Reject goals processed by malformed goal callbacks

Signed-off-by: Jacob Perron <jacob@openrobotics.org>

rclpy/rclpy/action/server.py

@@ -277,7 +277,11 @@ async def _execute_goal_request(self, request_header_and_message):
         if not goal_id_exists:
             # Call user goal callback
             response = await await_or_execute(self._goal_callback, goal_request)
-            accepted = GoalResponse.ACCEPT == response
+            if not isinstance(response, GoalResponse):
+                self._node.get_logger().warn(
+                    'Goal request callback did not return a GoalResponse type. Rejecting goal.')
+            else:
+                accepted = GoalResponse.ACCEPT == response
 
         if accepted:
             # Create a goal handle

rclpy/test/action/test_server.py

@@ -203,6 +203,28 @@ def handle_accepted_callback(goal_handle):
         self.assertFalse(future.result().accepted)
         action_server.destroy()
 
+    def test_goal_callback_invalid_return(self):
+
+        def goal_callback(goal):
+            return 'Invalid return type'
+
+        action_server = ActionServer(
+            self.node,
+            Fibonacci,
+            'fibonacci',
+            execute_callback=self.execute_goal_callback,
+            goal_callback=goal_callback,
+            handle_accepted_callback=lambda gh: None,
+        )
+
+        goal_msg = Fibonacci.Goal()
+        goal_msg.action_goal_id = UUID(uuid=list(uuid.uuid4().bytes))
+        future = self.mock_action_client.send_goal(goal_msg)
+        rclpy.spin_until_future_complete(self.node, future, self.executor)
+        # An invalid return type in the goal callback should translate to a rejected goal
+        self.assertFalse(future.result().accepted)
+        action_server.destroy()
+
     def test_multi_goal_accept(self):
         executor = MultiThreadedExecutor(context=self.context)
         action_server = ActionServer(