Struggles adding Brr support to try-eio / codemirror merlin auto completion

Learning
1

I’m trying to add support for Brr to try-eio repl / codemirror. The error I am getting is:

merlin_worker.bc.js:5482 Fatal error: exception Ocaml_typing.Persistent_env.Error(_)
MlFakeFd_out.write @ merlin_worker.bc.js:5482
caml_ml_flush @ merlin_worker.bc.js:3553
caml_ml_output_bytes @ merlin_worker.bc.js:6206
caml_ml_output @ merlin_worker.bc.js:6215
caml_ml_output_char @ merlin_worker.bc.js:6459
caml_call2 @ merlin_worker.bc.js:17686
output_acc @ merlin_worker.bc.js:21118
caml_call2 @ merlin_worker.bc.js:22538
_h_ @ merlin_worker.bc.js:22547
caml_call1 @ merlin_worker.bc.js:17683
make_printf$0 @ merlin_worker.bc.js:20416
make_printf @ merlin_worker.bc.js:20794
width @ merlin_worker.bc.js:20397
caml_call_gen @ merlin_worker.bc.js:1701
caml_call_gen @ merlin_worker.bc.js:1706
caml_call2 @ merlin_worker.bc.js:23233
default_uncaught_exception_han @ merlin_worker.bc.js:23604
caml_call2 @ merlin_worker.bc.js:23233
handle_uncaught_exception @ merlin_worker.bc.js:23628
caml_call_gen @ merlin_worker.bc.js:1701
caml_fatal_uncaught_exception @ merlin_worker.bc.js:6075
(anonymous) @ merlin_worker.bc.js:8325
error (async)
caml_setup_uncaught_exception_handler @ merlin_worker.bc.js:8321
(anonymous) @ merlin_worker.bc.js:8329
_build/default/repl/merlin_worker.bc.js @ merlin_worker.bc.js:9056
__require2 @ merlin_worker.bc.js:12
(anonymous) @ merlin_worker.bc.js:171072
(anonymous) @ merlin_worker.bc.js:171073

The way I tried to setup this up was updating dune to include brr:

(data_only_dirs stdlib brr)

(library
 (name merlin_js_worker_static)
 (modules static_files)
 (preprocess
  (pps ppx_blob))
 (preprocessor_deps
  (glob_files stdlib/*.cmi)
  (glob_files brr/*.cmi)))

(rule
 (target static_files.ml)
 (deps
  (glob_files stdlib/*.cmi)
  (glob_files brr/*.cmi))
 (action
  (run ocaml %{dep:gen_static.ml})))

and copying over relevant cmi filesinto brr/* , see:

