Experimental ReScript Language Server in OCaml

.github/workflows/ci.yml

@@ -66,12 +66,13 @@ jobs:
             exe-suffix: ".exe"
             dune-profile: release
 
+          # Disable for now. eio and eio_main require ocaml >= 5.2.0
           # Verify that the compiler still builds with the oldest OCaml version we support.
-          - os: ubuntu-24.04
-            ocaml_compiler: ocaml-variants.5.0.0+options,ocaml-option-static
-            node-target: linux-x64
-            rust-target: x86_64-unknown-linux-musl
-            dune-profile: static
+          # - os: ubuntu-24.04
+          #   ocaml_compiler: ocaml-variants.5.0.0+options,ocaml-option-static
+          #   node-target: linux-x64
+          #   rust-target: x86_64-unknown-linux-musl
+          #   dune-profile: static
 
     runs-on: ${{matrix.os}}
 
@@ -107,7 +108,7 @@ jobs:
           # https://github.com/ocaml/setup-ocaml/blob/2f57267f071bc8547dfcb9433ff21d44fffef190/packages/setup-ocaml/src/unix.ts#L48
           # plus OPAM wants cmake
           packages: bubblewrap darcs g++-multilib gcc-multilib mercurial musl-tools rsync cmake
-          version: v4
+          version: v5
 
       - name: Restore rewatch build cache
         id: rewatch-build-cache
@@ -176,6 +177,56 @@ jobs:
             C:\.opam
           key: ${{ env.opam_cache_key }}
 
+      # The static OCaml switch uses musl-gcc. linux-libc-dev installs Linux
+      # headers under /usr/include, but musl-gcc searches the musl include dir.
+      # Link the Linux headers into musl's include path so packages with C stubs
+      # such as uring can include <linux/...> headers.
+      - name: Make Linux headers visible to musl-gcc
+        if: runner.os == 'Linux'
+        run: |
+          set -eux
+
+          # Get the GNU multiarch triplet for the current machine.
+          # Examples:
+          #   x86_64-linux-gnu
+          #   aarch64-linux-gnu
+          GNU_MULTIARCH="$(gcc -print-multiarch)"
+
+          # Convert the GNU triplet into the musl include directory name.
+          # Examples:
+          #   x86_64-linux-gnu  -> x86_64-linux-musl
+          #   aarch64-linux-gnu -> aarch64-linux-musl
+          MUSL_MULTIARCH="${GNU_MULTIARCH%-gnu}-musl"
+
+          # musl-gcc searches this include directory.
+          MUSL_INCLUDE="/usr/include/${MUSL_MULTIARCH}"
+
+          # Linux arch-specific asm headers are installed here by linux-libc-dev.
+          GNU_ASM="/usr/include/${GNU_MULTIARCH}/asm"
+
+          # Ensure the musl include directory exists.
+          sudo mkdir -p "$MUSL_INCLUDE"
+
+          # Remove old paths first.
+          # This avoids silently keeping broken/stale symlinks from previous runs.
+          sudo rm -rf "$MUSL_INCLUDE/linux"
+          sudo rm -rf "$MUSL_INCLUDE/asm"
+          sudo rm -rf "$MUSL_INCLUDE/asm-generic"
+
+          # Expose Linux UAPI headers to musl-gcc.
+          # This fixes packages that include headers like <linux/swab.h>.
+          sudo ln -s /usr/include/linux "$MUSL_INCLUDE/linux"
+
+          # Expose architecture-specific asm headers to musl-gcc.
+          sudo ln -s "$GNU_ASM" "$MUSL_INCLUDE/asm"
+
+          # Expose generic asm headers used by many Linux headers.
+          sudo ln -s /usr/include/asm-generic "$MUSL_INCLUDE/asm-generic"
+
+          # Smoke test: fail early if musl-gcc still cannot find Linux headers.
+          echo '#include <linux/swab.h>' > /tmp/test.c
+          musl-gcc -c /tmp/test.c -o /tmp/test.o
+
       - name: Use OCaml ${{matrix.ocaml_compiler}}
         uses: ocaml/setup-ocaml@v3.6.0
         if: steps.cache-opam-env.outputs.cache-hit != 'true'

dune

@@ -1 +1 @@
-(dirs compiler tests analysis tools)
+(dirs compiler tests analysis tools lsp)

dune-project

@@ -75,3 +75,18 @@
   (yojson
     (= 3.0.0))
   (odoc :with-doc)))
+
+(package
+ (name rescript-language-server)
+ (synopsis "ReScript LSP")
+ (depends
+ (ocaml
+  (>= 4.10))
+ (lsp
+  (>= 1.22.0))
+ (eio
+  (>= 1.3))
+ (eio_main
+  (>= 1.3))
+ analysis
+ dune))

lsp/bin/dune

@@ -0,0 +1,5 @@
+(executable
+ (name main)
+ (package rescript-language-server)
+ (public_name rescript-language-server)
+ (libraries rescript_language_server))

lsp/bin/main.ml

@@ -0,0 +1 @@
+let () = Rescript_language_server.main ()

lsp/src/diagnostics.ml

@@ -0,0 +1,5 @@
+module UriMap = Map.Make (Lsp.Uri)
+
+type t = Lsp.Types.Diagnostic.t list UriMap.t
+
+let create () = UriMap.empty

