Cleaned up launch file example_1/rrbot.launch.py

example_1/bringup/launch/rrbot.launch.py

@@ -17,109 +17,99 @@
 from launch.actions import DeclareLaunchArgument, RegisterEventHandler
 from launch.conditions import IfCondition
 from launch.event_handlers import OnProcessExit
-from launch.substitutions import Command, FindExecutable, LaunchConfiguration, PathJoinSubstitution
+from launch.substitutions import Command, LaunchConfiguration, PathSubstitution
 
 from launch_ros.actions import Node
 from launch_ros.substitutions import FindPackageShare
 
 
 def generate_launch_description():
-    # Declare arguments
-    declared_arguments = []
-    declared_arguments.append(
-        DeclareLaunchArgument(
-            "gui",
-            default_value="true",
-            description="Start RViz2 automatically with this launch file.",
-        )
-    )
-
-    # Initialize Arguments
-    gui = LaunchConfiguration("gui")
-
-    # Get URDF via xacro
-    robot_description_content = Command(
-        [
-            PathJoinSubstitution([FindExecutable(name="xacro")]),
-            " ",
-            PathJoinSubstitution(
-                [
-                    FindPackageShare("ros2_control_demo_example_1"),
-                    "urdf",
-                    "rrbot.urdf.xacro",
-                ]
-            ),
-        ]
-    )
-    robot_description = {"robot_description": robot_description_content}
-
-    robot_controllers = PathJoinSubstitution(
-        [
-            FindPackageShare("ros2_control_demo_example_1"),
-            "config",
-            "rrbot_controllers.yaml",
-        ]
-    )
-    rviz_config_file = PathJoinSubstitution(
-        [FindPackageShare("ros2_control_demo_description"), "rrbot/rviz", "rrbot.rviz"]
-    )
-
-    control_node = Node(
-        package="controller_manager",
-        executable="ros2_control_node",
-        parameters=[robot_controllers],
-        output="both",
-    )
-    robot_state_pub_node = Node(
-        package="robot_state_publisher",
-        executable="robot_state_publisher",
-        output="both",
-        parameters=[robot_description],
-    )
-    rviz_node = Node(
-        package="rviz2",
-        executable="rviz2",
-        name="rviz2",
-        output="log",
-        arguments=["-d", rviz_config_file],
-        condition=IfCondition(gui),
-    )
-
-    joint_state_broadcaster_spawner = Node(
-        package="controller_manager",
-        executable="spawner",
-        arguments=["joint_state_broadcaster"],
-    )
-
+    # Define Node action objects needed to be referenced by RegisterEventHandler
     robot_controller_spawner = Node(
         package="controller_manager",
         executable="spawner",
-        arguments=["forward_position_controller", "--param-file", robot_controllers],
-    )
-
-    # Delay rviz start after `joint_state_broadcaster`
-    delay_rviz_after_joint_state_broadcaster_spawner = RegisterEventHandler(
-        event_handler=OnProcessExit(
-            target_action=joint_state_broadcaster_spawner,
-            on_exit=[rviz_node],
-        )
+        arguments=[
+            "forward_position_controller",
+            "--param-file",
+            PathSubstitution(FindPackageShare("ros2_control_demo_example_1"))
+            / "config"
+            / "rrbot_controllers.yaml",
+        ],
     )
 
-    # Delay start of joint_state_broadcaster after `robot_controller`
-    # TODO(anyone): This is a workaround for flaky tests. Remove when fixed.
-    delay_joint_state_broadcaster_after_robot_controller_spawner = RegisterEventHandler(
-        event_handler=OnProcessExit(
-            target_action=robot_controller_spawner,
-            on_exit=[joint_state_broadcaster_spawner],
-        )
+    return LaunchDescription(
+        [
+            DeclareLaunchArgument(
+                "gui",
+                default_value="true",
+                description="Start RViz2 automatically with this launch file.",
+            ),
+            # Control node
+            Node(
+                package="controller_manager",
+                executable="ros2_control_node",
+                parameters=[
+                    PathSubstitution(FindPackageShare("ros2_control_demo_example_1"))
+                    / "config"
+                    / "rrbot_controllers.yaml"
+                ],
+                output="both",
+            ),
+            # robot_state_publisher with robot_description from xacro
+            Node(
+                package="robot_state_publisher",
+                executable="robot_state_publisher",
+                output="both",
+                parameters=[
+                    {
+                        "robot_description": Command(
+                            [
+                                "xacro",
+                                " ",
+                                PathSubstitution(FindPackageShare("ros2_control_demo_example_1"))
+                                / "urdf"
+                                / "rrbot.urdf.xacro",
+                            ]
+                        )
+                    }
+                ],
+            ),
+            # Include the robot_controller_spawner action (starts at launch)
+            robot_controller_spawner,
+            # When robot_controller_spawner exits, start the joint_state_broadcaster
+            RegisterEventHandler(
+                event_handler=OnProcessExit(
+                    target_action=robot_controller_spawner,
+                    on_exit=[
+                        joint_state_broadcaster_spawner := Node(
+                            package="controller_manager",
+                            executable="spawner",
+                            arguments=["joint_state_broadcaster"],
+                        )
+                    ],
+                )
+            ),
+            # When joint_state_broadcaster_spawner exits, start RViz
+            RegisterEventHandler(
+                event_handler=OnProcessExit(
+                    target_action=joint_state_broadcaster_spawner,
+                    on_exit=[
+                        Node(
+                            package="rviz2",
+                            executable="rviz2",
+                            name="rviz2",
+                            output="log",
+                            arguments=[
+                                "-d",
+                                PathSubstitution(FindPackageShare("ros2_control_demo_description"))
+                                / "rrbot"
+                                / "rviz"
+                                / "rrbot.rviz",
+                            ],
+                            condition=IfCondition(LaunchConfiguration("gui")),
+                        )
+                    ],
+                )
+            ),
+        ]
     )
-
-    nodes = [
-        control_node,
-        robot_state_pub_node,
-        robot_controller_spawner,
-        delay_rviz_after_joint_state_broadcaster_spawner,
-        delay_joint_state_broadcaster_after_robot_controller_spawner,
-    ]
-
-    return LaunchDescription(declared_arguments + nodes)