Refactor request and document process

ocaml-lsp-server/src/custom_requests/req_type_enclosing.ml

@@ -75,13 +75,10 @@ let of_yojson_exn = function
       in
       raise_invalid_params ~data ~message:"Unexpected params format" ())
 
-let overlap_with_range_end range = function
-  | None -> true
-  | Some position ->
-    let lend = range.Range.end_ in
-    if lend.line = position.Position.line then
-      lend.character > position.character
-    else lend.line > position.line
+let overlap_with_range_end range position =
+  let lend = range.Range.end_ in
+  if lend.line = position.Position.line then lend.character > position.character
+  else lend.line > position.line
 
 let render_result index result =
   let typ, enclosings =
@@ -128,24 +125,49 @@ let get_first_enclosing_index range_end enclosings =
   in
   aux 0 enclosings
 
-let dispatch_type_enclosing text_document_position index range_end pipeline =
-  let position = get_logical_position text_document_position in
+let remove_enclosings_duplicata enclosings =
+  enclosings
+  |> List.map ~f:(fun (loc, _, _) -> Range.of_loc loc)
+  |> Merlin_utils.Std.List.merge_cons ~f:(fun a_range b_range ->
+         if Range.compare a_range b_range = Eq then Some b_range else None)
+
+let dispatch_command pipeline command =
+  match Query_commands.dispatch pipeline command with
+  | (_, `String typ, _) :: enclosings ->
+    Some (typ, remove_enclosings_duplicata enclosings)
+  | _ -> None
+
+let dispatch_with_range_end pipeline position index range_end =
+  (* merlin's `type-enclosing` command takes a position and returns a list of
+     increasing enclosures around that position. If it is given the [index]
+     parameter, it annotates the corresponding enclosing with its type.
+
+     As the request would like to allow the target of an interval, we want to
+     truncate the list of enclosures that include the interval. Something merlin
+     cannot do.
+
+     We use a little hack where we use the `type-enclosing` command (with a
+     negative index, so as not to make unnecessary computations) to calculate
+     the enclosings around the given position. Then, we look for the index
+     corresponding to the first enclosing included in the range which will act
+     as an offset to calculate the real index, relative to the range *)
   let dummy_command = make_enclosing_command position (-1) in
   let enclosings = Query_commands.dispatch pipeline dummy_command in
   Option.bind
     (get_first_enclosing_index range_end enclosings)
     ~f:(fun first_index ->
       let command = make_enclosing_command position (first_index + index) in
-      match Query_commands.dispatch pipeline command with
-      | (_, `String typ, _) :: enclosings ->
-        Some
-          ( typ
-          , enclosings
-            |> List.map ~f:(fun (loc, _, _) -> Range.of_loc loc)
-            |> Merlin_utils.Std.List.merge_cons ~f:(fun a_range b_range ->
-                   if Range.compare a_range b_range = Eq then Some b_range
-                   else None) )
-      | _ -> None)
+      dispatch_command pipeline command)
+
+let dispatch_without_range_end pipeline position index =
+  let command = make_enclosing_command position index in
+  dispatch_command pipeline command
+
+let dispatch_type_enclosing text_document_position index range_end pipeline =
+  let position = get_logical_position text_document_position in
+  match range_end with
+  | None -> dispatch_without_range_end pipeline position index
+  | Some range_end -> dispatch_with_range_end pipeline position index range_end
 
 let on_request ~params state =
   Fiber.of_thunk (fun () ->