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'
@@ -326,6 +377,11 @@ jobs:
         if: runner.os != 'Windows'
         run: make -C tests/gentype_tests/typescript-react-example clean test
 
+      # The Makefile skip some tests on Windows because OCaml Eio process operations is not supported on Windows yet
+      # Eio.Stdenv.process_mgr raise a error, see https://github.com/ocaml-multicore/eio/blob/37d6e67f7e25b43e4a66574ed98838c79f1a21b4/lib_eio_windows/eio_windows.ml#L36
+      - name: Run LSP tests
+        run: opam exec -- make test-lsp
+
       # On Windows, after running setup-ocaml (if it wasn't cached yet or the cache couldn't be restored),
       # Cygwin bash is used instead of Git Bash for Windows, breaking the rewatch tests.
       # So we need to adjust the path to bring back Git Bash for Windows.
@@ -604,7 +660,7 @@ jobs:
         uses: actions/checkout@v6
       - name: Run make in dev container
         uses: devcontainers/ci@v0.3
-        with:    
+        with:
           push: never
           runCmd: make
 

Makefile

@@ -176,7 +176,25 @@ test-gentype: lib
 test-rewatch: lib
 	./rewatch/tests/suite.sh $(RESCRIPT_EXE)
 
-test-all: test test-gentype test-analysis test-tools test-rewatch
+test-lsp: lib
+	@for dir in tests/lsp_tests/*-workspace/; do \
+			[ -d "$$dir" ] || continue; \
+			echo "Building $${dir%/}..."; \
+			( cd "$$dir" && yarn clean && yarn build ); \
+	done
+	@dune runtest
+	@if [ "$$OS" = "Windows_NT" ]; then \
+		echo "Skipping lsp-tests executable on Windows"; \
+	else \
+		dune exec -- lsp-tests; \
+	fi
+	@if [ -n "$$(git ls-files --modified tests/lsp_tests/**/*.expected)" ]; then \
+    	echo "The lsp_tests snapshot doesn't match. Double check that the output is correct, run 'make test-lsp' and stage the diff"; \
+    	git --no-pager diff tests/lsp_tests/**/*.expected; \
+    	exit 1; \
+    fi \
+
+test-all: test test-gentype test-analysis test-tools test-rewatch test-lsp
 
 # Playground
 

analysis/bin/main.ml

@@ -148,7 +148,7 @@ let main () =
     Cli.type_definition ~state ~path
       ~pos:(int_of_string line, int_of_string col)
       ~debug
-  | [_; "documentSymbol"; path] -> Document_symbol.command ~path
+  | [_; "documentSymbol"; path] -> Cli.document_symbol ~path
   | [_; "hover"; path; line; col; current_file; supports_markdown_links] ->
     Cli.hover ~state ~path
       ~pos:(int_of_string line, int_of_string col)

analysis/src/cli.ml

@@ -161,6 +161,15 @@ let semantic_tokens ~path =
     let tokens = Semantic_tokens.semantic_tokens ~source ~kind_file in
     Lsp.Types.SemanticTokens.yojson_of_t tokens |> print_string
 
+let document_symbol ~path =
+  match Files.read_file path with
+  | None -> print_null ()
+  | Some source ->
+    let kind_file = Files.classify_source_file path in
+    Document_symbol.get_symbols ~source ~kind_file
+    |> List.map Lsp.Types.DocumentSymbol.yojson_of_t
+    |> print_list
+
 let test ~state ~path =
   Uri.strip_path := true;
   match Files.read_file path with
@@ -247,7 +256,7 @@ let test ~state ~path =
             Dce_command.command ()
           | "doc" ->
             print_endline ("DocumentSymbol " ^ path);
-            Document_symbol.command ~path
+            document_symbol ~path
           | "hig" ->
             print_endline ("Highlight " ^ path);
             let source = Files.read_file path |> Option.get in

analysis/src/document_symbol.ml

@@ -1,6 +1,6 @@
 (* https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_documentSymbol *)
 
-let command ~path =
+let get_symbols ~source ~kind_file =
   let symbols = ref [] in
   let add_symbol name loc kind =
     if
@@ -115,17 +115,18 @@ let command ~path =
     }
   in
 
-  (if Filename.check_suffix path ".res" then
+  (if kind_file = Files.Res then
      let parser =
-       Res_driver.parsing_engine.parse_implementation ~for_printer:false
+       Res_driver.parsing_engine.parse_implementation_from_source
+         ~for_printer:false
      in
-     let {Res_driver.parsetree = structure} = parser ~filename:path in
+     let {Res_driver.parsetree = structure} = parser ~source in
      iterator.structure iterator structure |> ignore
    else
      let parser =
-       Res_driver.parsing_engine.parse_interface ~for_printer:false
+       Res_driver.parsing_engine.parse_interface_from_source ~for_printer:false
      in
-     let {Res_driver.parsetree = signature} = parser ~filename:path in
+     let {Res_driver.parsetree = signature} = parser ~source in
      iterator.signature iterator signature |> ignore);
   let is_inside
       ({
@@ -182,9 +183,4 @@ let command ~path =
       |> add_sorted_symbols_to_children ~sorted_symbols:rest
   in
   let sorted_symbols = !symbols |> List.sort compare_symbol in
-  let symbols_with_children =
-    [] |> add_sorted_symbols_to_children ~sorted_symbols
-  in
-  `List (symbols_with_children |> List.map Lsp.Types.DocumentSymbol.yojson_of_t)
-  |> Yojson.Safe.pretty_to_string ~std:true
-  |> print_endline
+  [] |> add_sorted_symbols_to_children ~sorted_symbols

