Added a global check reporting variables only reads

bin/qsp_parser.ml

@@ -24,6 +24,7 @@ let available_checks =
     snd @@ Qsp_syntax.Check.build (module Qsp_syntax.Nested_strings);
     snd @@ Qsp_syntax.Check.build (module Qsp_syntax.Locations);
     snd @@ Qsp_syntax.Check.build (module Qsp_syntax.Dup_test);
+    snd @@ Qsp_syntax.Check.build (module Qsp_syntax.Write_only);
   ]
 
 let pp_module formatter (module A : Qsp_syntax.S.Analyzer) =

lib/syntax/write_only.ml

@@ -0,0 +1,217 @@
+(** Check all the write_only variables *)
+
+open StdLabels
+
+(** Identifier for the module *)
+let identifier = "write_only"
+
+(** Short description*)
+let description = "Check variables never read"
+
+(** Is the test active or not *)
+let active = ref false
+
+let is_global = true
+
+module Key = struct
+  type t = string
+
+  let equal = String.equal
+  let hash = Hashtbl.hash
+  let compare = String.compare
+end
+
+module StringMap = Hashtbl.Make (Key)
+module Set = Set.Make (Key)
+
+type data = { write : bool; read : bool; position : S.pos list }
+type context = (string * data) StringMap.t
+
+let initialize () = StringMap.create 16
+
+let keywords =
+  [
+    "BACKIMAGE";
+    "$BACKIMAGE";
+    "BCOLOR";
+    "DEBUG";
+    "DISABLESCROLL";
+    "DISABLESUBEX";
+    "FCOLOR";
+    "$FNAME";
+    "FSIZE";
+    "GC";
+    "LCOLOR";
+    "NOSAVE";
+  ]
+  |> Set.of_list
+
+let set_readed :
+    ?update_only:bool -> S.pos -> string -> string -> context -> unit =
+ fun ?(update_only = false) pos identifier filename map ->
+  if not (Set.mem identifier keywords) then
+    match (update_only, StringMap.find_opt map identifier) with
+    | false, None ->
+        StringMap.add map identifier
+          (filename, { write = false; read = true; position = [] })
+    | _, Some (filename, v) ->
+        StringMap.replace map identifier
+          (filename, { v with read = true; position = pos :: v.position })
+    | true, None -> ()
+
+let set_write : S.pos -> string -> string -> context -> unit =
+ fun pos identifier filename map ->
+  if not (Set.mem identifier keywords) then
+    match StringMap.find_opt map identifier with
+    | None ->
+        StringMap.add map identifier
+          (filename, { write = true; read = false; position = pos :: [] })
+    | Some (filename, v) ->
+        StringMap.replace map identifier
+          (filename, { v with write = true; position = pos :: v.position })
+
+module Expression = struct
+  type t = string -> context -> unit
+
+  let v : t -> t = Fun.id
+
+  include Default.Expression (struct
+    type nonrec t = t
+
+    let default _ map = ignore map
+  end)
+
+  let ident : (S.pos, t) S.variable -> t =
+   fun variable filename map ->
+    (* Update the map and set the read flag *)
+    set_readed variable.pos variable.name filename map
+
+  let literal : S.pos -> t T.literal list -> t =
+   fun pos l filename map ->
+    List.iter l ~f:(function
+      | T.Text t ->
+          set_readed pos ~update_only:true (String.uppercase_ascii t) filename
+            map
+      | T.Expression exprs ->
+          (* When the string contains an expression evaluate it *)
+          exprs filename map)
+
+  let function_ : S.pos -> T.function_ -> t list -> t =
+   fun _ _ exprs filename map -> List.iter ~f:(fun v -> v filename map) exprs
+
+  let uoperator : S.pos -> T.uoperator -> t -> t = fun _ _ t map -> t map
+
+  let boperator : S.pos -> T.boperator -> t -> t -> t =
+   fun _ _ t1 t2 filename map ->
+    t1 filename map;
+    t2 filename map
+end
+
+module Instruction = struct
+  type t = Expression.t
+  (** Internal type used in the evaluation *)
+
+  type t' = t
+
+  let v : t -> t' = Fun.id
+
+  type expression = Expression.t
+
+  let location : S.pos -> string -> t = fun _pos _ _ _ -> ()
+
+  let call : S.pos -> T.keywords -> expression list -> t =
+   fun _ op exprs filename map ->
+    match op with
+    | T.KillVar ->
+        (* Killing a variable does not count as reading it *)
+        ()
+    | _ -> List.iter ~f:(fun v -> v filename map) exprs
+
+  let comment : S.pos -> t = fun _ _ _ -> ()
+  let expression : expression -> t = fun expression map -> expression map
+
+  let fold_clause : (expression, t) S.clause -> t =
+   fun clause filename map ->
+    let _, expr, exprs = clause in
+    let () = expr filename map in
+    let () = List.iter ~f:(fun v -> v filename map) exprs in
+    ()
+
+  let if_ :
+      S.pos ->
+      (expression, t) S.clause ->
+      elifs:(expression, t) S.clause list ->
+      else_:(S.pos * t list) option ->
+      t =
+   fun pos clauses ~elifs ~else_ filename map ->
+    ignore pos;
+    let () = fold_clause clauses filename map in
+    let () = List.iter ~f:(fun v -> fold_clause v filename map) elifs in
+    Option.iter
+      (fun (_, exprs) -> List.iter exprs ~f:(fun v -> v filename map))
+      else_;
+    ()
+
+  let act : S.pos -> label:expression -> t list -> t =
+   fun pos ~label exprs filename map ->
+    ignore pos;
+    ignore label;
+    List.iter ~f:(fun v -> v filename map) exprs
+
+  let assign :
+      S.pos ->
+      (S.pos, expression) S.variable ->
+      T.assignation_operator ->
+      expression ->
+      t =
+   fun pos variable op expr filename map ->
+    ignore op;
+    ignore expr;
+    Option.iter (fun v -> v filename map) variable.index;
+    expr filename map;
+    set_write pos variable.name filename map
+end
+
+module Location = struct
+  type t = unit
+  type instruction = string -> context -> unit
+
+  let v : t -> Report.t list = fun _ -> []
+
+  let location : context -> S.pos -> instruction list -> t =
+   fun context pos instructions ->
+    let file_name = (fst pos).Lexing.pos_fname in
+    ignore pos;
+    ignore context;
+    let () = List.iter ~f:(fun v -> v file_name context) instructions in
+    ()
+end
+
+(** Extract the results from the whole parsing *)
+let finalize : context -> (string * Report.t) list =
+ fun map ->
+  let () =
+    StringMap.filter_map_inplace
+      (fun _ (loc, value) ->
+        match value.read && value.write with
+        | true -> None
+        | false -> Some (loc, value))
+      map
+  in
+
+  let report =
+    StringMap.fold
+      (fun ident (loc, value) report ->
+        match value.read with
+        | false ->
+            List.fold_left value.position ~init:report ~f:(fun report pos ->
+                let msg =
+                  Report.debug pos
+                    (String.concat ~sep:" "
+                       [ "The variable"; ident; "is never read" ])
+                in
+                (loc, msg) :: report)
+        | true -> report)
+      map []
+  in
+  report