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  *)

[@@@ocaml.warning "-57"] (* FIXME: turn off such warning temporarily*)

(*
  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
     ====================
   ]}

*)

let name_symbol = Js_op.Symbol_name
module P = Ext_pp
module E = Js_exp_make
(* module S = Js_stmt_make *)

module L = Js_dump_lit

(* There modules are dynamically inserted in the last stage
  {Caml_curry}
  {Caml_option}

  They can appear anywhere so even if you have a module 
  {
    let module Caml_block = ...

    (* Later would insert the use of Caml_block here which should 
      point tto the runtime module
    *)
  }
  There are no sane way to easy detect it ahead of time, we should be
  conservative here.
  (our call Js_fun_env.get_unbounded env) is not precise
*)


module Curry_gen = struct 
  let pp_curry_dot f =   
    P.string f Js_runtime_modules.curry;
    P.string f L.dot 
  let pp_optimize_curry (f : P.t) (len : int) = 
    pp_curry_dot f;
    P.string f "__";
    P.string f (Printf.sprintf "%d" len)

  let pp_app_any (f : P.t) =    
    pp_curry_dot f;
    P.string f "app"

  let pp_app (f : P.t) (len : int) =    
    pp_curry_dot f;
    P.string f "_"; 
    P.string f (Printf.sprintf "%d" len)
end 



let return_indent = String.length L.return / Ext_pp.indent_length

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

type cxt = Ext_pp_scope.t

let semi f = P.string f L.semi
let comma f = P.string f L.comma

let exn_block_as_obj 
    ~(stack : bool) 
    (el : J.expression list) 
    (ext : J.tag_info) : J.expression_desc =
  let field_name  = 
    match ext with 
    | Blk_extension -> (fun i -> 
        match i with 
        | 0 ->  Literals.exception_id
        | i ->  
          "_" ^ string_of_int i
      )
    | Blk_record_ext ss ->   
      (fun i ->  
         match i with 
         | 0 -> Literals.exception_id
         | i ->   ss.(i-1))
    | _ -> assert false in   
  Object (
    if stack then   
      Ext_list.mapi_append el (fun i e -> Js_op.Lit (field_name i), e)
        [ Js_op.Lit "Error", 
         E.new_ (E.js_global "Error") []
        ]
    else Ext_list.mapi  el (fun i e -> Js_op.Lit (field_name i), e)
  )

let rec iter_lst cxt (f : P.t) ls element inter = 
  match ls with 
  | [] -> cxt 
  | [e] -> element cxt f e 
  | e::r -> 
    let acxt = element cxt f e  in 
    inter f; 
    iter_lst acxt f r element inter

let raw_snippet_exp_simple_enough (s : string) =
  Ext_string.for_all s (fun c -> 
  match c with 
  | 'a' .. 'z' | 'A' .. 'Z' | '_' | '.' -> true 
  | _ -> false
  )
(* 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?)
*)

(* e = function(x){...}(x);  is good
*)        
let exp_need_paren  (e : J.expression) =
  match e.expression_desc with
  (* | Caml_uninitialized_obj _  *)
  | Call ({expression_desc = Fun _  | Raw_js_code _ },_,_) -> true

  | Raw_js_code {code_info = Exp _}
  | Fun _ 
  | Caml_block (_,_,_, (Blk_record _ | Blk_module _))
  | Object _ -> true
  | Raw_js_code {code_info = Stmt _ }
  | Length _
  | Call _
  | Caml_block_tag _
  | Seq _
  | Static_index _
  | Cond _
  | Bin _
  | Is_null_or_undefined _
  | String_index _
  | Array_index _
  | String_append _
  | Char_of_int _
  | Char_to_int _
  | Var _
  | Undefined
  | Null
  | Str _
  | Unicode _
  | Array _
  | Optional_block _
  | Caml_block  _
  | FlatCall _
  | Typeof _
  | Number _
  | Js_not _
  | Bool _
  | New _
    -> false



let comma_idents (cxt: cxt) f ls =     
  iter_lst cxt f ls   
  Ext_pp_scope.ident
  comma

let pp_paren_params 
    (inner_cxt : cxt) (f : Ext_pp.t) 
    (lexical : Ident.t list) : unit =   
  P.string f L.lparen;
  let _ : cxt =  comma_idents inner_cxt f lexical in 
  P.string f L.rparen