analysis/src/shared_types.ml

@@ -965,3 +965,106 @@ let extract_exp_apply_args ~args =
     | [] -> List.rev acc
   in
   args |> process_args ~acc:[]
+
+let state_to_yojson (state : state) =
+  let option_to_yojson f = function
+    | None -> `Null
+    | Some value -> f value
+  in
+
+  let string_set_to_yojson set =
+    `List (set |> File_set.elements |> List.map (fun value -> `String value))
+  in
+
+  let path_to_yojson path = `List (List.map (fun item -> `String item) path) in
+
+  let paths_to_yojson = function
+    | Impl {cmt; res} ->
+      `Assoc
+        [("kind", `String "Impl"); ("cmt", `String cmt); ("res", `String res)]
+    | Namespace {cmt} ->
+      `Assoc [("kind", `String "Namespace"); ("cmt", `String cmt)]
+    | IntfAndImpl {cmti; resi; cmt; res} ->
+      `Assoc
+        [
+          ("kind", `String "IntfAndImpl");
+          ("cmti", `String cmti);
+          ("resi", `String resi);
+          ("cmt", `String cmt);
+          ("res", `String res);
+        ]
+  in
+
+  let paths_for_module_to_yojson paths_for_module =
+    paths_for_module |> Hashtbl.to_seq
+    |> Seq.map (fun (file, paths) -> (file, paths_to_yojson paths))
+    |> List.of_seq
+    |> fun fields -> `Assoc fields
+  in
+
+  let autocomplete_to_yojson autocomplete =
+    autocomplete |> Misc.String_map.bindings
+    |> List.map (fun (name, files) ->
+           (name, `List (List.map (fun file -> `String file) files)))
+    |> fun fields -> `Assoc fields
+  in
+
+  let package_to_yojson (package : package) =
+    let major, minor = package.rescript_version in
+    `Assoc
+      [
+        ( "generic_jsx_module",
+          option_to_yojson
+            (fun value -> `String value)
+            package.generic_jsx_module );
+        ("suffix", `String package.suffix);
+        ("root_path", `String package.root_path);
+        ("project_files", string_set_to_yojson package.project_files);
+        ("dependencies_files", string_set_to_yojson package.dependencies_files);
+        ("paths_for_module", paths_for_module_to_yojson package.paths_for_module);
+        ( "namespace",
+          option_to_yojson (fun value -> `String value) package.namespace );
+        ("opens", `List (List.map path_to_yojson package.opens));
+        ( "rescript_version",
+          `Assoc [("major", `Int major); ("minor", `Int minor)] );
+        ("autocomplete", autocomplete_to_yojson package.autocomplete);
+      ]
+  in
+
+  let file_to_yojson (file : File.t) =
+    `Assoc
+      [
+        ("uri", `String (file.uri |> Lsp.Uri.to_string));
+        ("module_name", `String file.module_name);
+        ("stamps_count", `Int (List.length (Stamps.get_entries file.stamps)));
+        ("structure_name", `String file.structure.name);
+        ( "structure_docstring",
+          `List (List.map (fun value -> `String value) file.structure.docstring)
+        );
+        ("structure_items_count", `Int (List.length file.structure.items));
+      ]
+  in
+
+  let cmt_cache =
+    state.cmt_cache |> Hashtbl.to_seq
+    |> Seq.map (fun (file_path, file) -> (file_path, file_to_yojson file))
+    |> List.of_seq
+  in
+
+  let root_for_uri =
+    state.root_for_uri |> Hashtbl.to_seq |> List.of_seq
+    |> List.map (fun (uri, str) -> [(Lsp.Uri.to_string uri, `String str)])
+    |> List.flatten
+  in
+
+  let packages_by_root =
+    state.packages_by_root |> Hashtbl.to_seq |> List.of_seq
+    |> List.map (fun (root, package) -> (root, package_to_yojson package))
+  in
+
+  `Assoc
+    [
+      ("cmt_cache", `Assoc cmt_cache);
+      ("root_for_uri", `Assoc root_for_uri);
+      ("packages_by_root", `Assoc packages_by_root);
+    ]

dune

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

dune-project

@@ -75,3 +75,20 @@
   (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
+ (ppx_expect
+  (and :with-test (= v0.17.2)))))

lsp/bin/dune

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

lsp/bin/main.ml

@@ -0,0 +1,6 @@
+let () =
+  Eio_main.run (fun env ->
+      let fs = Eio.Stdenv.fs env in
+      let stdin = Eio.Stdenv.stdin env in
+      let stdout = Eio.Stdenv.stdout env in
+      Rescript_language_server.listen ~input:stdin ~output:stdout ~fs)

lsp/src/compiler.ml

@@ -0,0 +1,29 @@
+module Uri_map = Map.Make (Lsp.Uri)
+
+let collect_diagnostics_from_log_file path =
+  let content = Eio.Path.load path in
+  Compiler_log.Parse.parse_log_content content
+
+let collect_diagnostics_from_log_using_source_dirs workspace_root
+    (state : State.t) =
+  let ( // ) = Filename.concat in
+  let ( /// ) = Eio.Path.( / ) in
+  let workspace_root_path = workspace_root |> Lsp.Types.DocumentUri.to_path in
+  let path =
+    workspace_root_path // Constants.compiler_dir_partial_path
+    // Constants.sources_dirs
+  in
+  let build_roots = Source_dirs.get_build_roots_from_file (state.fs /// path) in
+  let diagnostics =
+    match build_roots with
+    | Some build_roots ->
+      build_roots
+      |> List.map (fun build_root ->
+             let compiler_log_path =
+               workspace_root_path // build_root // Constants.compiler_log
+             in
+             collect_diagnostics_from_log_file (state.fs /// compiler_log_path))
+      |> List.flatten
+    | None -> []
+  in
+  diagnostics