fix: run some parts of notification handling sequentially

src/jsonrpc2.ml

@@ -316,14 +316,22 @@ module Make (IO : IO) : S with module IO = IO = struct
     When launching an LSP server using [Server.Make.server], the
     natural choice for it is [s#get_status = `ReceivedExit] *)
   let run ?(shutdown = fun _ -> false) (self : t) : unit IO.t =
+    let async f =
+      self.s#spawn_query_handler f;
+      IO.return ()
+    in
+
     let process_msg r =
       let module M = Jsonrpc.Packet in
       match r with
-      | M.Notification n -> handle_notification self n
-      | M.Request r -> handle_request self r
-      | M.Response r -> handle_response self r
-      | M.Batch_response rs -> handle_batch_response self rs
-      | M.Batch_call cs -> handle_batch_call self cs
+      | M.Notification n ->
+        (* NOTE: we handle some notifications sequentially, because
+           they do not commute (e.g. "TextDocumentDidChange" with incremental sync) *)
+        handle_notification self n
+      | M.Request r -> async (fun () -> handle_request self r)
+      | M.Response r -> async (fun () -> handle_response self r)
+      | M.Batch_response rs -> async (fun () -> handle_batch_response self rs)
+      | M.Batch_call cs -> async (fun () -> handle_batch_call self cs)
     in
     let rec loop () =
       if shutdown () then
@@ -332,7 +340,7 @@ module Make (IO : IO) : S with module IO = IO = struct
         let* r = read_msg self in
         match r with
         | Ok r ->
-          self.s#spawn_query_handler (fun () -> process_msg r);
+          let* () = process_msg r in
           loop ()
         | Error e -> IO.fail e
     in

src/server.ml

@@ -74,6 +74,10 @@ module Make (IO : IO) = struct
           @since NEXT_RELEASE *)
     end
 
+  let async (self : #base_server) f : unit IO.t =
+    self#spawn_query_handler f;
+    IO.return ()
+
   (** A wrapper to more easily reply to notifications *)
   class notify_back ~notify_back ~server_request ~workDoneToken
     ~partialResultToken:_ ?version ?(uri : DocumentUri.t option) () =
@@ -308,8 +312,8 @@ module Make (IO : IO) = struct
       (** List symbols in this document.
         @since 0.3 *)
 
-      method on_unknown_request ~notify_back:(_ : notify_back) ~server_request:_ ~id:_ meth params
-          : Yojson.Safe.t IO.t =
+      method on_unknown_request ~notify_back:(_ : notify_back) ~server_request:_
+          ~id:_ _meth _params : Yojson.Safe.t IO.t =
         IO.failwith "unhandled request"
 
       method on_request : type r.
@@ -484,7 +488,8 @@ module Make (IO : IO) = struct
                 ~workDoneToken:None ~partialResultToken:None ~notify_back
                 ~server_request ()
             in
-            self#on_unknown_request ~notify_back ~server_request ~id r.meth r.params
+            self#on_unknown_request ~notify_back ~server_request ~id r.meth
+              r.params
 
       method virtual on_notif_doc_did_open
           : notify_back:notify_back ->
@@ -536,9 +541,11 @@ module Make (IO : IO) = struct
             }
           in
           Hashtbl.replace docs doc.uri st;
+
+          async self (fun () ->
               self#on_notif_doc_did_open
                 ~notify_back:(notify_back : notify_back)
-            doc ~content:st.content
+                doc ~content:st.content)
         | Lsp.Client_notification.TextDocumentDidClose { textDocument = doc } ->
           Log.debug (fun k ->
               k "notif: did close '%s'" (DocumentUri.to_path doc.uri));
@@ -547,9 +554,11 @@ module Make (IO : IO) = struct
               ~workDoneToken:None ~partialResultToken:None ~uri:doc.uri
               ~notify_back ~server_request ()
           in
+
+          async self (fun () ->
               self#on_notif_doc_did_close
                 ~notify_back:(notify_back : notify_back)
-            doc
+                doc)
         | Lsp.Client_notification.TextDocumentDidChange
             { textDocument = doc; contentChanges = c } ->
           Log.debug (fun k ->
@@ -599,11 +608,13 @@ module Make (IO : IO) = struct
           in
 
           Hashtbl.replace docs doc.uri new_st;
+
+          async self (fun () ->
               self#on_notif_doc_did_change
                 ~notify_back:(notify_back : notify_back)
                 doc c
                 ~old_content:(Lsp.Text_document.text old_doc)
-            ~new_content:new_st.content
+                ~new_content:new_st.content)
         | Lsp.Client_notification.Exit ->
           status <- `ReceivedExit;
           IO.return ()
@@ -625,15 +636,18 @@ module Make (IO : IO) = struct
               ~workDoneToken:None ~partialResultToken:None ~notify_back
               ~server_request ()
           in
+
+          async self (fun () ->
               self#on_notification_unhandled
                 ~notify_back:(notify_back : notify_back)
-            n
+                n)
         | Lsp.Client_notification.UnknownNotification n ->
           let notify_back =
             new notify_back
               ~workDoneToken:None ~partialResultToken:None ~notify_back
               ~server_request ()
           in
-          self#on_unknown_notification ~notify_back n
+
+          async self (fun () -> self#on_unknown_notification ~notify_back n)
     end
 end