(** Print as underscore for unused vars, may not be 
    needed in the future *)  
(* let ipp_ident cxt f id (un_used : bool) =
  Ext_pp_scope.ident cxt f (
    if un_used then
      Ext_ident.make_unused () 
    else
      id) *)

let pp_var_assign cxt f id  =       
  P.string f L.var ; 
  P.space f ; 
  let acxt = Ext_pp_scope.ident cxt f id in 
  P.space f ; 
  P.string f L.eq ; 
  P.space f ;
  acxt 


let pp_var_assign_this cxt f id =   
  let cxt = pp_var_assign cxt f id in 
  P.string f L.this;
  P.space f ;
  semi f ;
  P.newline f ;
  cxt 

let pp_var_declare cxt f id = 
  P.string f L.var ; 
  P.space f ; 
  let acxt = Ext_pp_scope.ident cxt f id in 
  semi f ;
  acxt 

let pp_direction f (direction : J.for_direction) =   
  match direction with
  | Up
  | Upto -> P.string f L.plus_plus
  | Downto -> P.string f L.minus_minus 

let return_sp f = 
    P.string f L.return ; P.space f   

let bool f b =     
  P.string f (if b then  L.true_ else L.false_)

let comma_sp f =   
  comma f ; P.space f 
let comma_nl f = 
  comma f ; P.newline f 

(* let drop_comment (x : J.expression) = 
  if x.comment = None then x 
  else {x with comment = None}   *)

let debugger_nl f =   
  P.newline f ; 
  P.string f L.debugger;
  semi f ;
  P.newline f 

let break_nl f =   
  P.string f L.break;
  P.space f ;
  semi f;
  P.newline f

let continue f s =   
  P.string f L.continue;
  P.space f ;
  P.string f s;
  semi f


let formal_parameter_list cxt f  l   = 
    iter_lst cxt f l Ext_pp_scope.ident comma_sp 
(* 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
*)


(**
   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
*)

let is_var (b : J.expression)  a = 
  match b.expression_desc with 
  | Var (Id i) -> Ident.same i a 
  | _ -> false

type fn_exp_state = 
  | Is_return (* for sure no name *)
  | Name_top of Ident.t
  | Name_non_top of Ident.t
  | No_name of {single_arg : bool} (* true means for sure, false -- not sure *)

let default_fn_exp_state = No_name {single_arg = false}  

(* 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 =
  Curry_gen.pp_optimize_curry f len ; 
  P.paren_group f 1 (fun _ -> expression ~level:1 cxt f function_id  )


and  pp_function ~is_method
    cxt (f : P.t) ~fn_state
    (l : Ident.t list) (b : J.block) (env : Js_fun_env.t ) : cxt =
  match b  with
  | [ {statement_desc =
         Return 
                   {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 )})}}]
    when
      (* match such case:
         {[ function(x,y){ return u(x,y) } ]}
         it can be optimized in to either [u] or [Curry.__n(u)]
      *)
      not is_method &&
      Ext_list.for_all2_no_exn ls l  is_var  ->
    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 *)
    (match fn_state with
     | Name_top i | Name_non_top i  ->       
       let cxt = pp_var_assign cxt f i in 
       let cxt = optimize len ~p:(arity = NA && len <= 8) cxt f v in
       semi f ;
       cxt
     | Is_return  
     | No_name _ ->
       if fn_state = Is_return then 
         return_sp f ;
       optimize len ~p:(arity = NA && len <=8) cxt f v)

