service/dap: do not send a halt request if the debuggee is not running (#2686)

updates go-delve/delve#2685

service/dap/server.go

@@ -1568,10 +1568,12 @@ func (s *Server) doStepCommand(command string, threadId int, asyncSetupDone chan
 // onPauseRequest handles 'pause' request.
 // This is a mandatory request to support.
 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
+	if s.debugger.IsRunning() {
+		_, 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.

service/dap/server_test.go

@@ -2296,6 +2296,64 @@ func TestSetBreakpoint(t *testing.T) {
 	})
 }
 
+func TestPauseAtStop(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{16},
+			[]onBreakpoint{{
+				execute: func() {
+					checkStop(t, client, 1, "main.main", 16)
+
+					client.SetBreakpointsRequest(fixture.Source, []int{6, 8})
+					expectSetBreakpointsResponse(t, client, []Breakpoint{{6, fixture.Source, true, ""}, {8, fixture.Source, true, ""}})
+
+					// Send a pause request while stopped on a cleared breakpoint.
+					client.PauseRequest(1)
+					client.ExpectPauseResponse(t)
+
+					client.ContinueRequest(1)
+					client.ExpectContinueResponse(t)
+					client.ExpectStoppedEvent(t)
+					checkStop(t, client, 1, "main.loop", 6)
+
+					// Send a pause request while stopped on a breakpoint.
+					client.PauseRequest(1)
+					client.ExpectPauseResponse(t)
+
+					client.ContinueRequest(1)
+					client.ExpectContinueResponse(t)
+					se := client.ExpectStoppedEvent(t)
+					if se.Body.Reason != "breakpoint" {
+						t.Errorf("got %#v, expected breakpoint", se)
+					}
+					checkStop(t, client, 1, "main.loop", 8)
+
+					// Send a pause request while stopped after stepping.
+					client.NextRequest(1)
+					client.ExpectNextResponse(t)
+					client.ExpectStoppedEvent(t)
+					checkStop(t, client, 1, "main.loop", 9)
+
+					client.PauseRequest(1)
+					client.ExpectPauseResponse(t)
+
+					client.ContinueRequest(1)
+					client.ExpectContinueResponse(t)
+
+					client.ExpectStoppedEvent(t)
+					checkStop(t, client, 1, "main.loop", 8)
+				},
+				// The program has an infinite loop, so we must kill it by disconnecting.
+				disconnect: true,
+			}})
+	})
+}
+
 func checkHitBreakpointIds(t *testing.T, se *dap.StoppedEvent, reason string, id int) {
 	if se.Body.ThreadId != 1 || se.Body.Reason != reason || len(se.Body.HitBreakpointIds) != 1 || se.Body.HitBreakpointIds[0] != id {
 		t.Errorf("got %#v, want Reason=%q, ThreadId=1, HitBreakpointIds=[]int{%d}", se, reason, id)