log error in notification handling

Author: Gabriela Araujo Britto

internal/lsp/server.go

@@ -509,9 +509,10 @@ func (s *Server) sendResult(id *jsonrpc.ID, result any) error {
 }
 
 func (s *Server) sendError(id *jsonrpc.ID, err error) error {
-	// Do not send errors for notifications,
+	// Do not send error response for notifications,
 	// except for parse errors which may occur before determining if the message is a request or notification.
 	if id == nil && !errors.Is(err, lsproto.ErrorCodeInvalidRequest) {
+		s.logger.Errorf("error handling notification: %s", err)
 		return nil
 	}
 	code := lsproto.ErrorCodeInternalError

internal/lsp/server_test.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"strings"
 	"sync"
 	"testing"
 
@@ -180,11 +181,12 @@ func TestServerInvalidNotificationParams(t *testing.T) {
 
 	reader := ToReader(io.NopCloser(bytes.NewReader([]byte(rawMessage))))
 	writer := &collectingWriter{}
+	stderr := &strings.Builder{}
 
 	server := NewServer(&ServerOptions{
 		In:  reader,
 		Out: writer,
-		Err: io.Discard,
+		Err: stderr,
 		Cwd: "/test",
 	})
 
@@ -208,4 +210,7 @@ func TestServerInvalidNotificationParams(t *testing.T) {
 		}
 	}
 	assert.Assert(t, !foundError, "expected no error response for invalid notification")
+	errstr := stderr.String()
+	assert.Assert(t, strings.Contains(errstr, "error handling notification"),
+		"expected error log to contain 'error handling notification', got %q", errstr)
 }