  | _  ->
    let set_env : Set_ident.t = (** identifiers will be printed following*)
      match fn_state with
      | Is_return
      | No_name _ ->
        Js_fun_env.get_unbounded env
      | Name_top id | Name_non_top id -> 
        Set_ident.add (Js_fun_env.get_unbounded env ) id in
    (* the context will be continued after this function *)
    let outer_cxt = Ext_pp_scope.merge cxt set_env 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
    let param_body () : unit =
      if is_method then
        match l with 
        | [] -> assert false 
        | this::arguments -> 
          let cxt = P.paren_group f 1 (fun _ ->
              formal_parameter_list inner_cxt  f  arguments )
          in
          P.space f ;
          P.brace_vgroup f 1 (fun _ ->
              let cxt =
                if Js_fun_env.get_unused env 0 then cxt 
                else  pp_var_assign_this cxt f this in
              function_body cxt f b
            );
      else 
        let cxt = 
          P.paren_group f 1 (fun _ -> formal_parameter_list inner_cxt  f  l  ) in
        P.space f ;
        P.brace_vgroup f 1 (fun _ -> function_body cxt f b ) 
    in
    let lexical : Set_ident.t = Js_fun_env.get_lexical_scope env in
    let enclose  lexical  =
      let handle lexical =
        if  Set_ident.is_empty lexical
        then
          (
           match fn_state with
           | Is_return -> 
             return_sp f ;
             P.string f L.function_;
             P.space f ;
             param_body ()                
           | No_name {single_arg } ->
             (* see # 1692, add a paren for annoymous function for safety  *)
             P.cond_paren_group f (not single_arg) 1  (fun _ ->
                 P.string f L.function_;
                 P.space f ;
                 param_body ())                
           | Name_non_top x  ->
             ignore (pp_var_assign inner_cxt f x : cxt ); 
             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 : cxt);
             param_body ())
        else
          (* print our closure as
             {[(function(x,y){ return function(..){...}} (x,y))]}
             Maybe changed to `let` in the future
          *)
          let lexical = Set_ident.elements lexical in
          (
             match fn_state with
             | Is_return -> return_sp f 
             | No_name _ -> ()
             | Name_non_top name | Name_top name->
               ignore (pp_var_assign inner_cxt f name : cxt)
          )
          ;
          P.string f L.lparen;
          P.string f L.function_;
          pp_paren_params inner_cxt f lexical; 
          P.brace_vgroup f 0  (fun _ ->
              return_sp f;
              P.string f L.function_;
              P.space f ;
              (match fn_state with
               | Is_return
               | No_name _ -> ()
               | Name_non_top x | Name_top x -> ignore (Ext_pp_scope.ident inner_cxt f x));
              param_body ());
          pp_paren_params inner_cxt f lexical;     
          P.string f L.rparen;
          match fn_state with
          | Is_return
          | No_name _ -> () (* expression *)
          | _ -> semi f (* has binding, a statement *)  in
      handle 
        (match fn_state with
         | Name_top name | Name_non_top name  when Set_ident.mem lexical name ->
           (*TODO: when calculating lexical we should not include itself *)
           Set_ident.remove lexical name
         | _ -> lexical) in
    enclose lexical;
    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_body ; should_break; comment; } : _ J.case_clause) ->
    let cxt =
      P.group f 1  (fun _ ->
          P.group f 1 (fun _ ->
              P.string f L.case;
              P.space f ;
              pp_comment_option f comment;
              pp_cond  f switch_case; (* could be integer or string *)
              P.space f ;
              P.string f L.colon  );
          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 . cxt ->
  P.t -> (P.t -> 'a -> unit) -> 'a J.case_clause list -> cxt
  = fun  cxt  f pp_cond cases ->
    Ext_list.fold_left cases cxt (fun acc x -> pp_one_case_clause acc f pp_cond x)              

and vident cxt f  (v : J.vident) =
  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

