runtime/rbs_bt_executor/launch/rbs_executor.launch.py

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch_ros.actions import Node
from launch.substitutions import Command, FindExecutable, LaunchConfiguration, PathJoinSubstitution
from launch_ros.substitutions import FindPackageShare
# from ament_index_python.packages import get_package_share_directory 
# import os

def generate_launch_description():

    declared_arguments = []
    declared_arguments.append(
        DeclareLaunchArgument(
            "bt_file",
            default_value="test_tree_env_manager.xml",
            description="BehaviorTree file for run.",
        )
    )
    bt_file = LaunchConfiguration("bt_file")

    robot_description_semantic_content = Command(
        [
            PathJoinSubstitution([FindExecutable(name="xacro")]),
            " ",
            PathJoinSubstitution(
                [FindPackageShare("ur_moveit_config"), "srdf", "ur.srdf.xacro"]
            ),
            " ",
            "name:=",
            "ur",
            " ",
            "prefix:=",
            "",
            " ",
        ]
    )
    robot_description_semantic = {"robot_description_semantic": robot_description_semantic_content}

    btfile_description = PathJoinSubstitution(
        [FindPackageShare("rbs_bt_executor"), "bt_trees", bt_file]
    )
    btfile_param = {"bt_file_path": btfile_description}

    nodes_to_start = [
        Node(
            package='behavior_tree',
            executable='bt_engine',
            # prefix=['gdbserver localhost:3000'],
            parameters=["/home/bill-finger/rbs_ws/src/robossembler-ros2/rbs_bt_executor/config/params.yaml"]
        )
    ]

    return LaunchDescription(declared_arguments + nodes_to_start)