Workaround for unsupported params file syntax in composable node python launch [Foxy]

ouster-ros/config/os_sensor_cloud_image_params.yaml

@@ -29,4 +29,5 @@ ouster/os_cloud:
                   # value the range [0, sensor_beams_count)
     point_type: original # choose from: {original, native, xyz, xyzi, xyzir}
 ouster/os_image:
+  ros__parameters:
     use_system_default_qos: False # needs to match the value defined for os_sensor node

ouster-ros/launch/sensor.composite.launch.py

@@ -4,63 +4,55 @@
 """Launch ouster nodes using a composite container"""
 
 from pathlib import Path
-import launch
+from launch import LaunchDescription, LaunchContext, LaunchDescriptionEntity
 from ament_index_python.packages import get_package_share_directory
 from launch_ros.actions import ComposableNodeContainer
 from launch_ros.descriptions import ComposableNode
 from launch.actions import (DeclareLaunchArgument, IncludeLaunchDescription,
-                            ExecuteProcess, TimerAction)
+                            ExecuteProcess, TimerAction, OpaqueFunction)
 from launch.conditions import IfCondition
 from launch.launch_description_sources import PythonLaunchDescriptionSource
 from launch.substitutions import LaunchConfiguration, FindExecutable
 
+import yaml
+from typing import Optional, List
 
-def generate_launch_description():
+def composable_node_setup(context: LaunchContext) -> Optional[List[LaunchDescriptionEntity]]:
     """
-    Generate launch description for running ouster_ros components in a single
-    process/container.
+    Generating launch description for composable nodes with correctly parsed node parameters,
+    this is a workaround for issue https://github.com/ros2/launch_ros/issues/156 in foxy.
     """
-    ouster_ros_pkg_dir = get_package_share_directory('ouster_ros')
-    default_params_file = \
-        Path(ouster_ros_pkg_dir) / 'config' / 'os_sensor_cloud_image_params.yaml'
     params_file = LaunchConfiguration('params_file')
-    params_file_arg = DeclareLaunchArgument('params_file',
-                                            default_value=str(
-                                                default_params_file),
-                                            description='name or path to the parameters file to use.')
-
     ouster_ns = LaunchConfiguration('ouster_ns')
-    ouster_ns_arg = DeclareLaunchArgument(
-        'ouster_ns', default_value='ouster')
 
-    rviz_enable = LaunchConfiguration('viz')
-    rviz_enable_arg = DeclareLaunchArgument('viz', default_value='True')
+    with open(params_file.perform(context), 'r') as f:
+        ros_params = yaml.safe_load(f)
 
     os_sensor = ComposableNode(
         package='ouster_ros',
         plugin='ouster_ros::OusterSensor',
         name='os_sensor',
         namespace=ouster_ns,
-        parameters=[params_file]
+        parameters=[ros_params[ouster_ns.perform(context) + '/os_sensor']['ros__parameters']]
     )
 
     os_cloud = ComposableNode(
         package='ouster_ros',
         plugin='ouster_ros::OusterCloud',
         name='os_cloud',
         namespace=ouster_ns,
-        parameters=[params_file]
+        parameters=[ros_params[ouster_ns.perform(context) + '/os_cloud']['ros__parameters']]
     )
 
     os_image = ComposableNode(
         package='ouster_ros',
         plugin='ouster_ros::OusterImage',
         name='os_image',
         namespace=ouster_ns,
-        parameters=[params_file]
+        parameters=[ros_params[ouster_ns.perform(context) + '/os_image']['ros__parameters']]
     )
 
-    os_container = ComposableNodeContainer(
+    return [ComposableNodeContainer(
         name='os_container',
         namespace=ouster_ns,
         package='rclcpp_components',
@@ -71,7 +63,28 @@ def generate_launch_description():
             os_image
         ],
         output='screen',
-    )
+    )]
+
+
+def generate_launch_description():
+    """
+    Generate launch description for running ouster_ros components in a single
+    process/container.
+    """
+    ouster_ros_pkg_dir = get_package_share_directory('ouster_ros')
+    default_params_file = \
+        Path(ouster_ros_pkg_dir) / 'config' / 'os_sensor_cloud_image_params.yaml'
+    params_file_arg = DeclareLaunchArgument('params_file',
+                                            default_value=str(
+                                                default_params_file),
+                                            description='name or path to the parameters file to use.')
+
+    ouster_ns = LaunchConfiguration('ouster_ns')
+    ouster_ns_arg = DeclareLaunchArgument(
+        'ouster_ns', default_value='ouster')
+
+    rviz_enable = LaunchConfiguration('viz')
+    rviz_enable_arg = DeclareLaunchArgument('viz', default_value='True')
 
     rviz_launch_file_path = \
         Path(ouster_ros_pkg_dir) / 'launch' / 'rviz.launch.py'
@@ -93,12 +106,12 @@ def invoke_lifecycle_cmd(node_name, verb):
     sensor_configure_cmd = invoke_lifecycle_cmd('os_sensor', 'configure')
     sensor_activate_cmd = invoke_lifecycle_cmd('os_sensor', 'activate')
 
-    return launch.LaunchDescription([
+    return LaunchDescription([
         params_file_arg,
         ouster_ns_arg,
         rviz_enable_arg,
         rviz_launch,
-        os_container,
+        OpaqueFunction(function=composable_node_setup),
         sensor_configure_cmd,
         TimerAction(period=1.0, actions=[sensor_activate_cmd])
     ])