(* The higher the level, the more likely that inner has to add parens *)
and expression ~level:l cxt  f (exp : J.expression) : cxt =
  pp_comment_option f exp.comment ;
  expression_desc cxt ~level:l f exp.expression_desc

and expression_desc cxt ~(level:int) f x : cxt  =
  match x with
  | Null ->
    P.string f L.null; cxt 
  | Undefined -> 
    P.string f L.undefined; cxt 
  | Var v ->
    vident cxt f v
  | Bool b ->
    bool f b ; cxt
  | Seq (e1, e2) ->
    P.cond_paren_group f (level > 0) 1 (fun () ->
      let cxt = expression ~level:0 cxt f e1 in
      comma_sp f;
      expression ~level:0 cxt f e2 )
  | Fun (is_method, l, b, env) ->  (* TODO: dump for comments *)
    pp_function ~is_method cxt f ~fn_state:default_fn_exp_state  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) ->
    P.cond_paren_group f (level > 15) 1  (fun _ -> 
      P.group f 1 (fun _ ->
          match info, el  with
          | {arity  = Full }, _
          | _, [] ->
            let cxt = expression ~level:15 cxt f e in
            P.paren_group f 1 (fun _ -> 
                match el with 
                | [{expression_desc = Fun (is_method, l,b,env)}]
                  -> 
                  pp_function ~is_method cxt f ~fn_state:(No_name {single_arg = true})
                    l b env 
                | _ ->       
                  arguments cxt  f el
              )

          | _ , _ ->
            let len = List.length el in
            if 1 <= len && len <= 8 then
              begin
                Curry_gen.pp_app f len ; 
                P.paren_group f 1 (fun _ -> arguments cxt f (e::el))
              end
            else
              begin
                Curry_gen.pp_app_any f ;
                P.paren_group f 1
                  (fun _ -> arguments cxt f [ e ; E.array Mutable el])
              end))
  | FlatCall(e,el) ->
    P.group f 1 (fun _ ->
        let cxt = expression ~level: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;
            comma_sp f ;
            expression ~level:1 cxt f el
          )
      )
  | Char_to_int e ->
    (match e.expression_desc with
     | String_index (a,b) ->
       P.group f 1 (fun _ ->
           let cxt = expression ~level:15 cxt f a in
           P.string f L.dot;
           P.string f L.char_code_at;
           P.paren_group f 1 (fun _ -> expression ~level:0 cxt f b);
         )
     | _ ->
       P.group f 1 (fun _ ->
           let cxt = expression ~level:15 cxt f e in
           P.string f L.dot;
           P.string f L.char_code_at;
           P.string f "(0)";
           cxt))
  | 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])
      )  
  | 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 {code = s; code_info = info} ->
    (match info with
     | Exp exp_info ->
       let raw_paren =
          not (match exp_info with  
            | Js_literal _ | Js_raw_json -> true 
            | Js_function _ | Js_exp_unknown -> false || raw_snippet_exp_simple_enough s) in 
       if raw_paren then P.string f L.lparen;
       P.string f s ;       
       if raw_paren then  P.string f L.rparen;
       cxt
     | Stmt stmt_info ->
       if stmt_info = Js_stmt_comment then P.string f s 
       else begin P.newline f  ;
       P.string f s ;
       P.newline f end ;
       cxt)
  
  | Number v ->
    let s =
      match v with
      | Float {f} ->
        Js_number.caml_float_literal_to_js_string f
      (* attach string here for float constant folding?*)
      | Int { i; _}
        -> Int32.to_string i (* 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 level > 13  (* Negative numbers may need to be parenthesized. *)
      else level = 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
  | Is_null_or_undefined e ->
    P.cond_paren_group f (level > 0) 1 (fun _ ->
        let cxt = expression ~level:1 cxt f e in
        P.space f ;
        P.string f "==";
        P.space f ;
        P.string f L.null;
        cxt)  
  | Js_not e ->
    P.cond_paren_group f (level > 13) 1 (fun _ -> 
      P.string f "!" ;
      expression ~level:13 cxt f e
    )
  | Typeof e
    ->
    P.string f "typeof";
    P.space f;
    expression ~level:13 cxt f e
 
