feat: publish the Hime-san Beta 2 LSP

Add the standard-library language server, editor-neutral protocol contract, additive version feature discovery, and bounded security regressions while leaving the Sando runtime unchanged. Material design and implementation assistance was provided by OpenAI Codex.

Signed-off-by: Cole Speelman <crspeelman@gmail.com>

cmd/himesan/main.go

@@ -18,6 +18,7 @@ import (
 
 	"gamertan.com/sandwich-hime/internal/compiler"
 	"gamertan.com/sandwich-hime/internal/devserver"
+	"gamertan.com/sandwich-hime/internal/lsp"
 	"gamertan.com/sandwich-hime/internal/version"
 )
 
@@ -38,6 +39,8 @@ func run(ctx context.Context, args []string, stdout, stderr io.Writer) int {
 		return runCompilerCommand(ctx, args[0], args[1:], stdout, stderr, compiler.Check)
 	case "dev":
 		return runDev(ctx, args[1:], stdout, stderr)
+	case "lsp":
+		return runLSP(ctx, args[1:], os.Stdin, stdout, stderr)
 	case "version":
 		return runVersion(args[1:], stdout, stderr)
 	case "help", "-h", "--help":
@@ -116,10 +119,11 @@ func runVersion(args []string, stdout, stderr io.Writer) int {
 		return 2
 	}
 	information := struct {
-		Compiler   string `json:"compiler"`
-		RuntimeABI string `json:"runtime_abi"`
-		Go         string `json:"go"`
-	}{Compiler: version.Compiler, RuntimeABI: version.RuntimeABI, Go: runtime.Version()}
+		Compiler   string   `json:"compiler"`
+		RuntimeABI string   `json:"runtime_abi"`
+		Go         string   `json:"go"`
+		Features   []string `json:"features"`
+	}{Compiler: version.Compiler, RuntimeABI: version.RuntimeABI, Go: runtime.Version(), Features: []string{"lsp-stdio"}}
 	if *jsonOutput {
 		if err := json.NewEncoder(stdout).Encode(information); err != nil {
 			fmt.Fprintf(stderr, "himesan: encode version: %v\n", err)
@@ -131,6 +135,27 @@ func runVersion(args []string, stdout, stderr io.Writer) int {
 	return 0
 }
 
+func runLSP(ctx context.Context, args []string, stdin io.Reader, stdout, stderr io.Writer) int {
+	flags := flag.NewFlagSet("lsp", flag.ContinueOnError)
+	flags.SetOutput(stderr)
+	stdio := flags.Bool("stdio", false, "serve Language Server Protocol JSON-RPC over stdin/stdout")
+	if err := flags.Parse(args); err != nil {
+		if errors.Is(err, flag.ErrHelp) {
+			return 0
+		}
+		return 2
+	}
+	if !*stdio || flags.NArg() != 0 {
+		fmt.Fprintln(stderr, "himesan lsp requires exactly --stdio")
+		return 2
+	}
+	if err := lsp.Run(ctx, lsp.Options{Input: stdin, Output: stdout, LogOutput: stderr}); err != nil {
+		fmt.Fprintf(stderr, "himesan lsp: %v\n", err)
+		return 1
+	}
+	return 0
+}
+
 type stringList []string
 
 func (values *stringList) String() string { return strings.Join(*values, ",") }
@@ -312,6 +337,7 @@ func printHelp(output io.Writer) {
 	fmt.Fprintln(output, "  himesan check [--json] [paths...]     validate sources and committed output without writes")
 	fmt.Fprintln(output, "  himesan bless [--json] [paths...]     friendly read-only alias for check")
 	fmt.Fprintln(output, "  himesan dev [flags] [package] [-- app-args...]  run the loopback last-good supervisor")
+	fmt.Fprintln(output, "  himesan lsp --stdio                  run the read-only language server")
 	fmt.Fprintln(output, "  himesan version [--json]              print compiler and runtime ABI versions")
 	fmt.Fprintln(output)
 	fmt.Fprintln(output, "Templates use .sando; .san remains exclusively San language source.")

cmd/himesan/main_test.go

@@ -30,14 +30,24 @@ func TestRunHelpVersionAndUnknownCommand(t *testing.T) {
 	if code := run(context.Background(), []string{"version", "--json"}, &stdout, &stderr); code != 0 {
 		t.Fatalf("version exit code = %d: %s", code, stderr.String())
 	}
-	var versionResult map[string]string
+	var versionResult struct {
+		Compiler   string   `json:"compiler"`
+		RuntimeABI string   `json:"runtime_abi"`
+		Features   []string `json:"features"`
+	}
 	if err := json.Unmarshal(stdout.Bytes(), &versionResult); err != nil {
 		t.Fatalf("version JSON: %v", err)
 	}
-	if versionResult["compiler"] == "" || versionResult["runtime_abi"] != compiler.RuntimeABI {
+	if versionResult.Compiler == "" || versionResult.RuntimeABI != compiler.RuntimeABI || len(versionResult.Features) != 1 || versionResult.Features[0] != "lsp-stdio" {
 		t.Fatalf("version result = %#v", versionResult)
 	}
 
+	stdout.Reset()
+	stderr.Reset()
+	if code := run(context.Background(), []string{"lsp"}, &stdout, &stderr); code != 2 {
+		t.Fatalf("lsp without --stdio exit code = %d, want 2", code)
+	}
+
 	stdout.Reset()
 	stderr.Reset()
 	if code := run(context.Background(), []string{"rebuke"}, &stdout, &stderr); code != 2 {