Only subscribe to clock topic if ROS time is active

rclpy/rclpy/time_source.py

@@ -40,6 +40,7 @@ def ros_time_is_active(self, enabled):
         self._ros_time_is_active = enabled
         for clock in self._associated_clocks:
             clock._set_ros_time_is_active(True)
+        self._subscribe_to_clock_topic()
 
     def _subscribe_to_clock_topic(self):
         if self._clock_sub is not None and self._node is not None:
@@ -57,7 +58,8 @@ def attach_node(self, node):
         if self._node is not None:
             self.detach_node()
         self._node = node
-        self._subscribe_to_clock_topic()
+        if self.ros_time_is_active:
+            self._subscribe_to_clock_topic()
 
     def detach_node(self):
         # Remove the subscription to the clock topic.

rclpy/test/test_time_source.py

@@ -70,6 +70,7 @@ def test_time_source_not_using_sim_time(self):
         clock2._set_ros_time_is_active(True)
         time_source.attach_clock(clock2)
         self.assertFalse(clock2.ros_time_is_active)
+        assert time_source._clock_sub is None
 
     def test_time_source_using_sim_time(self):
         time_source = TimeSource(node=self.node)
@@ -84,6 +85,9 @@ def test_time_source_using_sim_time(self):
         self.assertTrue(time_source.ros_time_is_active)
         self.assertTrue(clock.ros_time_is_active)
 
+        # A subscriber should have been created
+        assert time_source._clock_sub is not None
+
         # When using sim time, ROS time should look like the messages received on /clock
         self.publish_clock_messages()
         assert clock.now() > Time(seconds=0, clock_type=ClockType.ROS_TIME)