Refactor suggestions

compiler/catala_utils/suggestions.ml

@@ -48,51 +48,34 @@ let levenshtein_distance (s : string) (t : string) : int =
 
   d.(m).(n)
 
-(*We create a list composed by strings that satisfy the following rule : they
-  have the same levenshtein distance, which is the minimum distance between the
-  reference word "keyword" and all the strings in "candidates" (with the
-  condition that this minimum is equal to or less than one third of the length
-  of keyword + 1, in order to get suggestions close to "keyword")*)
-let suggestion_minimum_levenshtein_distance_association
-    (candidates : string list)
-    (keyword : string) : string list =
-  let rec strings_minimum_levenshtein_distance
-      (minimum : int)
-      (result : string list)
-      (candidates' : string list) : string list =
-    (*As we iterate through the "candidates'" list, we create a list "result"
-      with all strings that have the last minimum levenshtein distance found
-      ("minimum").*)
-    match candidates' with
-    (*When a new minimum levenshtein distance is found, the new result list is
-      our new element "current_string" followed by strings that have the same
-      minimum distance. It will be the "result" list if there is no levenshtein
-      distance smaller than this new minimum.*)
-    | current_string :: tail ->
-      let current_levenshtein_distance =
-        levenshtein_distance current_string keyword
-      in
-      if current_levenshtein_distance < minimum then
-        strings_minimum_levenshtein_distance current_levenshtein_distance
-          [current_string] tail
-        (*The "result" list is updated (we append "current_string" to "result")
-          when a new string shares the same minimum levenshtein distance
-          "minimum"*)
-      else if current_levenshtein_distance = minimum then
-        strings_minimum_levenshtein_distance minimum
-          (result @ [current_string])
-          tail
-        (*If a levenshtein distance greater than the minimum is found, "result"
-          doesn't change*)
-      else strings_minimum_levenshtein_distance minimum result tail
-    (*The "result" list is returned at the end of the "candidates'" list.*)
-    | [] -> result
+module M = Stdlib.Map.Make (Int)
+
+let compute_candidates (candidates : string list) (word : string) :
+    string list M.t =
+  List.fold_left
+    (fun m candidate ->
+      let distance = levenshtein_distance word candidate in
+      M.update distance
+        (function None -> Some [candidate] | Some l -> Some (candidate :: l))
+        m)
+    M.empty candidates
+
+let best_candidates candidates word =
+  let candidates = compute_candidates candidates word in
+  M.choose_opt candidates |> function None -> [] | Some (_, l) -> List.rev l
+
+let sorted_candidates ?(max_elements = 5) suggs given =
+  let rec sub acc n = function
+    | [] -> List.rev acc
+    | x :: t when n > 0 -> sub (x :: acc) (pred n) t
+    | _ -> List.rev acc
   in
-  strings_minimum_levenshtein_distance
-    (1 + (String.length keyword / 3))
-    (*In order to select suggestions that are not too far away from the
-      keyword*)
-    [] candidates
+  let candidates =
+    List.map
+      (fun (_, l) -> List.rev l)
+      (M.bindings (compute_candidates suggs given))
+  in
+  List.concat candidates |> sub [] max_elements
 
 let format (ppf : Format.formatter) (suggestions_list : string list) =
   match suggestions_list with

compiler/catala_utils/suggestions.mli

@@ -15,9 +15,20 @@
    License for the specific language governing permissions and limitations under
    the License. *)
 
