f e in
        semi f;
        cxt
        (* There MUST be a space between the return and its
           argument. A line return will not work *)
    end
  | Int_switch (e, cc, def) ->
    P.string f L.switch;
    P.space f;
    let cxt = P.paren_group f 1 @@ fun _ ->  expression 0 cxt f e
    in
    P.space f;
    P.brace_vgroup f 1 @@ fun _ ->
    let cxt = loop_case_clauses cxt f (fun f i -> P.string f (string_of_int i) ) cc in
    (match def with
     | None -> cxt
     | Some def ->
       P.group f 1 @@ fun _ ->
       P.string f L.default;
       P.string f L.colon;
       P.newline f;
       statement_list  false cxt  f def
    )

  | String_switch (e, cc, def) ->
    P.string f L.switch;
    P.space f;
    let cxt = P.paren_group f 1 @@ fun _ ->  expression 0 cxt f e
    in
    P.space f;
    P.brace_vgroup f 1 @@ fun _ ->
    let cxt = loop_case_clauses cxt f (fun f i -> Js_dump_string.pp_string f i ) cc in
    (match def with
     | None -> cxt
     | Some def ->
       P.group f 1 @@ fun _ ->
       P.string f L.default;
       P.string f L.colon;
       P.newline f;
       statement_list  false cxt  f def )

  | Throw e ->
    P.string f L.throw;
    P.space f ;
    P.group f throw_indent @@ fun _ ->

    let cxt = expression 0 cxt f e in
    semi f ; cxt

  (* There must be a space between the return and its
     argument. A line return would not work *)
  | Try (b, ctch, fin) ->
    P.vgroup f 0 @@ fun _->
    P.string f "try";
    P.space f ;
    let cxt = block cxt f b in
    let cxt =
      match ctch with
      | None ->
        cxt
      | Some (i, b) ->
        P.newline f;
        P.string f "catch (";
        let cxt = Ext_pp_scope.ident cxt f i in
        P.string f ")";
        block cxt f b
    in
    begin match fin with
      | None -> cxt
      | Some b ->
        P.group f 1 @@ fun _ ->
        P.string f "finally";
        P.space f;
        block cxt f b
    end
(* similar to [block] but no braces *)
and statement_list top cxt f  b =
  match b with
  | []     -> cxt
  | [s]    -> statement top  cxt f  s
  | s :: r ->
    let cxt = statement top cxt f s in
    P.newline f;
    (if top then P.force_newline f);
    statement_list top cxt f  r

and block cxt f b =
  (* This one is for '{' *)
  P.brace_vgroup f 1 (fun _ -> statement_list false cxt   f b )




(* let program f cxt   ( x : J.program ) =
  let () = P.force_newline f in
  let cxt =  statement_list true cxt f x.block  in
  let () = P.force_newline f in
  Js_dump_import_export.exports cxt f x.exports *)

(* let dump_program (x : J.program) oc =
  ignore (program (P.from_channel oc)  Ext_pp_scope.empty  x ) *)

let string_of_block  block
  =
  let buffer  = Buffer.create 50 in
  begin
    let f = P.from_buffer buffer in
    let _scope =  statement_list true Ext_pp_scope.empty  f block in
    P.flush  f ();
    Buffer.contents buffer
  end


let string_of_expression e =
  let buffer  = Buffer.create 50 in
  begin
    let f = P.from_buffer buffer in
    let _scope =  expression 0  Ext_pp_scope.empty  f e in
    P.flush  f ();
    Buffer.contents buffer
  end