service/dap: support pause request

service/dap/daptest/client.go

@@ -284,9 +284,9 @@ func (c *Client) StepOutRequest(thread int) {
 }
 
 // PauseRequest sends a 'pause' request.
-func (c *Client) PauseRequest() {
-	request := &dap.NextRequest{Request: *c.newRequest("pause")}
-	// TODO(polina): arguments
+func (c *Client) PauseRequest(threadId int) {
+	request := &dap.PauseRequest{Request: *c.newRequest("pause")}
+	request.Arguments.ThreadId = threadId
 	c.send(request)
 }
 

service/dap/error_ids.go

@@ -21,6 +21,7 @@ const (
 	UnableToListGlobals        = 2007
 	UnableToLookupVariable     = 2008
 	UnableToEvaluateExpression = 2009
+	UnableToHalt               = 2010
 
 	DebuggeeIsRunning = 4000
 	DisconnectError   = 5000

service/dap/server.go

@@ -360,15 +360,14 @@ func (s *Server) handleRequest(request dap.Message) {
 		return
 	}
 
-	// These requests, can be handeled regardless of whether the targret is running
+	// These requests, can be handled regardless of whether the targret is running
 	switch request := request.(type) {
 	case *dap.DisconnectRequest:
 		// Required
 		s.onDisconnectRequest(request)
 		return
 	case *dap.PauseRequest:
 		// Required
-		// TODO: implement this request in V0
 		s.onPauseRequest(request)
 		return
 	case *dap.TerminateRequest:
@@ -1220,10 +1219,20 @@ func (s *Server) doStepCommand(command string, threadId int, asyncSetupDone chan
 	s.doCommand(command, asyncSetupDone)
 }
 
-// onPauseRequest sends a not-yet-implemented error response.
+// onPauseRequest handles 'pause' request.
 // This is a mandatory request to support.
-func (s *Server) onPauseRequest(request *dap.PauseRequest) { // TODO V0
-	s.sendNotYetImplementedErrorResponse(request.Request)
+func (s *Server) onPauseRequest(request *dap.PauseRequest) {
+	_, err := s.debugger.Command(&api.DebuggerCommand{Name: api.Halt}, nil)
+	if err != nil {
+		s.sendErrorResponse(request.Request, UnableToHalt, "Unable to halt execution", err.Error())
+		return
+	}
+	s.send(&dap.PauseResponse{Response: *newResponse(request.Request)})
+	// No need to send any event here.
+	// If we received this request while stopped, there already was an event for the stop.
+	// If we received this while running, then doCommand will unblock and trigger the right
+	// event, using debugger.StopReason because manual stop reason always wins even if we
+	// simultaneously receive a manual stop request and hit a breakpoint.
 }
 
 // stackFrame represents the index of a frame within
@@ -1912,7 +1921,7 @@ func (s *Server) resetHandlesForStoppedEvent() {
 // asynchornous command has completed setup or was interrupted
 // due to an error, so the server is ready to receive new requests.
 func (s *Server) doCommand(command string, asyncSetupDone chan struct{}) {
-	// TODO(polina): it appears that debugger.Command doesn't close
+	// TODO(polina): it appears that debugger.Command doesn't always close
 	// asyncSetupDone (e.g. when having an error next while nexting).
 	// So we should always close it ourselves just in case.
 	defer s.asyncCommandDone(asyncSetupDone)
@@ -1929,14 +1938,18 @@ func (s *Server) doCommand(command string, asyncSetupDone chan struct{}) {
 	if err == nil {
 		stopped.Body.ThreadId = stoppedGoroutineID(state)
 
+		file, line := "?", -1
+		if state.CurrentThread != nil {
+			file, line = state.CurrentThread.File, state.CurrentThread.Line
+		}
 		sr := s.debugger.StopReason()
-		s.log.Debugf("%q command stopped - reason %q", command, sr)
+		s.log.Debugf("%q command stopped - reason %q, location %s:%d", command, sr, file, line)
 		switch sr {
 		case proc.StopNextFinished:
 			stopped.Body.Reason = "step"
 		case proc.StopManual: // triggered by halt
 			stopped.Body.Reason = "pause"
-		case proc.StopUnknown: // can happen while stopping
+		case proc.StopUnknown: // can happen while terminating
 			stopped.Body.Reason = "unknown"
 		case proc.StopWatchpoint:
 			stopped.Body.Reason = "data breakpoint"

service/dap/server_test.go

@@ -582,6 +582,20 @@ func TestPreSetBreakpoint(t *testing.T) {
 		// "Continue" is triggered after the response is sent
 
 		client.ExpectTerminatedEvent(t)
+
+		// Pause request after termination should result in an error.
+		// But in certain cases this request actually succeeds.
+		client.PauseRequest(1)
+		switch r := client.ExpectMessage(t).(type) {
+		case *dap.ErrorResponse:
+			if r.Message != "Unable to halt execution" {
+				t.Errorf("\ngot  %#v\nwant Message='Unable to halt execution'", r)
+			}
+		case *dap.PauseResponse:
+		default:
+			t.Fatalf("Unexpected response type: expect error or pause, got %#v", r)
+		}
+
 		client.DisconnectRequest()
 		client.ExpectOutputEventProcessExited(t, 0)
 		client.ExpectOutputEventDetaching(t)
@@ -2666,15 +2680,8 @@ func TestFatalThrowBreakpoint(t *testing.T) {
 	})
 }
 