-val suggestion_minimum_levenshtein_distance_association :
-  string list -> string -> string list
-(**Returns a list of the closest words into {!name:candidates} to the keyword
-   {!name:keyword}*)
+val levenshtein_distance : string -> string -> int
+(** [levenshtein_distance w1 w2] computes the levenshtein distance separating
+    [w1] from [w2]. *)
+
+val best_candidates : string list -> string -> string list
+(** [best_candidates suggestions word] returns the subset of elements in
+    [suggestions] that minimize the levenshtein distance to [word]. Multiple
+    candidates that have a same distance is possible. *)
+
+val sorted_candidates :
+  ?max_elements:int -> string list -> string -> string list
+(** [sorted_candidates ?max_elements suggestions word] sorts the [suggestions]
+    list and retain at most [max_elements] (defaults to 5). This list is ordered
+    by their levenshtein distance to [word], i.e., the first elements are the
+    most similar. *)
 
 val format : Format.formatter -> string list -> unit

compiler/desugared/from_surface.ml

@@ -138,8 +138,7 @@ let raise_error_cons_not_found
     (constructor : string Mark.pos) =
   let constructors = Ident.Map.keys ctxt.local.constructor_idmap in
   let closest_constructors =
-    Suggestions.suggestion_minimum_levenshtein_distance_association constructors
-      (Mark.remove constructor)
+    Suggestions.best_candidates constructors (Mark.remove constructor)
   in
   Message.error
     ~pos_msg:(fun ppf -> Format.fprintf ppf "Here is your code :")

compiler/shared_ast/typing.ml

@@ -618,7 +618,10 @@ and typecheck_expr_top_down :
               "Variable @{<yellow>%s@} is not a declared output of scope %a."
               field A.ScopeName.format scope_out
               ~suggestion:
-                (List.map A.StructField.to_string (A.StructField.Map.keys str))
+                (Suggestions.sorted_candidates
+                   (List.map A.StructField.to_string
+                      (A.StructField.Map.keys str))
+                   field)
           | None ->
             Message.error
               ~extra_pos:
@@ -629,7 +632,10 @@ and typecheck_expr_top_down :
               "Field@ @{<yellow>\"%s\"@}@ does@ not@ belong@ to@ structure@ \
                @{<yellow>\"%a\"@}."
               field A.StructName.format name
-              ~suggestion:(A.Ident.Map.keys ctx.ctx_struct_fields))
+              ~suggestion:
+                (Suggestions.sorted_candidates
+                   (A.Ident.Map.keys ctx.ctx_struct_fields)
+                   field))
       in
       try A.StructName.Map.find name candidate_structs
       with A.StructName.Map.Not_found _ ->

compiler/surface/parser_driver.ml

@@ -105,15 +105,16 @@ module ParserAux (LocalisedLexer : Lexer_common.LocalisedLexer) = struct
 
   let sorted_candidate_tokens lexbuf token_list env =
     let acceptable_tokens =
-      List.filter
-        (fun (_, t) ->
-          I.acceptable (I.input_needed env) t (fst (lexing_positions lexbuf)))
+      List.filter_map
+        (fun ((_, t) as elt) ->
+          if I.acceptable (I.input_needed env) t (fst (lexing_positions lexbuf))
+          then Some elt
+          else None)
         token_list
     in
+    let lexeme = Utf8.lexeme lexbuf in
     let similar_acceptable_tokens =
-      Suggestions.suggestion_minimum_levenshtein_distance_association
-        (List.map (fun (s, _) -> s) acceptable_tokens)
-        (Utf8.lexeme lexbuf)
+      Suggestions.best_candidates (List.map fst acceptable_tokens) lexeme
     in
     let module S = Set.Make (String) in
     let s_toks = S.of_list similar_acceptable_tokens in

tests/default/bad/verbose_errors.catala_en

@@ -50,11 +50,8 @@ $ catala test-scope A
 │   │                       ‾
 ├─ Article
 │
-│ Maybe you wanted to write : "field0", or "field1", or "field2",
-│   or "field3", or "field4", or "field5", or "field6", or "field7",
-│   or "field8", or "field9", or "field10", or "field11", or "field12",
-│   or "field13", or "field14", or "field15", or "field16", or "field17",
-│   or "field18", or "field19", or "o" ?
+│ Maybe you wanted to write : "field0", or "field2", or "field10",
+│   or "field1", or "field3" ?
 └─
 #return code 123#
 ```