Source file resolve_python.ml

(* Yoann Padioleau
 *
 * Copyright (C) 2019 r2c
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * version 2.1 as published by the Free Software Foundation, with the
 * special exception on linking described in file license.txt.
 * 
 * This library 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 file
 * license.txt for more details.
 *)
open Ast_python
module Ast = Ast_python
module V = Visitor_python

(*****************************************************************************)
(* Prelude *)
(*****************************************************************************)
(* Identifiers tagger (so we can colorize them differently in codemap/efuns).
 *
 * See also Ast_python.resolved_name.
 *
 * TODO: generalize for ast_generic at some point?
 * This naming phase helps dealing with:
 *  - scoping issues in static analysis as it deals with
      * variable shadowing (every variables now have a different name)
 *  - coloring identifiers in codemap/efuns
 *)

(*****************************************************************************)
(* Type *)
(*****************************************************************************)
type context = 
  | AtToplevel
  | InClass
  | InFunction
  (* TODO: InLambda *)
 
type env = {
  ctx: context ref;
  names: (string * resolved_name) list ref;
}

let default_env () = {
  ctx = ref AtToplevel;
  names = ref [];
}

(*****************************************************************************)
(* Helpers *)
(*****************************************************************************)

(* because we use Visitor_python instead of a clean recursive 
 * function passing down an environment, we need to emulate a scoped
 * environment by using save_excursion.
 *)
let with_added_env xs env f = 
  let newnames = xs @ !(env.names) in
  Common.save_excursion env.names newnames f

let add_name_env name kind env =
  env.names := (Ast.str_of_name name, kind)::!(env.names)

let with_new_context ctx env f = 
  Common.save_excursion env.ctx ctx f


let params_of_parameters params =
  params |> Common.map_filter (function
    | ParamClassic ((name, _), _)
    | ParamStar (name, _) | ParamPow (name, _) 
    -> Some name
   )

(*****************************************************************************)
(* Entry point *)
(*****************************************************************************)

let resolve prog =
  let env = default_env () in

  (* helper to factorize code related to (polymorphic comprehension) *)
  let comprehension ke v (e, xs) =
    let new_vars = 
      xs |> Common.map_filter (function
        | CompFor (target, _) -> 
            (match target with
            | Name (name, _ctx, _res) -> Some name
            (* tuples? *)
            | _ -> None
            )
        | CompIf _ -> None
     )
   in 
   let new_names = new_vars |> List.map (fun name ->
       Ast.str_of_name name, Ast.LocalVar
   ) in
   with_added_env new_names env (fun () -> ke e);

   (* TODO: should fold and use new env *)
   xs |> List.iter (function
     | CompFor (e1, e2) -> 
          v (Expr e1); v (Expr e2)
     | CompIf e ->
          v (Expr e)
    )
  in    

  (* would be better to use a classic recursive with environment visit *)
  let visitor = V.mk_visitor { V.default_visitor with
    (* No need to resolve at the definition sites (for parameters, locals).
     * This will be patterned-match specially anyway in the highlighter. What
     * you want is to tag the use sites, and to maintain the right environment.
     *)
    V.kexpr = (fun (k, v) x ->
      match x with
      | Name (name, ctx, resolved) ->
          (match ctx with
          | Load | AugLoad ->
            (* assert resolved = NotResolved *)
            let s = Ast.str_of_name name in
            (match List.assoc_opt s !(env.names) with
            | Some x -> resolved := x
            | None -> () (* will be tagged as Error by highlighter later *)
            )
          | Store | AugStore ->
            let kind = 
              let s = Ast.str_of_name name in
              match List.assoc_opt s !(env.names) with
              (* can happen if had a 'Global' declaration before *)
              | Some x -> x
              | None ->
                (match !(env.ctx) with
                | AtToplevel -> GlobalVar
                | InClass -> ClassField
                | InFunction -> LocalVar
                )
            in
            env |> add_name_env name kind;
            resolved := kind; (* optional *)
            
          | Del -> (* should remove from env *)
             ()
          | Param -> 
            resolved := Parameter; (* optional *)
          );
          k x
      | Tuple (CompForIf x, _)
      | List (CompForIf x, _)
        (* bugfix: do not pass just k here, because we want to intercept
         * the processing of 'e' too!
         *)
        -> comprehension (fun e -> v (Expr e)) v x
      | DictOrSet (CompForIf x) -> 
        comprehension (fun elt -> v (DictElem elt)) v x

      (* general case *)
      | _ -> k x
    );
    V.kstmt = (fun (k, v) x ->
      match x with
      | FunctionDef (name, params, _typopt, _body, _decorators) ->
          let new_params = params_of_parameters (params: parameters) in
          let new_names = new_params |> List.map (fun name ->
               Ast.str_of_name name, Ast.Parameter
          ) in
          with_added_env new_names env (fun () -> 
            with_new_context InFunction env (fun () ->
               k x              
          ));
         (* nested function *)
         if !(env.ctx) = InFunction
         then env |> add_name_env name (LocalVar);
     | ClassDef (name, _bases, _body, _decorators) ->
           env |> add_name_env name (ImportedEntity [name]); (* could be more precise *)
           with_new_context InClass env (fun () ->
               k x              
            )
    
     | Import (aliases) ->
         aliases |> List.iter (fun (dotted_name, asname_opt) ->
           asname_opt |> Common.do_option (fun asname ->
             env |> add_name_env asname (ImportedModule dotted_name)
           );
         );
         k x

     | ImportFrom (dotted_name, aliases, _) ->
         aliases |> List.iter (fun (name, asname_opt) ->
           let entity = dotted_name @ [name] in
           (match asname_opt with
           | None -> 
             env |> add_name_env name (ImportedEntity entity);
           | Some asname ->
             env |> add_name_env asname (ImportedEntity entity)
           );
         );
         k x
     | With (e, eopt, stmts) ->
       v (Expr e);
       (match eopt with
       | None -> v (Stmts stmts)
       | Some (Name (name, _ctx, _res)) ->
          (* the scope of name is valid only inside the body, but the
           * body may define variables that are used then outside the with
           * so simpler to use add_name_env() here, not with_add_env()
          let new_names = (fst name, LocalVar)::!(env.names) in
          with_added_env new_names env (fun () ->
            v (Stmts stmts)
          )
           *)
          env |> add_name_env name LocalVar;
          v (Stmts stmts);
       (* todo: tuples? *)
       | Some e -> 
           v (Expr e);
           v (Stmts stmts)
       )
     | TryExcept (stmts1, excepts, stmts2) ->
       v (Stmts stmts1);
       excepts |> List.iter (fun (ExceptHandler (_typ, e, body)) ->
         match e with
         | None -> v (Stmts body)
         | Some (Name (name, _ctx, _res)) ->
           let new_names = (fst name, LocalVar)::!(env.names) in
           with_added_env new_names env (fun () ->
             v (Stmts body)
           )
         (* tuples? *)
         | Some e -> 
            v (Expr e);
            v (Stmts body)
       );
       v (Stmts stmts2);

     | Global names ->
       names |> List.iter (fun name -> env |> add_name_env name GlobalVar;)
    
     (* TODO: NonLocal!! *) 

     (* general case *)
     | _ -> k x
    );  
  } in
  visitor (Program prog)