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

@@ -221,7 +221,7 @@ let main () =
   | [_; "format"; path] -> Cli.format ~path
   | [_; "test"; path] -> Cli.test ~state ~path
   | [_; "cmt"; rescript_json; cmt_path] ->
-    Cmt_viewer.dump ~state rescript_json cmt_path
+    Cli.dump_cmt ~state ~rescript_json ~cmt_path
   | args when List.mem "-h" args || List.mem "--help" args -> prerr_endline help
   | _ ->
     prerr_endline help;

analysis/src/build_system.ml

@@ -5,39 +5,19 @@ let namespaced_name namespace name =
 
 let ( /+ ) = Filename.concat
 
-(*
-Editor tooling can more accurately resolve the runtime path and will try and pass it via an environment variable.
-Example path: "test-stdlib/node_modules/.pnpm/@rescript+runtime@12.0.0-rc.4/node_modules/@rescript/runtime"
-*)
-
 let get_runtime_dir root_path =
   match !Cfg.is_doc_gen_from_compiler with
   | false -> (
-    (* First check RESCRIPT_RUNTIME environment variable, like bsc does *)
-    match Sys.getenv_opt "RESCRIPT_RUNTIME" with
-    | Some env_path ->
-      if Debug.verbose () then
-        Printf.printf "[getRuntimeDir] Using RESCRIPT_RUNTIME=%s\n" env_path;
-      Some env_path
-    | None -> (
-      let result =
-        Module_resolution.resolve_node_module_path ~start_path:root_path
-          "@rescript/runtime"
-      in
-      match result with
-      | Some path ->
-        if Debug.verbose () then
-          Printf.printf "[getRuntimeDir] Resolved via node_modules: %s\n" path;
-        Some path
-      | None ->
-        let message = "@rescript/runtime could not be found" in
-        Log.log message;
-        if Debug.verbose () then
-          Printf.printf
-            "[getRuntimeDir] Failed to resolve @rescript/runtime from \
-             rootPath=%s\n"
-            root_path;
-        None))
+    let result =
+      Module_resolution.resolve_node_module_path ~start_path:root_path
+        "@rescript/runtime"
+    in
+    match result with
+    | Some path -> Some path
+    | None ->
+      let message = "@rescript/runtime could not be found" in
+      Log.log message;
+      None)
   | true -> Some root_path
 
 let get_lib_bs path = Files.if_exists (path /+ "lib" /+ "bs")

analysis/src/cli.ml

@@ -182,6 +182,25 @@ let create_interface ~path ~cmi_file =
   in
   Printf.printf "%s" result
 
+let dump_cmt ~state ~rescript_json ~cmt_path =
+  let uri = Uri.from_path (Filename.remove_extension cmt_path ^ ".res") in
+  let package =
+    let uri = Uri.from_path rescript_json in
+    Packages.get_package ~state ~uri
+  in
+  match package with
+  | None -> print_null ()
+  | Some package -> (
+    let module_name =
+      Build_system.namespaced_name package.namespace
+        (Find_files.get_name cmt_path)
+    in
+    match Cmt.full_for_cmt ~module_name ~package ~uri cmt_path with
+    | None -> print_null ()
+    | Some full ->
+      let content = Cmt_viewer.dump ~full ~filter_for_position:None in
+      Printf.printf "%s" content)
+
 let test ~state ~path =
   Uri.strip_path := true;
   match Files.read_file path with