Add flag to disable dune diagnostics

--no-dune-diagnostics

ocaml-lsp-server/bin/main.ml

@@ -5,13 +5,17 @@ let () =
   Printexc.record_backtrace true;
   let version = ref false in
   let read_dot_merlin = ref false in
+  let dune_diagnostics = ref true in
   let arg = Lsp.Cli.Arg.create () in
   let spec =
     [ ("--version", Arg.Set version, "print version")
     ; ( "--fallback-read-dot-merlin"
       , Arg.Set read_dot_merlin
       , "read Merlin config from .merlin files. The `dot-merlin-reader` \
          package must be installed" )
+    ; ( "--no-dune-diagnostics"
+      , Arg.Clear dune_diagnostics
+      , "disable dune diagnostics" )
     ]
     @ Cli.Arg.spec arg
   in
@@ -39,7 +43,10 @@ let () =
     let module Exn_with_backtrace = Stdune.Exn_with_backtrace in
     match
       Exn_with_backtrace.try_with
-        (Ocaml_lsp_server.run channel ~read_dot_merlin:!read_dot_merlin)
+        (Ocaml_lsp_server.run
+           channel
+           ~read_dot_merlin:!read_dot_merlin
+           ~dune_diagnostics:!dune_diagnostics)
     with
     | Ok () -> ()
     | Error exn ->

ocaml-lsp-server/src/dune.ml

@@ -114,6 +114,8 @@ module Poll =
               (Result.try_with (fun () -> Io.String_path.read_file s)))
     end)
 
+let enable_diagnostics = ref true
+
 type config =
   { diagnostics : Diagnostics.t
   ; document_store : Document_store.t
@@ -526,14 +528,24 @@ end = struct
                let progress =
                  progress_loop client diagnostics document_store progress
                in
-               let diagnostics =
-                 let dune_root =
-                   DocumentUri.of_path (Registry.Dune.root source)
-                 in
-                 diagnostic_loop ~dune_root client config running diagnostics
+               let additional_fibers =
+                 if !enable_diagnostics then
+                   let diagnostics =
+                     let dune_root =
+                       DocumentUri.of_path (Registry.Dune.root source)
+                     in
+                     diagnostic_loop
+                       ~dune_root
+                       client
+                       config
+                       running
+                       diagnostics
+                   in
+                   [ diagnostics ]
+                 else []
                in
                Fiber.all_concurrently_unit
-                 [ progress; diagnostics; Fiber.Ivar.read finish ]))
+                 (progress :: Fiber.Ivar.read finish :: additional_fibers)))
         ]
     in
     Progress.end_build_if_running progress

ocaml-lsp-server/src/dune.mli

@@ -8,6 +8,9 @@ end
 
 type t
 
+(** enabled by default *)
+val enable_diagnostics : bool ref
+
 val view_promotion_capability : string * Json.t
 
 val run : t -> unit Fiber.t

ocaml-lsp-server/src/ocaml_lsp_server.ml

@@ -916,10 +916,11 @@ let run_in_directory =
   let for_windows = !Merlin_utils.Std.System.run_in_directory in
   fun () -> if Sys.win32 then for_windows else run_in_directory
 
-let run channel ~read_dot_merlin () =
+let run channel ~read_dot_merlin ~dune_diagnostics () =
   Merlin_utils.Lib_config.set_program_name "ocamllsp";
   Merlin_utils.Lib_config.System.set_run_in_directory (run_in_directory ());
   Merlin_config.should_read_dot_merlin := read_dot_merlin;
+  Dune.enable_diagnostics := dune_diagnostics;
   Unix.putenv "__MERLIN_MASTER_PID" (string_of_int (Unix.getpid ()));
   Lev_fiber.run ~sigpipe:`Ignore (fun () ->
       let* input, output = stream_of_channel channel in

ocaml-lsp-server/src/ocaml_lsp_server.mli

@@ -1,4 +1,9 @@
-val run : Lsp.Cli.Channel.t -> read_dot_merlin:bool -> unit -> unit
+val run :
+     Lsp.Cli.Channel.t
+  -> read_dot_merlin:bool
+  -> dune_diagnostics:bool
+  -> unit
+  -> unit
 
 module Diagnostics = Diagnostics
 module Version = Version