openarm_ros2/openarm_description/launch/description.launch.py

from pathlib import Path

import launch
from launch.substitutions import Command
from launch.substitutions import LaunchConfiguration
from launch.actions import DeclareLaunchArgument

import launch_ros
from launch_ros.parameter_descriptions import ParameterValue


def generate_launch_description():
    pkg_share = Path(
        launch_ros.substitutions.FindPackageShare(package="openarm_description").find(
            "openarm_description"
        )
    )
    default_model_path = pkg_share / "urdf/openarm.urdf.xacro"

    use_sim_time = LaunchConfiguration("use_sim_time")
    use_sim_time_launch_arg = DeclareLaunchArgument("use_sim_time", default_value="true")

    robot_state_publisher_node = launch_ros.actions.Node(
        package="robot_state_publisher",
        executable="robot_state_publisher",
        parameters=[
            {
                # ParameterValue is required to avoid being interpreted as YAML.
                "robot_description": ParameterValue(
                    Command(["xacro ", LaunchConfiguration("model")]), value_type=str
                ),
                "use_sim_time": use_sim_time,
            },
        ],
    )

    return launch.LaunchDescription(
        [
            launch.actions.DeclareLaunchArgument(
                name="model",
                default_value=str(default_model_path),
                description="Absolute path to the robot's URDF file",
            ),
            use_sim_time_launch_arg,
            robot_state_publisher_node,
        ]
    )