⚡ Optimize grpcWriteStatus to avoid unnecessary allocation

private/server/handler.go

@@ -301,7 +301,13 @@ func NewHandler(service protoreflect.ServiceDescriptor, faker fauxrpc.ProtoFaker
 func grpcWriteStatus(w http.ResponseWriter, st *status.Status) {
 	w.Header().Set("Grpc-Status", strconv.FormatInt(int64(st.Code()), 10))
 	w.Header().Set("Grpc-Message", st.Message())
-	if details, err := proto.Marshal(st.Proto()); err != nil {
+
+	p := st.Proto()
+	if len(p.Details) == 0 {
+		return
+	}
+
+	if details, err := proto.Marshal(p); err != nil {
 		slog.Error("error serializing validation details", "error", err)
 	} else {
 		w.Header().Set("Grpc-Status-Details-Bin", base64.StdEncoding.EncodeToString(details))

private/server/handler_bench_test.go

@@ -3,6 +3,7 @@ package server
 import (
 	"bytes"
 	"encoding/binary"
+	"net/http"
 	"net/http/httptest"
 	"testing"
 
@@ -12,6 +13,8 @@ import (
 	"github.com/sudorandom/fauxrpc"
 	fauxlog "github.com/sudorandom/fauxrpc/private/log"
 	"github.com/sudorandom/fauxrpc/private/stubs"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 	"google.golang.org/protobuf/proto"
 )
 
@@ -64,3 +67,33 @@ func BenchmarkHandler_RequestAllocation(b *testing.B) {
 		handler.ServeHTTP(w, req)
 	}
 }
+
+type mockWriter struct {
+	h http.Header
+}
+
+func (m *mockWriter) Header() http.Header {
+	return m.h
+}
+
+func (m *mockWriter) Write([]byte) (int, error) {
+	return 0, nil
+}
+
+func (m *mockWriter) WriteHeader(statusCode int) {}
+
+func BenchmarkGRPCWriteStatus(b *testing.B) {
+	st := status.New(codes.NotFound, "not found")
+	w := &mockWriter{h: make(http.Header)}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+
+	for i := 0; i < b.N; i++ {
+		grpcWriteStatus(w, st)
+		// Reset header
+		for k := range w.h {
+			delete(w.h, k)
+		}
+	}
+}