add lsp error notification mechanism

compiler/catala_utils/message.ml

@@ -275,10 +275,10 @@ module Content = struct
     restore_ppf ();
     Format.pp_print_newline ppf ()
 
-  let emit ?(pp_marker = pp_marker) (content : t) (target : level) : unit =
+  let emit ?ppf ?(pp_marker = pp_marker) (content : t) (target : level) : unit =
+    let ppf = Option.value ~default:(get_ppf target) ppf in
     match Global.options.message_format with
     | Global.Human -> (
-      let ppf = get_ppf target in
       match target with
       | Debug | Log -> basic_msg ~pp_marker ppf target content
       | Result | Warning | Error -> fancy_msg ~pp_marker ppf target content)
@@ -288,7 +288,6 @@ module Content = struct
          message everywhere there is not a more precise message. If we can't
          find a position without a more precise message, we just take the first
          position in the list to pair with the message. *)
-      let ppf = get_ppf target in
       Format.pp_print_list ~pp_sep:Format.pp_print_newline
         (fun ppf elt ->
           let pos, message =
@@ -327,10 +326,10 @@ module Content = struct
         ppf content;
       Format.pp_print_newline ppf ()
 
-  let emit_n (target : level) = function
+  let emit_n ?ppf (target : level) = function
     | [content] -> emit content target
     | contents ->
-      let ppf = get_ppf target in
+      let ppf = Option.value ~default:(get_ppf target) ppf in
       let len = List.length contents in
       List.iteri
         (fun i c ->
@@ -340,7 +339,7 @@ module Content = struct
           emit ~pp_marker c target)
         contents
 
-  let emit (content : t) (target : level) = emit content target
+  let emit ?ppf (content : t) (target : level) = emit ?ppf content target
 end
 
 open Content
@@ -350,6 +349,18 @@ open Content
 exception CompilerError of Content.t
 exception CompilerErrors of Content.t list
 
+type lsp_error_kind = Lexing | Parsing | Typing | Generic
+
+type lsp_error = {
+  kind : lsp_error_kind;
+  message : Format.formatter -> unit;
+  pos : Pos.t option;
+  suggestion : string list option;
+}
+
+let global_error_hook = ref None
+let register_lsp_error_notifier f = global_error_hook := Some f
+
 (** {1 Error printing} *)
 
 type ('a, 'b) emitter =
@@ -425,7 +436,18 @@ let log = make ~level:Log ~cont:emit
 let result = make ~level:Result ~cont:emit
 let results r = emit (List.flatten (List.map of_result r)) Result
 let warning = make ~level:Warning ~cont:emit
-let error = make ~level:Error ~cont:(fun m _ -> raise (CompilerError m))
+
+let error ?(kind = Generic) : ('a, 'exn) emitter =
+ fun ?header ?internal ?pos ?pos_msg ?extra_pos ?fmt_pos ?outcome ?suggestion
+     fmt ->
+  make ?header ?internal ?pos ?pos_msg ?extra_pos ?fmt_pos ?outcome ?suggestion
+    fmt ~level:Error ~cont:(fun m _ ->
+      Option.iter
+        (fun f ->
+          let message ppf = Content.emit ~ppf m Error in
+          f { kind; message; pos; suggestion })
+        !global_error_hook;
+      raise (CompilerError m))
 
 (* Multiple errors handling *)
 
@@ -436,8 +458,16 @@ type global_errors = {
 
 let global_errors = { errors = None; stop_on_error = false }
 
-let delayed_error x =
-  make ~level:Error ~cont:(fun m _ ->
+let delayed_error ?(kind = Generic) x : ('a, 'exn) emitter =
+ fun ?header ?internal ?pos ?pos_msg ?extra_pos ?fmt_pos ?outcome ?suggestion
+     fmt ->
+  make ?header ?internal ?pos ?pos_msg ?extra_pos ?fmt_pos ?outcome ?suggestion
+    fmt ~level:Error ~cont:(fun m _ ->
+      Option.iter
+        (fun f ->
+          let message ppf = Content.emit ~ppf m Error in
+          f { kind; message; pos; suggestion })
+        !global_error_hook;
       if global_errors.stop_on_error then raise (CompilerError m);
       match global_errors.errors with
       | None ->
@@ -458,6 +488,7 @@ let with_delayed_errors
       "delayed error called outside scope: encapsulate using \
        'with_delayed_errors' first");
   global_errors.stop_on_error <- stop_on_error;
+  try
     let r = f () in
     match global_errors.errors with
     | None -> error ~internal:true "intertwined delayed error scope"
@@ -470,3 +501,6 @@ let with_delayed_errors
     | Some errs ->
       global_errors.errors <- None;
       raise (CompilerErrors (List.rev errs))
+  with e ->
+    global_errors.errors <- None;
+    raise e

compiler/catala_utils/message.mli

@@ -54,8 +54,8 @@ module Content : sig
 
   (** {2 Content emission}*)
 
-  val emit : t -> level -> unit
-  val emit_n : level -> t list -> unit
+  val emit_n : ?ppf:Format.formatter -> level -> t list -> unit
+  val emit : ?ppf:Format.formatter -> t -> level -> unit
 end
 
 (** This functions emits the message according to the emission type defined by
@@ -66,6 +66,17 @@ end
 exception CompilerError of Content.t
 exception CompilerErrors of Content.t list
 
+type lsp_error_kind = Lexing | Parsing | Typing | Generic
+
+type lsp_error = {
+  kind : lsp_error_kind;
+  message : Content.message;
+  pos : Pos.t option;
+  suggestion : string list option;
+}
+
+val register_lsp_error_notifier : (lsp_error -> unit) -> unit
+
 (** {1 Some formatting helpers}*)
 
 val unformat : (Format.formatter -> unit) -> string
@@ -105,7 +116,7 @@ val log : ('a, unit) emitter
 val debug : ('a, unit) emitter
 val result : ('a, unit) emitter
 val warning : ('a, unit) emitter
-val error : ('a, 'exn) emitter
+val error : ?kind:lsp_error_kind -> ('a, 'exn) emitter
 val results : Content.message list -> unit
 
 (** Multiple errors *)
@@ -119,4 +130,4 @@ val with_delayed_errors : ?stop_on_error:bool -> (unit -> 'a) -> 'a
     @raise CompilerError
       on the first error encountered when the [stop_on_error] flag is set. *)
 
-val delayed_error : 'b -> ('a, 'b) emitter
+val delayed_error : ?kind:lsp_error_kind -> 'b -> ('a, 'b) emitter