service/dap: send continued event before step response (go-delve#2594)

* service/dap: send continued event before step response

Send the continued event before the step response to make sure that there is no time where the client believes that only a single thread is running.

Updates golang/vscode-go#1617

* move to helper

service/dap/server.go

@@ -1510,24 +1510,37 @@ func (s *Server) onAttachRequest(request *dap.AttachRequest) {
 // onNextRequest handles 'next' request.
 // This is a mandatory request to support.
 func (s *Server) onNextRequest(request *dap.NextRequest, asyncSetupDone chan struct{}) {
-	s.send(&dap.NextResponse{Response: *newResponse(request.Request)})
+	s.sendStepResponse(request.Arguments.ThreadId, &dap.NextResponse{Response: *newResponse(request.Request)})
 	s.doStepCommand(api.Next, request.Arguments.ThreadId, asyncSetupDone)
 }
 
 // onStepInRequest handles 'stepIn' request
 // This is a mandatory request to support.
 func (s *Server) onStepInRequest(request *dap.StepInRequest, asyncSetupDone chan struct{}) {
-	s.send(&dap.StepInResponse{Response: *newResponse(request.Request)})
+	s.sendStepResponse(request.Arguments.ThreadId, &dap.StepInResponse{Response: *newResponse(request.Request)})
 	s.doStepCommand(api.Step, request.Arguments.ThreadId, asyncSetupDone)
 }
 
 // onStepOutRequest handles 'stepOut' request
 // This is a mandatory request to support.
 func (s *Server) onStepOutRequest(request *dap.StepOutRequest, asyncSetupDone chan struct{}) {
-	s.send(&dap.StepOutResponse{Response: *newResponse(request.Request)})
+	s.sendStepResponse(request.Arguments.ThreadId, &dap.StepOutResponse{Response: *newResponse(request.Request)})
 	s.doStepCommand(api.StepOut, request.Arguments.ThreadId, asyncSetupDone)
 }
 
+func (s *Server) sendStepResponse(threadId int, message dap.Message) {
+	// All of the threads will be continued by this request, so we need to send
+	// a continued event so the UI can properly reflect the current state.
+	s.send(&dap.ContinuedEvent{
+		Event: *newEvent("continued"),
+		Body: dap.ContinuedEventBody{
+			ThreadId:            threadId,
+			AllThreadsContinued: true,
+		},
+	})
+	s.send(message)
+}
+
 func stoppedGoroutineID(state *api.DebuggerState) (id int) {
 	if state.SelectedGoroutine != nil {
 		id = state.SelectedGoroutine.ID
@@ -1544,15 +1557,6 @@ func stoppedGoroutineID(state *api.DebuggerState) (id int) {
 // due to an error, so the server is ready to receive new requests.
 func (s *Server) doStepCommand(command string, threadId int, asyncSetupDone chan struct{}) {
 	defer s.asyncCommandDone(asyncSetupDone)
-	// All of the threads will be continued by this request, so we need to send
-	// a continued event so the UI can properly reflect the current state.
-	s.send(&dap.ContinuedEvent{
-		Event: *newEvent("continued"),
-		Body: dap.ContinuedEventBody{
-			ThreadId:            threadId,
-			AllThreadsContinued: true,
-		},
-	})
 	_, err := s.debugger.Command(&api.DebuggerCommand{Name: api.SwitchGoroutine, GoroutineID: threadId}, nil)
 	if err != nil {
 		s.log.Errorf("Error switching goroutines while stepping: %v", err)