Use opaque function to allow for remapping of scan topics (#293)

* Use opaque function to allow for remapping of scan topics

turtlebot4_navigation/launch/nav2.launch.py

@@ -18,52 +18,68 @@
 from ament_index_python.packages import get_package_share_directory
 
 from launch import LaunchDescription
-from launch.actions import DeclareLaunchArgument, GroupAction, IncludeLaunchDescription
+from launch.actions import (
+    DeclareLaunchArgument,
+    GroupAction,
+    IncludeLaunchDescription,
+    OpaqueFunction
+)
 from launch.launch_description_sources import PythonLaunchDescriptionSource
 from launch.substitutions import LaunchConfiguration, PathJoinSubstitution
 
-from launch_ros.actions import PushRosNamespace
+from launch_ros.actions import PushRosNamespace, SetRemap
 
 
 ARGUMENTS = [
     DeclareLaunchArgument('use_sim_time', default_value='false',
                           choices=['true', 'false'],
                           description='Use sim time'),
+    DeclareLaunchArgument('params_file',
+                          default_value=PathJoinSubstitution([
+                              get_package_share_directory('turtlebot4_navigation'),
+                              'config',
+                              'nav2.yaml'
+                              ]),
+                          description='Nav2 parameters'),
+    DeclareLaunchArgument('namespace', default_value='',
+                          description='Robot namespace')
 ]
 
 
-def generate_launch_description():
-    pkg_turtlebot4_navigation = get_package_share_directory('turtlebot4_navigation')
+def launch_setup(context, *args, **kwargs):
     pkg_nav2_bringup = get_package_share_directory('nav2_bringup')
 
-    nav2_params_arg = DeclareLaunchArgument(
-        'params_file',
-        default_value=PathJoinSubstitution(
-            [pkg_turtlebot4_navigation, 'config', 'nav2.yaml']),
-        description='Nav2 parameters')
-
-    namespace_arg = DeclareLaunchArgument(
-                        'namespace',
-                        default_value='',
-                        description='Robot namespace')
-
+    nav2_params = LaunchConfiguration('params_file')
     namespace = LaunchConfiguration('namespace')
     use_sim_time = LaunchConfiguration('use_sim_time')
 
+    namespace_str = namespace.perform(context)
+    if (namespace_str and not namespace_str.startswith('/')):
+        namespace_str = '/' + namespace_str
+
+    launch_nav2 = PathJoinSubstitution(
+        [pkg_nav2_bringup, 'launch', 'navigation_launch.py'])
+
     nav2 = GroupAction([
         PushRosNamespace(namespace),
+        SetRemap(namespace_str + '/global_costmap/scan', namespace_str + '/scan'),
+        SetRemap(namespace_str + '/local_costmap/scan', namespace_str + '/scan'),
 
         IncludeLaunchDescription(
-            PythonLaunchDescriptionSource(
-                PathJoinSubstitution(
-                    [pkg_nav2_bringup, 'launch', 'navigation_launch.py'])),
-            launch_arguments={'use_sim_time': use_sim_time,
-                              'use_composition': 'False',
-                              'params_file': LaunchConfiguration('params_file')}.items()),
+            PythonLaunchDescriptionSource(launch_nav2),
+            launch_arguments=[
+                  ('use_sim_time', use_sim_time),
+                  ('params_file', nav2_params.perform(context)),
+                  ('use_composition', 'False'),
+                  ('namespace', namespace_str)
+                ]
+        ),
     ])
 
+    return [nav2]
+
+
+def generate_launch_description():
     ld = LaunchDescription(ARGUMENTS)
-    ld.add_action(nav2_params_arg)
-    ld.add_action(namespace_arg)
-    ld.add_action(nav2)
+    ld.add_action(OpaqueFunction(function=launch_setup))
     return ld