  | Bin (Eq, ({expression_desc = Array_index({expression_desc = Var i; _},
                                       {expression_desc = Number (Int {i = k0 })}
                                      ) } as lhs),
         {expression_desc =
            (Bin((Plus as op),
                 {expression_desc = Array_index(
                      {expression_desc = Var j; _},
                      {expression_desc = Number (Int {i = k1; })}
                    ); _}, delta)
            | Bin((Plus as op), delta,
                  {expression_desc = Array_index(
                       {expression_desc = Var j; _},
                       {expression_desc = Number (Int {i = k1; })}
                     ); _})
            | Bin((Minus as op),
                  {expression_desc = Array_index(
                       {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..
    *)
    ->
    (** TODO: parenthesize when necessary *)
    (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 ;
       expression ~level:13 cxt f lhs (* Static index level is 15*)
     | {expression_desc = Number (Int { i =  -1l; _})}, Plus
     | {expression_desc = Number (Int { i =  1l; _})}, Minus
       ->
       P.string f L.minusminus;
       P.space f ;
       expression ~level:13 cxt f lhs
       
     | _, _ ->
       let cxt = expression ~level:13 cxt f lhs in
       P.space f ;
       P.string f (if op = Plus then "+=" else "-=");
       P.space f ;
       expression ~level:13 cxt  f delta) 


  | 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 ]}
    *)
    ->
    P.cond_paren_group f (level > 13 ) 1 (fun _ -> 
      P.string f "-" ;
      expression ~level:13 cxt f e
    )
  | Bin (op, e1, e2) ->
    let (out, lft, rght) = Js_op_util.op_prec op in
    let need_paren =
      level > out || (match op with Lsl | Lsr | Asr -> true | _ -> false) in
    (* We are more conservative here, to make the generated code more readable
          to the user *)
    P.cond_paren_group f need_paren 1  (fun _ -> 
      let cxt = expression ~level:lft cxt  f e1 in
      P.space f;
      P.string f (Js_op_util.op_str op);
      P.space f;
      expression ~level:rght cxt   f e2)
  | String_append (e1, e2) ->
    let op : Js_op.binop = Plus in
    let (out, lft, rght) = Js_op_util.op_prec op in
    let need_paren =
      level > out || (match op with Lsl | Lsr | Asr -> true | _ -> false) in
    P.cond_paren_group f need_paren 1 (fun _ -> 
      let cxt = expression  ~level:lft cxt f e1 in
      P.space f ;
      P.string f "+";
      P.space f;
      expression  ~level:rght cxt   f e2)
  | Array (el,_) ->
    (** TODO: simplify for singleton list *)
      (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))
  | Optional_block (e,identity) -> 
    expression ~level cxt f  
      (if identity then e 
       else       
         E.runtime_call Js_runtime_modules.option "some" [e])
  | Caml_block(el,_, _, Blk_module fields) ->        
      expression_desc cxt ~level f (Object (
        (Ext_list.map_combine 
          fields el 
          (fun  x -> Js_op.Lit (Ext_ident.convert x) ))))
  (*name convention of Record is slight different from modules*)        
  | Caml_block(el,mutable_flag, _, Blk_record fields) ->  
    if Ext_array.for_alli fields (fun i v -> string_of_int i = v) then 
      expression_desc cxt ~level f  (Array (el, mutable_flag))
    else      
      expression_desc cxt ~level f (Object 
        ((Ext_list.combine_array fields el  (fun i -> Js_op.Lit i))))      
        