-// handleStop covers the standard sequence of reqeusts issued by
-// a client at a breakpoint or another non-terminal stop event.
-// The details have been tested by other tests,
-// so this is just a sanity check.
-// Skips line check if line is -1.
-func handleStop(t *testing.T, client *daptest.Client, thread int, name string, line int) {
+func verifyStopLocation(t *testing.T, client *daptest.Client, thread int, name string, line int) {
 	t.Helper()
-	client.ThreadsRequest()
-	client.ExpectThreadsResponse(t)
 
 	client.StackTraceRequest(thread, 0, 20)
 	st := client.ExpectStackTraceResponse(t)
@@ -2688,6 +2695,19 @@ func handleStop(t *testing.T, client *daptest.Client, thread int, name string, l
 			t.Errorf("\ngot  %#v\nwant Name=%q", st, name)
 		}
 	}
+}
+
+// handleStop covers the standard sequence of requests issued by
+// a client at a breakpoint or another non-terminal stop event.
+// The details have been tested by other tests,
+// so this is just a sanity check.
+// Skips line check if line is -1.
+func handleStop(t *testing.T, client *daptest.Client, thread int, name string, line int) {
+	t.Helper()
+	client.ThreadsRequest()
+	client.ExpectThreadsResponse(t)
+
+	verifyStopLocation(t, client, thread, name, line)
 
 	client.ScopesRequest(1000)
 	client.ExpectScopesResponse(t)
@@ -2985,6 +3005,51 @@ func TestAttachRequest(t *testing.T) {
 	})
 }
 
+func TestPauseAndContinue(t *testing.T) {
+	runTest(t, "loopprog", func(client *daptest.Client, fixture protest.Fixture) {
+		runDebugSessionWithBPs(t, client, "launch",
+			// Launch
+			func() {
+				client.LaunchRequest("exec", fixture.Path, !stopOnEntry)
+			},
+			// Set breakpoints
+			fixture.Source, []int{6},
+			[]onBreakpoint{{
+				execute: func() {
+					verifyStopLocation(t, client, 1, "main.loop", 6)
+
+					// Continue resumes all goroutines, so thread id is ignored
+					client.ContinueRequest(12345)
+					client.ExpectContinueResponse(t)
+
+					time.Sleep(time.Second)
+
+					// Halt pauses all goroutines, so thread id is ignored
+					client.PauseRequest(56789)
+					// Since we are in async mode while running, we might receive next two messages in either order.
+					for i := 0; i < 2; i++ {
+						msg := client.ExpectMessage(t)
+						switch m := msg.(type) {
+						case *dap.StoppedEvent:
+							if m.Body.Reason != "pause" || m.Body.ThreadId != 0 && m.Body.ThreadId != 1 {
+								t.Errorf("\ngot %#v\nwant ThreadId=0/1 Reason='pause'", m)
+							}
+						case *dap.PauseResponse:
+						default:
+							t.Fatalf("got %#v, want StoppedEvent or PauseResponse", m)
+						}
+					}
+
+					// Pause will be a no-op at a pause: there will be no additional stopped events
+					client.PauseRequest(1)
+					client.ExpectPauseResponse(t)
+				},
+				// The program has an infinite loop, so we must kill it by disconnecting.
+				disconnect: true,
+			}})
+	})
+}
+
 func TestUnupportedCommandResponses(t *testing.T) {
 	var got *dap.ErrorResponse
 	runTest(t, "increment", func(client *daptest.Client, fixture protest.Fixture) {
@@ -3036,24 +3101,6 @@ func TestUnupportedCommandResponses(t *testing.T) {
 	})
 }
 
-func TestRequiredNotYetImplementedResponses(t *testing.T) {
-	var got *dap.ErrorResponse
-	runTest(t, "increment", func(client *daptest.Client, fixture protest.Fixture) {
-		seqCnt := 1
-		expectNotYetImplemented := func(cmd string) {
-			t.Helper()
-			got = client.ExpectNotYetImplementedErrorResponse(t)
-			if got.RequestSeq != seqCnt || got.Command != cmd {
-				t.Errorf("\ngot  %#v\nwant RequestSeq=%d Command=%s", got, seqCnt, cmd)
-			}
-			seqCnt++
-		}
-
-		client.PauseRequest()
-		expectNotYetImplemented("pause")
-	})
-}
-
 func TestOptionalNotYetImplementedResponses(t *testing.T) {
 	var got *dap.ErrorResponse
 	runTest(t, "increment", func(client *daptest.Client, fixture protest.Fixture) {