lsp/src/document_store.ml

@@ -0,0 +1,30 @@
+(* module UriMap = Map.Make (Lsp.Uri) *)
+
+type document = {text: string; version: int}
+
+type t = {documents: (Lsp.Uri.t, document) Hashtbl.t}
+
+let create () = {documents = Hashtbl.create 25}
+
+let open_document t ~uri ~text ~version =
+  Hashtbl.add t.documents uri {text; version};
+  t
+
+let update_document t ~uri ~text ~version =
+  (match Hashtbl.find_opt t.documents uri with
+  | None ->
+    raise
+      (Failure (Printf.sprintf "Document not found: %s" (Lsp.Uri.to_string uri)))
+  | Some _ -> Hashtbl.replace t.documents uri {text; version});
+  t
+
+let remove_document t ~uri =
+  Hashtbl.remove t.documents uri;
+  t
+
+let get_document t ~uri =
+  match Hashtbl.find_opt t.documents uri with
+  | Some doc -> doc
+  | None ->
+    raise
+      (Failure (Printf.sprintf "Document not found: %s" (Lsp.Uri.to_string uri)))

lsp/src/dune

@@ -0,0 +1,5 @@
+(library
+ (name rescript_language_server)
+ (libraries lsp eio eio_main analysis)
+ (flags
+  (-w "-9")))

lsp/src/hover.ml

@@ -0,0 +1,16 @@
+open Lsp.Types
+
+let create ~(position : Position.t) ~(uri : DocumentUri.t)
+    (server : State.t Server.t) =
+  let path = DocumentUri.to_path uri in
+  let pos = (position.line, position.character) in
+
+  (* NOTE: Should be a config *)
+  let supportsMarkdownLinks = true in
+  let debug = false in
+  let open Analysis in
+  let source = (Document_store.get_document ~uri server.state.store).text in
+  let kindFile = Files.classifySourceFile path in
+  let full = Cmt.loadFullCmtFromPath ~path in
+
+  Commands.hover ~source ~kindFile ~pos ~debug ~supportsMarkdownLinks ~full

lsp/src/rescript_language_server.ml

@@ -0,0 +1,79 @@
+let initialization (client_capabilities : Lsp.Types.ClientCapabilities.t) =
+  let open Lsp.Types in
+  let textDocumentSync =
+    `TextDocumentSyncOptions
+      (TextDocumentSyncOptions.create ~openClose:true
+         ~change:TextDocumentSyncKind.Full ~willSave:false
+         ~save:(`SaveOptions (SaveOptions.create ~includeText:false ()))
+         ~willSaveWaitUntil:false ())
+  in
+  let capabilities =
+    ServerCapabilities.create ~textDocumentSync ~hoverProvider:(`Bool true) ()
+  in
+  let serverInfo =
+    let version = "2.0.0-aplha.1" in
+    InitializeResult.create_serverInfo ~name:"rescript-language-server" ~version
+      ()
+  in
+  InitializeResult.create ~capabilities ~serverInfo ()
+
+let on_initialize (params : Lsp.Types.InitializeParams.t) (state : State.t) =
+  (* TODO:
+    * Find root project (rescript.json, package.json) using InitializeParams.workspaceFolders and save in State.t
+      * See https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#initializeParams
+      * If not found rescript.json kill the server?
+    * Save initializationOptions in State.t
+      * This options are: askToStartBuild, codeLens.enable, inlayHints.enable, etc..
+    * Collect compiler diagnostics (syntax and type)?
+  *)
+  let diagnostics = Diagnostics.create () in
+  let initialization_info = initialization params.capabilities in
+  let state = State.initialize state ~params ~diagnostics in
+  (initialization_info, state)
+
+let on_request (Lsp.Client_request.E request) (server : State.t Server.t) =
+  let state = Server.state server in
+  let ok value = Ok (Lsp.Client_request.yojson_of_result request value) in
+  match request with
+  | Lsp.Client_request.Initialize params ->
+    let initialization_info, state = on_initialize params state in
+    (ok initialization_info, state)
+  | Shutdown -> (ok (), state)
+  | TextDocumentHover {position; textDocument = {uri}} ->
+    (ok (Hover.create ~position ~uri server), state)
+  | _ ->
+    let err =
+      Jsonrpc.Response.Error.make
+        ~code:Jsonrpc.Response.Error.Code.MethodNotFound
+        ~message:"Request method not supported" ()
+    in
+    (Error err, state)
+
+let on_notification notification (server : State.t Server.t) =
+  let state = Server.state server in
+
+  match notification with
+  | Lsp.Client_notification.TextDocumentDidOpen
+      {textDocument = {uri; text; version; _}} ->
+    let store = Document_store.open_document ~uri ~text ~version state.store in
+    {state with store}
+  (* | TextDocumentDidChange {textDocument = {uri; version; _}; contentChanges}
+    -> (
+    match List.rev contentChanges with
+    | {text; _} :: _ -> state
+    | [] -> state) *)
+  | TextDocumentDidClose {textDocument = {uri; _}} ->
+    (* TODO:
+     * remove state diagnostics
+     * send updated diagnostics?
+     *)
+    let store = Document_store.remove_document ~uri state.store in
+    {state with store}
+  | Exit -> state
+  | _ -> state
+
+let main () =
+  Eio_main.run (fun env ->
+      let state = State.create ~store:(Document_store.create ()) in
+      Server.listen ~input:env#stdin ~output:env#stdout ~on_request
+        ~on_notification ~state ~env)