How to cause the entire ros2 launch process to die when a specific node exits with an error code.

debug_node_exit.launch.py

# This is useful for testing buggy ros launch setups,
# because you can run it like `while ros2 launch pkg debug.launch.py; do sleep 0.5; done;`
# and it will keep restarting util the test node returns an error.
# this was really difficult to figure out how to do.... :(
import os
import sys
from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument, RegisterEventHandler, EmitEvent
from launch.event_handlers import OnProcessExit
from launch.events import Shutdown
from launch.events.process import ProcessExited
from launch.substitutions import LaunchConfiguration, Command
from launch_ros.actions import Node
from launch_ros.parameter_descriptions import ParameterValue
from ament_index_python.packages import get_package_share_directory


def generate_launch_description():
    # Declare launch arguments
    fake_hardware_arg = DeclareLaunchArgument("fake_hardware", default_value="false")
    start_hands_arg = DeclareLaunchArgument("start_hands", default_value="false")
    ip_left_arm_arg = DeclareLaunchArgument(
        "ip_left_arm", default_value="192.168.100.85"
    )
    ip_right_arm_arg = DeclareLaunchArgument(
        "ip_right_arm", default_value="192.168.100.63"
    )
    p2_config_file_arg = DeclareLaunchArgument(
        "p2_config_file",
        default_value=os.path.join(
            get_package_share_directory("p2_4_hardware"), "config/p2_4_hardware.yaml"
        ),
    )

    # Robot description using xacro
    robot_description = Command(
        [
            "xacro ",
            os.path.join(
                get_package_share_directory("p2_4_description"), "robot/p2_4.urdf.xacro"
            ),
            " p2_config_file:=",
            LaunchConfiguration("p2_config_file"),
            " fake_hardware:=",
            LaunchConfiguration("fake_hardware"),
            " ip_left_arm:=",
            LaunchConfiguration("ip_left_arm"),
            " ip_right_arm:=",
            LaunchConfiguration("ip_right_arm"),
            " start_hands:=",
            LaunchConfiguration("start_hands"),
        ]
    )

    # Nodes
    controller_manager_node = Node(
        package="controller_manager",
        executable="ros2_control_node",
        arguments=["--ros-args", "--log-level", "controller_manager:=INFO"],
        parameters=[LaunchConfiguration("p2_config_file")],
        remappings=[("~/robot_description", "/robot_description")],
    )

    spawner_node = Node(
        package="controller_manager",
        executable="spawner",
        name="broadcaster_spawner",
        arguments=[
            "--controller-manager-timeout",
            "50",
            "joint_state_broadcaster",
            "joint_trajectory_controller_head",
            "joint_trajectory_controller_torso",
            "joint_trajectory_controller_left",
            "joint_trajectory_controller_right",
        ],
    )

    robot_state_publisher_node = Node(
        package="robot_state_publisher",
        executable="robot_state_publisher",
        parameters=[
            {"robot_description": ParameterValue(robot_description, value_type=str)}
        ],
        remappings=[("joint_states", "/joint_states")],
    )

    test_jtc_topics_node = Node(
        package="p2_4_hardware",
        executable="test_jtc_topics.py",
        name="test_jtc_topics",
        output="screen",
    )

    def on_node_exit(event: ProcessExited, *args):
        return_code = event.returncode
        if return_code == 1:
            # This allows us to tell easily from the result of the full `ros2 launch` command
            # whether the test failed or not.
            sys.exit(2)
        return EmitEvent(event=Shutdown())

    # Event handler: when test_jtc_topics_node exits, shutdown all
    shutdown_on_test_exit = RegisterEventHandler(
        OnProcessExit(target_action=test_jtc_topics_node, on_exit=on_node_exit),
    )

    # import pdb; pdb.set_trace()
    return LaunchDescription(
        [
            fake_hardware_arg,
            ip_left_arm_arg,
            ip_right_arm_arg,
            p2_config_file_arg,
            start_hands_arg,
            controller_manager_node,
            robot_state_publisher_node,
            spawner_node,
            test_jtc_topics_node,
            shutdown_on_test_exit,
        ]
    )