brr/
brr/brr_ocaml_poke.cmi
brr/brr_note_legacy.cmi
brr/jstr.cmi
brr/brr_io.cmi
brr/jv.cmi
brr/fut.cmi
brr/brr_poked.cmi
brr/brr_canvas.cmi
brr/brr_ocaml_poke_ui.cmi
brr/brr_poke.cmi
brr/brr_webworkers.cmi
brr/brr_webcrypto.cmi
brr/brr_note_kit.cmi
brr/brr_note.cmi
brr/brr_webaudio.cmi
brr/brr.cmi
brr/brr_webmidi.cmi
stdlib/
stdlib/eio__core__Debug.cmi
stdlib/stdlib__String.cmi
stdlib/stdlib__Lazy.cmi
stdlib/eio__Fs.cmi
stdlib/eio__.cmi
stdlib/eio__Generic.cmi
stdlib/unix.cmi
stdlib/stdlib__Char.cmi
stdlib/stdlib__Set.cmi
stdlib/stdlib__List.cmi
stdlib/arith_status.cmi
stdlib/stdlib__Oo.cmi
stdlib/stdlib.cmi
stdlib/stdlib__Stream.cmi
stdlib/stdlib__Semaphore.cmi
stdlib/eio__core__Hook.cmi
stdlib/stdlib__Bigarray.cmi
stdlib/stdlib__Scanf.cmi
stdlib/stdlib__Float.cmi
stdlib/stdlib__Option.cmi
stdlib/stdlib__BytesLabels.cmi
stdlib/dynlink.cmi
stdlib/eio_mock__Handler.cmi
stdlib/nat.cmi
stdlib/stdlib__Weak.cmi
stdlib/stdlib__Seq.cmi
stdlib/stdlib__In_channel.cmi
stdlib/eio__Buf_write.cmi
stdlib/ratio.cmi
stdlib/stdlib__Queue.cmi
stdlib/camlinternalMod.cmi
stdlib/stdlib__ArrayLabels.cmi
stdlib/stdlib__Int32.cmi
stdlib/stdlib__Mutex.cmi
stdlib/stdlib__Result.cmi
stdlib/eio__Path.cmi
stdlib/stdlib__Array.cmi
stdlib/stdlib__Random.cmi
stdlib/eio_mock__Clock.cmi
stdlib/camlinternalFormatBasics.cmi
stdlib/eio_mock__Net.cmi
stdlib/stdlib__StdLabels.cmi
stdlib/stdlib__Either.cmi
stdlib/stdlib__Ephemeron.cmi
stdlib/stdlib__Callback.cmi
stdlib/stdlib__Printf.cmi
stdlib/profiling.cmi
stdlib/big_int.cmi
stdlib/stdlib__Marshal.cmi
stdlib/camlinternalOO.cmi
stdlib/camlinternalFormat.cmi
stdlib/eio__core__Waiters.cmi
stdlib/eio__Time.cmi
stdlib/eio__Stream.cmi
stdlib/topdirs.cmi
stdlib/stdlib__Bytes.cmi
stdlib/camlinternalAtomic.cmi
stdlib/bigarray.cmi
stdlib/stdlib__Bool.cmi
stdlib/eio__Flow.cmi
stdlib/stdlib__Condition.cmi
stdlib/stdlib__Nativeint.cmi
stdlib/eio_mock__Backend.cmi
stdlib/stdlib__Uchar.cmi
stdlib/stdlib__Obj.cmi
stdlib/stdlib__Genlex.cmi
stdlib/camlinternalLazy.cmi
stdlib/num.cmi
stdlib/eio__Semaphore.cmi
stdlib/std_exit.cmi
stdlib/eio__core__Promise.cmi
stdlib/stdlib__Map.cmi
stdlib/eio__core__Switch.cmi
stdlib/stdlib__Domain.cmi
stdlib/stdlib__Int.cmi
stdlib/eio.cmi
stdlib/stdlib__ListLabels.cmi
stdlib/eio_mock__Action.cmi
stdlib/stdlib__Arg.cmi
stdlib/stdlib__Int64.cmi
stdlib/stdlib__StringLabels.cmi
stdlib/eio__core__.cmi
stdlib/eio_mock__.cmi
stdlib/stdlib__Parsing.cmi
stdlib/stdlib__Hashtbl.cmi
stdlib/eio__core__Exn.cmi
stdlib/stdlib__Lexing.cmi
stdlib/stdlib__Fun.cmi
stdlib/stdlib__Printexc.cmi
stdlib/stdlib__Pervasives.cmi
stdlib/stdlib__Out_channel.cmi
stdlib/eio__File.cmi
stdlib/eio__Net.cmi
stdlib/str.cmi
stdlib/eio__core__Ctf.cmi
stdlib/stdlib__Digest.cmi
stdlib/eio__core__Suspend.cmi
stdlib/eio__core.cmi
stdlib/unixLabels.cmi
stdlib/eio__core__Single_waiter.cmi
stdlib/eio__Buf_read.cmi
stdlib/stdlib__Effect.cmi
stdlib/eio__Condition.cmi
stdlib/eio_mock.cmi
stdlib/eio_mock__Flow.cmi
stdlib/stdlib__Unit.cmi
stdlib/stdlib__Buffer.cmi
stdlib/eio__Domain_manager.cmi
stdlib/stdlib__Stack.cmi
stdlib/eio__Eio_mutex.cmi
stdlib/stdlib__MoreLabels.cmi
stdlib/eio__core__Cancel.cmi
stdlib/stdlib__Gc.cmi
stdlib/stdlib__Complex.cmi
stdlib/stdlib__Atomic.cmi
stdlib/stdlib__Sys.cmi
stdlib/eio__core__Fiber.cmi
stdlib/stdlib__Filename.cmi
stdlib/stdlib__Format.cmi

I am trying to figure out the next step to try in debugging this. The XY problem is I am trying to learn how to add modules to the try-eio/codemirror auto completion menu.

Thanks!

2

One step of progress to this would be if, on this error, we can get the merlin worker thread to catch it instead of crashing the merlin_worker thread (and losing all auto completion).

3

Have you updated gen_static.ml ?

4

Good question. It is currently commented out because I went a step further and copied brr/* into stdlib/* as it seems parts of merlin_worker has stdlib hardcoded:

#use "topfind" ;;
#require "unix";;


let rec iter_cmi ~f dir_handle =
  match Unix.readdir dir_handle with
  | exception End_of_file -> ()
  | file ->
    if Filename.extension file = ".cmi" then
      f file;
    iter_cmi ~f dir_handle

let () =
  let cwd = Unix.getcwd () in
  let out = open_out "static_files.ml" in

  Printf.fprintf out "let stdlib_cmis = [";

  let stdlib = Filename.concat cwd "stdlib" in
  let dir = Unix.opendir stdlib in
  iter_cmi ~f:(fun file ->
    let fullpath = Filename.concat stdlib file in
    Printf.fprintf out "(%S,[%%blob %S]);" fullpath fullpath) dir;

  (*
  let stdlib = Filename.concat cwd "brr" in
  let dir = Unix.opendir stdlib in
  iter_cmi ~f:(fun file ->
    let fullpath = Filename.concat stdlib file in
    Printf.fprintf out "(%S,[%%blob %S]);" fullpath fullpath) dir;
     *)

  Printf.fprintf out "]\n";

  close_out out

I think I am making progress on this. I found the right place in merlin_worker to try/catch and return empty list of completions on error – however, it appears CodeMirror is still throwing an error of its own.

5

I got something useful:

The files /static/stdlib/stdlib.cmi and /static/stdlib/brr.cmi\nmake inconsistent assumptions over interface Stdlib

I suspect this is because I used the *.cmi from git for stdlib, and the *.cmi from ~/.opam for brr.

6

In case anyone else runs into this, the ‘solution’ for me was:

cp ~/.opam/default/lib/ocaml/**/*.cmi .
cp ~/.opam/default/lib/brr/**/*.cmi .