Add tests for issue ros2#180 functionality

  - Check that timers will shut down a launched system
  - Check that shutdown will cancel a timer without cancel_on_shutdown=False
  - Check that shutdown will not cancel a timre with cancel_on_shutdown=True

launch/test/launch/test_timer_action.py

@@ -13,8 +13,12 @@
 # limitations under the License.
 
 
+"""Tests for the TimerAction Action."""
+import sys
+
 import launch
 import launch.actions
+import launch.event_handlers
 
 
 def test_multiple_launch_with_timers():
@@ -24,6 +28,11 @@ def test_multiple_launch_with_timers():
 
     def generate_launch_description():
         return launch.LaunchDescription([
+
+            launch.actions.ExecuteProcess(
+                cmd=[sys.executable, '-c', 'while True: pass'],
+            ),
+
             launch.actions.TimerAction(
                 period='1',
                 actions=[
@@ -34,9 +43,113 @@ def generate_launch_description():
 
     ls = launch.LaunchService()
     ls.include_launch_description(generate_launch_description())
-    assert 0 == ls.run(shutdown_when_idle=False)  # Always works
+    assert 0 == ls.run()  # Always works
 
     ls = launch.LaunchService()
     ls.include_launch_description(generate_launch_description())
     # Next line hangs forever before https://github.com/ros2/launch/issues/183 was fixed.
-    assert 0 == ls.run(shutdown_when_idle=False)
+    assert 0 == ls.run()
+
+
+def _shutdown_listener_factory(reasons_arr):
+    return launch.actions.RegisterEventHandler(
+        launch.event_handlers.OnShutdown(
+            on_shutdown=lambda event, context: reasons_arr.append(event)
+        )
+    )
+
+
+def test_timer_action_sanity_check():
+    """Test that timer actions work (sanity check)."""
+    # This test is structured like test_shutdown_preempts_timers and
+    # test_timer_can_block_preemption as a sanity check that the shutdown listener
+    # and other launch related infrastructure works as expected
+    shutdown_reasons = []
+
+    ld = launch.LaunchDescription([
+        launch.actions.ExecuteProcess(
+            cmd=[sys.executable, '-c', 'while True: pass'],
+        ),
+
+        launch.actions.TimerAction(
+            period='1',
+            actions=[
+                launch.actions.Shutdown(reason='One second timeout')
+            ]
+        ),
+
+        _shutdown_listener_factory(shutdown_reasons),
+    ])
+
+    ls = launch.LaunchService()
+    ls.include_launch_description(ld)
+    assert 0 == ls.run()
+    assert shutdown_reasons[0].reason == 'One second timeout'
+
+
+def test_shutdown_preempts_timers():
+    shutdown_reasons = []
+
+    ld = launch.LaunchDescription([
+
+        launch.actions.ExecuteProcess(
+            cmd=[sys.executable, '-c', 'while True: pass'],
+        ),
+
+        launch.actions.TimerAction(
+            period='1',
+            actions=[
+                launch.actions.Shutdown(reason='fast shutdown')
+            ]
+        ),
+
+        launch.actions.TimerAction(
+            period='2',
+            actions=[
+                launch.actions.Shutdown(reason='slow shutdown')
+            ]
+        ),
+
+        _shutdown_listener_factory(shutdown_reasons),
+    ])
+
+    ls = launch.LaunchService()
+    ls.include_launch_description(ld)
+    assert 0 == ls.run()
+    assert len(shutdown_reasons) == 1
+    assert shutdown_reasons[0].reason == 'fast shutdown'
+
+
+def test_timer_can_block_preemption():
+    shutdown_reasons = []
+
+    ld = launch.LaunchDescription([
+
+        launch.actions.ExecuteProcess(
+            cmd=[sys.executable, '-c', 'while True: pass'],
+        ),
+
+        launch.actions.TimerAction(
+            period='1',
+            actions=[
+                launch.actions.Shutdown(reason='fast shutdown')
+            ]
+        ),
+
+        launch.actions.TimerAction(
+            period="2",
+            actions=[
+                launch.actions.Shutdown(reason='slow shutdown')
+            ],
+            cancel_on_shutdown=False  # Preempted in test_shutdown_preempts_timers, but not here
+        ),
+
+        _shutdown_listener_factory(shutdown_reasons),
+    ])
+
+    ls = launch.LaunchService()
+    ls.include_launch_description(ld)
+    assert 0 == ls.run()
+    assert len(shutdown_reasons) == 2  # Should see 'shutdown' event twice because
+    assert shutdown_reasons[0].reason == 'fast shutdown'
+    assert shutdown_reasons[1].reason == 'slow shutdown'