  | Caml_block(el,_,_, Blk_poly_var name) ->
    begin match el with 
      | [hash;value] -> 
        expression_desc 
          cxt 
          ~level 
          f 
          (Object 
             ((Js_op.Lit Literals.polyvar_hash, 
               if !Js_config.debug then hash
               else {hash with comment = Some name}
              ) ::
              (Js_op.Lit Literals.polyvar_value, value) ::
              if !Js_config.debug then 
                [name_symbol, E.str name]
              else []
             )          
          )
      | _ -> assert false
    end       
  | Caml_block(el,_, _, (Blk_extension | Blk_record_ext _ as ext )) ->             
    expression_desc cxt ~level f (exn_block_as_obj ~stack:false el ext)
  | Caml_block(el,_,tag, (Blk_record_inlined p)) -> 
    let objs = 
      let tails =   
        Ext_list.combine_array_append p.fields el      
          (if !Js_config.debug then [name_symbol,E.str p.name]
           else []
          ) (fun i -> Js_op.Lit i) in 
      if p.num_nonconst = 1 then tails
      else (Js_op.Lit L.tag,
        if !Js_config.debug then tag else {tag with comment = Some p.name}) :: tails in 
    if p.num_nonconst = 1 && not !Js_config.debug then 
      pp_comment_option f (Some p.name);
    expression_desc cxt ~level f (Object objs)  
  | Caml_block(el,_,tag, (Blk_constructor p)) -> 
    let is_cons = p.name = Literals.cons in   
    let objs =     
      let tails =   
        Ext_list.mapi_append el (fun i e -> 
          (match is_cons, i with 
          | true,  0 -> Js_op.Lit Literals.hd
          | true,  1 -> Js_op.Lit Literals.tl 
          | _ ->
          Js_op.Lit ("_" ^ string_of_int i)) , e )
          (if !Js_config.debug then 
             [name_symbol, E.str p.name]
           else []) in         
      if p.num_nonconst = 1 then       
        tails
      else         
        (Js_op.Lit L.tag,
          if !Js_config.debug then tag else {tag with comment = Some p.name}) :: tails
    in 
    if p.num_nonconst = 1 && not !Js_config.debug 
      && not is_cons then 
      pp_comment_option f (Some p.name);
    expression_desc cxt ~level f (Object objs)
  | Caml_block ( _, _, _, (Blk_module_export | Blk_na _ )) -> assert false
  | Caml_block( el, mutable_flag, _tag, (Blk_tuple  | Blk_class | Blk_array  ))
    ->
    expression_desc cxt ~level f  (Array (el, mutable_flag))
 
  | Caml_block_tag e ->
    P.group f 1 (fun _ ->
        let cxt = expression ~level:15 cxt f  e in
        P.string f L.dot ;
        P.string f L.tag ;
        cxt)
  | Array_index (e, p)
  | String_index (e,p)
    ->
    P.cond_paren_group f (level > 15) 1 (fun _ -> 
        P.group f 1  (fun _ ->
        let cxt = expression ~level:15 cxt f e in
        P.bracket_group f 1 (fun _ ->
        expression ~level:0 cxt f p )))  
  | Static_index (e, s,_) ->
    P.cond_paren_group f (level > 15) 1 (fun _ -> 
        let cxt = expression ~level: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) 

  | Length (e, _) ->
    (** Todo: check parens *)
    P.cond_paren_group f (level > 15) 1 (fun _ -> 
      let cxt = expression ~level:15 cxt f e in
      P.string f L.dot;
      P.string f L.length;
      cxt)
  | New (e,  el) ->
    P.cond_paren_group f (level > 15) 1 (fun _ ->
        P.group f 1 ( fun _ ->
            P.string f L.new_;
            P.space f;
            let cxt = expression ~level:16 cxt f e in
            P.paren_group f 1 (fun _ ->
                match el with
                | Some el  -> arguments cxt f el
                | None -> cxt)))
  | Cond (e, e1, e2) ->
    let action () =      
      let cxt =  expression ~level: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 ~level:3 cxt f e1) in

