Make nodes context-manager aware. (#1293)

* Make nodes context-manager aware.

This way it is much easier to create examples that properly
clean up after themselves.

* Add in testing for context managers.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>

rclpy/rclpy/node.py

@@ -15,6 +15,7 @@
 import math
 import time
 
+from types import TracebackType
 from typing import Any
 from typing import Callable
 from typing import Dict
@@ -2295,3 +2296,14 @@ def wait_for_node(
             flag = fully_qualified_node_name in fully_qualified_node_names
             time.sleep(0.1)
         return flag
+
+    def __enter__(self) -> 'Node':
+        return self
+
+    def __exit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc_val: Optional[BaseException],
+        exc_tb: Optional[TracebackType],
+    ) -> None:
+        self.destroy_node()

rclpy/test/test_node.py

@@ -2528,6 +2528,17 @@ def test_use_sim_time(self):
         finally:
             rclpy.shutdown(context=context)
 
+    def test_node_context_manager(self):
+        context = rclpy.context.Context()
+        rclpy.init(context=context)
+
+        try:
+            with rclpy.create_node('test_node_no_sim', context=context) as node:
+                self.assertTrue(node.has_parameter(USE_SIM_TIME_NAME))
+                self.assertFalse(node.get_parameter(USE_SIM_TIME_NAME).value)
+        finally:
+            rclpy.shutdown(context=context)
+
 
 def test_node_resolve_name():
     context = rclpy.Context()

rclpy/test/test_publisher.py

@@ -126,5 +126,16 @@ def test_wait_for_all_acked(self):
         sub.destroy()
 
 
+def test_publisher_context_manager():
+    rclpy.init()
+    try:
+        with rclpy.create_node('pub_node', namespace='/pub_node_ns') as node:
+            with node.create_publisher(BasicTypes, 'chatter', 1) as pub:
+                assert pub.get_subscription_count() == 0
+
+    finally:
+        rclpy.shutdown()
+
+
 if __name__ == '__main__':
     unittest.main()

rclpy/test/test_subscription.py

@@ -107,6 +107,25 @@ def test_subscription_callback_type():
     node.destroy_node()
 
 
+def test_subscription_context_manager():
+    node = Node('test_node', namespace='test_subscription/test_subscription_callback_type')
+    with node.create_subscription(
+            msg_type=Empty,
+            topic='test_subscription/test_subscription_callback_type/topic',
+            qos_profile=10,
+            callback=lambda _: None) as sub:
+        assert sub._callback_type == Subscription.CallbackType.MessageOnly
+
+    with node.create_subscription(
+            msg_type=Empty,
+            topic='test_subscription/test_subscription_callback_type/topic',
+            qos_profile=10,
+            callback=lambda _, _2: None) as sub:
+        assert sub._callback_type == Subscription.CallbackType.WithMessageInfo
+
+    node.destroy_node()
+
+
 def test_subscription_publisher_count():
     topic_name = 'test_subscription/test_subscription_publisher_count/topic'
     node = Node('test_node', namespace='test_subscription/test_subscription_publisher_count')