Source file sexp_handler.ml

(*********************************************************************************)
(*  Dunolint - A tool to lint and help manage files in dune projects             *)
(*  Copyright (C) 2024-2025 Mathieu Barbin <mathieu.barbin@gmail.com>            *)
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(*  This file is part of Dunolint.                                               *)
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(*********************************************************************************)

module type S = Sexp_handler_intf.S

let replace_field ~sexps_rewriter ~field ~new_field =
  let file_rewriter = Sexps_rewriter.file_rewriter sexps_rewriter in
  if not ([%equal: Sexp.t] field new_field)
  then
    File_rewriter.replace
      file_rewriter
      ~range:(Sexps_rewriter.range sexps_rewriter field)
      ~text:(Sexp.to_string_hum new_field)
;;

let find (type a) (module M : S with type t = a) ~sexps_rewriter ~fields =
  List.find_map fields ~f:(fun field ->
    match (field : Sexp.t) with
    | List (Atom name :: _) when String.equal name M.field_name ->
      Some (M.read ~sexps_rewriter ~field)
    | _ -> None)
;;

let get_args ~field_name ~sexps_rewriter ~field =
  match field with
  | Sexp.List (Atom field_name' :: args) when String.equal field_name field_name' -> args
  | _ ->
    Err.raise
      ~loc:(Sexps_rewriter.loc sexps_rewriter field)
      Pp.O.
        [ Pp.text "Unexpected "
          ++ Pp_tty.kwd (module String) field_name
          ++ Pp.text " field."
        ]
;;

module Make_sexpable
    (M : sig
       val field_name : string
     end)
    (S : Sexpable.S) =
struct
  type t = S.t [@@deriving sexp_of]

  let field_name = M.field_name

  let read ~sexps_rewriter ~field =
    match field with
    | Sexp.List [ Atom field_name; value ] when String.equal field_name M.field_name ->
      S.t_of_sexp value
    | _ ->
      Err.raise
        ~loc:(Sexps_rewriter.loc sexps_rewriter field)
        Pp.O.
          [ Pp.textf "Unexpected [Sexp] for field "
            ++ Pp_tty.kwd (module String) M.field_name
            ++ Pp.text "."
          ]
  ;;

  let write (t : t) = Sexp.List [ Atom M.field_name; S.sexp_of_t t ]

  let rewrite (t : t) ~sexps_rewriter ~field =
    replace_field ~sexps_rewriter ~field ~new_field:(write t)
  ;;
end

module Make_atom (M : sig
    val field_name : string
  end) =
  Make_sexpable (M) (String)

module Make_sexps (M : sig
    val field_name : string
  end) =
struct
  type t = Sexp.t list [@@deriving sexp_of]

  let field_name = M.field_name

  let read ~sexps_rewriter ~field =
    get_args ~field_name:M.field_name ~sexps_rewriter ~field
  ;;

  let write (t : t) = Sexp.List (Atom M.field_name :: t)

  let rewrite (t : t) ~sexps_rewriter ~field =
    replace_field ~sexps_rewriter ~field ~new_field:(write t)
  ;;
end

let insert_new_fields ~sexps_rewriter ~indicative_field_ordering ~fields ~new_fields =
  let new_fields =
    List.map new_fields ~f:(fun (field : Sexp.t) ->
      let name =
        match field with
        | List (Atom name :: _) -> name
        | _ ->
          Err.raise
            [ Pp.text "Unexpected field shape"; Pp.text (Sexp.to_string_hum field) ]
      in
      ref false, name, field)
  in
  let file_rewriter = Sexps_rewriter.file_rewriter sexps_rewriter in
  (* We insert all missing fields. *)
  List.iter fields ~f:(fun field ->
    match (field : Sexp.t) with
    | List (Atom field :: _) ->
      List.iter new_fields ~f:(fun (visited, field_name, _) ->
        if String.equal field field_name then visited := true)
    | _ -> ());
  List.iter new_fields ~f:(fun (visited, field_name, new_field) ->
    if not !visited
    then (
      (* To compute the place of insertion we skip input fields as long as they
         appear prior to this field. When we can no longer, we insert after the
         last one. *)
      let field_names_located_before =
        let rec aux acc = function
          | [] -> acc
          | hd :: tl ->
            if String.equal hd field_name then acc else aux (Set.add acc hd) tl
        in
        aux (Set.empty (module String)) indicative_field_ordering
      in
      let pred_field =
        let rec aux last = function
          | [] -> last
          | hd :: tl ->
            (match (hd : Sexp.t) with
             | List (Atom name :: _) ->
               if Set.mem field_names_located_before name then aux hd tl else last
             | _ -> last)
        in
        match fields with
        | hd :: tl -> aux hd tl
        | [] ->
          Err.raise
            ~loc:(Loc.of_file ~path:(Sexps_rewriter.path sexps_rewriter))
            [ Pp.textf "Existing stanza in dune file expected to have at least one field."
            ]
      in
      let pred_loc = Sexps_rewriter.loc sexps_rewriter pred_field in
      let indentation =
        (* The intention here is to help when auto fmt is not
           available for that dune file. *)
        let pred_pos = Loc.start pred_loc in
        let pred_indent = pred_pos.pos_cnum - pred_pos.pos_bol in
        String.make pred_indent ' '
      in
      File_rewriter.insert
        file_rewriter
        ~offset:(Loc.stop_offset pred_loc)
        ~text:("\n" ^ indentation ^ Sexp.to_string_hum new_field)))
;;