      P.space f;
      P.string f L.colon;
      P.space f ;
      (* idem *)
      P.group f 1 (fun _ -> expression ~level:3 cxt f e2)
    in
    if level > 2 then P.paren_vgroup f 1 action else action ()

  | Object lst ->    
    let action () =
      if lst = [] then begin P.string f "{}" ; cxt end else      
        P.brace_vgroup f 1 (fun _ ->
            property_name_and_value_list cxt f lst) in
    if level > 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 ()

and property_name_and_value_list cxt f (l : J.property_map) =     
  iter_lst cxt f l (fun cxt f (pn,e) -> 
    Js_dump_property.property_key f pn ;
    P.string f L.colon;
    P.space f;
    expression ~level:1 cxt f e
  ) comma_nl      

and array_element_list cxt f (el : E.t list) : cxt =
  iter_lst cxt f el (expression ~level:1) comma_nl
 
and arguments cxt f (l : E.t list) : cxt =
  iter_lst cxt f l (expression ~level:1) comma_sp
  
and variable_declaration top cxt f
    (variable : J.variable_declaration) : cxt =
  (* 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 pp_var_declare cxt f i 
  | { ident = name; value =  Some e; ident_info = {used_stats; _}} ->
    match used_stats with
    | Dead_pure ->
      cxt
    | Dead_non_pure ->
      (* Make sure parens are added correctly *)
      statement_desc top cxt f (J.Exp e)
    | _ ->
      match e.expression_desc  with
      | Fun (is_method, params, b, env ) ->
        pp_function ~is_method cxt f
          ~fn_state:(if top then Name_top name else Name_non_top name)
          params b env      
      | _ ->
        let cxt = pp_var_assign cxt f name in 
        let cxt = expression ~level:1 cxt f e in
        semi f;
        cxt

    
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)  : cxt =

  pp_comment_option f comment ;
  statement_desc top cxt f s

and statement_desc top cxt f (s : J.statement_desc) : cxt =
  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 ->
    (
      match e.expression_desc with 
      | Raw_js_code {code ; code_info =  Stmt (Js_stmt_comment)} -> 
        P.string f code;
        cxt
      | Raw_js_code {code_info =  Exp (Js_literal {comment})} -> 
        (match comment with (* The %raw is just a comment *)
        | Some s ->
          P.string f s;
        | None -> ());
        cxt

      | _ ->  
        let cxt =
          (
            if exp_need_paren  e
            then P.paren_group f 1
            else P.group f 0
          ) (fun _ -> expression ~level: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 ~level:0 cxt f e) in
    P.space f;
    let cxt = block cxt f s1 in
    (match s2 with
     | []
     | [{statement_desc = (Block [] | Exp {expression_desc = Var _;} ); }]
       -> P.newline f; cxt
     | [{statement_desc = If _} as nest]
     | [{statement_desc = Block [ {statement_desc = If _ ; _} as nest] ; _}]
       ->
       P.space f;
       P.string f L.else_;
       P.space f;
       statement false cxt f nest
     | (_::_) as s2 ->
       P.space f;
       P.string f L.else_;
       P.space f ;
       block  cxt f s2)
  | 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 L.lparen;
          P.string f L.true_;
          P.string f L.rparen;
          P.space f ;
          cxt
        | _ ->
          P.string f L.while_;
          let cxt = P.paren_group f 1 (fun _ ->  expression ~level: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 L.for_ ;
              P.paren_group f 1 ( fun _ ->
                  let cxt, new_id =
                    match for_ident_expression, finish.expression_desc with
                    | Some ident_expression , (Number _ | Var _ ) ->
                      let cxt = pp_var_assign cxt f id in  
                      expression ~level:0 cxt f ident_expression, None
                    | Some ident_expression, _ ->
                      let cxt = pp_var_assign cxt f id in 
                      let cxt = expression ~level:1 cxt f ident_expression in
                      P.space f ;
                      comma 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 ~level:1 cxt f finish, Some id
                    | None, (Number _ | Var _) ->
                      cxt, None
                    | None , _ ->
                      let id = Ext_ident.create (Ident.name id ^ "_finish") in
                      let cxt = pp_var_assign cxt f id in 
                      expression ~level: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) = Js_op_util.op_prec Le  in
                      P.string f L.le;
                      right
                    | Up ->  
                      let (_,_,right) = Js_op_util.op_prec Lt  in
                      P.string f L.lt;
                      right
                    | Downto ->
                      let (_,_,right) = Js_op_util.op_prec Ge in
                      P.string f L.ge ;
                      right
                  in
                  P.space f ;
                  let cxt  =
                    expression   ~level:right_prec cxt  f 
                      (match new_id with
                       | Some i -> E.var i
                       | None -> finish) in
                  semi f;
                  P.space f;
                  pp_direction f direction;
                  Ext_pp_scope.ident cxt f id)) in
          block  cxt f s ) in
    let lexical = Js_closure.get_lexical_scope env in
    if Set_ident.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 cxt lexical in
      let lexical = Set_ident.elements lexical in
      P.vgroup f 0
        (fun _ ->
           P.string f L.lparen;
           P.string f L.function_;               
           pp_paren_params inner_cxt f lexical; 
           let cxt = P.brace_vgroup f 0  (fun _ -> action inner_cxt) in               
           pp_paren_params inner_cxt f lexical; 
           P.string f L.rparen;
           semi f;
           cxt
        )
  | Continue s -> continue f s ; cxt
    (* P.newline f;  #2642 *)    
  | Debugger ->  debugger_nl f ; cxt
  | Break -> break_nl f; cxt

  | Return e ->
    begin match e.expression_desc with
      | Fun (is_method,  l, b, env) ->
        let cxt =
          pp_function ~is_method cxt f ~fn_state:Is_return l b env in
        semi f ; cxt
      | Undefined ->  
        return_sp f;
        semi f;
        cxt 
      | _ ->
        return_sp f ;
        (* P.string f "return ";(\* ASI -- when there is a comment*\) *)
        P.group f return_indent (fun _ ->
            let cxt =  expression ~level: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 ~level: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 ~level:0 cxt f e) in
    P.space f;
    P.brace_vgroup f 1 (fun _ ->
        let cxt = loop_case_clauses cxt f Js_dump_string.pp_string  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 ->
    let e = match e.expression_desc with 
      | Caml_block (el,_,_,(Blk_extension | Blk_record_ext _ as ext)) -> 
        {e with expression_desc = exn_block_as_obj ~stack:true el ext} 
      | _ -> e in 
    P.string f L.throw;
    P.space f ;
    P.group f throw_indent  (fun _ ->
        let cxt = expression ~level: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 L.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
        match fin with
        | None -> cxt
        | Some b ->
          P.group f 1 (fun _ ->
              P.string f L.finally;
              P.space f;
              block cxt f b))

and function_body (cxt : cxt) f (b : J.block) : unit =
  match b with
  | []     -> ()
  | [s]    ->
    begin match s.statement_desc with
    | If (bool,
          then_,
           [{
              statement_desc =
                Return {expression_desc = Undefined}} ])
        ->
        ignore (statement false cxt f {s with statement_desc = If(bool,then_, [])} : cxt)
    | Return {expression_desc = Undefined } -> ()    
    | _ ->        
      ignore (statement false  cxt f  s : cxt)
    end
  | s :: r ->
    let cxt = statement false cxt f s in
    P.newline f;
    function_body cxt f  r

(* similar to [block] but no braces *)
and statement_list top cxt f  b =
  iter_lst cxt f b  (fun cxt f s -> statement top cxt f s )
    (if top then 
      (fun f -> P.newline f ; P.force_newline f )
      else P.newline
    )


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




let string_of_block  (block : J.block) =
  let buffer  = Buffer.create 50 in
  let f = P.from_buffer buffer in
  let _ : cxt =  statement_list true Ext_pp_scope.empty  f block in
  P.flush  f ();
  Buffer.contents buffer



let string_of_expression (e : J.expression) =
  let buffer  = Buffer.create 50 in
  let f = P.from_buffer buffer in
  let _ : cxt =  expression ~level:0  Ext_pp_scope.empty  f e in
  P.flush  f ();
  Buffer.contents buffer