Fix the launching of Servo as a node component

[AndyZe]

Description

Now that this seems to work reliably, make it the default way. It should decrease latency.

I tested with the tutorial, like normal:

https://moveit.picknik.ai/main/doc/examples/realtime_servo/realtime_servo_tutorial.html

[AndyZe]

@ibrahiminfinite

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.02 🎉

Comparison is base (9782d9a) 50.52% compared to head (7329b97) 50.53%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2194      +/-   ##
==========================================
+ Coverage   50.52%   50.53%   +0.02%     
==========================================
  Files         386      386              
  Lines       31736    31736              
==========================================
+ Hits        16032    16036       +4     
+ Misses      15704    15700       -4     

see 5 files with indirect coverage changes

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[sea-bass]

Instead of commenting things in/out, could we maybe introduce an actual launch parameter + some IfCondition / UnlessCondition logic that toggles this more cleanly?

[henningkayser]

Looks good. When are we ready to use component nodes by default? ;)

[sea-bass]

Looks good. When are we ready to use component nodes by default? ;)

If it works, I'd be totally fine with the default param being true. @AndyZe up to you if you wanna tweak that before merging.

[AndyZe]

I believe it is the default with this PR:

    launch_as_standalone_node = LaunchConfiguration(
        "launch_as_standalone_node", default="false"
    )

[sea-bass]

Woops, I got my logicals mixed up. Yes, you're right :)

[sea-bass]

Unfortunately this change actually has a bug, my apologies for not actually testing it. Turns out a component node doesn't have the ability to accept a launch condition parameter... fun

From a user on Discord,

I was following this tutorial (https://moveit.picknik.ai/main/doc/examples/realtime_servo/realtime_servo_tutorial.html#launching-a-servo-node) and after running the command:
ros2 launch moveit_servo servo_example.launch.py

I got an error:

[INFO] [launch]: Default logging verbosity is set to INFO
[ERROR] [launch]: Caught exception in launch (see debug for traceback): Caught exception when trying to load file of format [py]: ComposableNode.__init__() got an unexpected keyword argument 'condition'

Commenting out the condition argument in launch file at ~/ws_moveit/src/moveit2/moveit_ros/moveit_servo/launch/servo_example.launch.py solved my problem :

    container = launch_ros.actions.ComposableNodeContainer(
        name="moveit_servo_demo_container",
        namespace="/",
        package="rclcpp_components",
        executable="component_container_mt",
        composable_node_descriptions=[
            # Example of launching Servo as a node component
            # Launching as a node component makes ROS 2 intraprocess communication more efficient.
            launch_ros.descriptions.ComposableNode(
                package="moveit_servo",
                plugin="moveit_servo::ServoNode",
                name="servo_node",
                parameters=[
                    servo_params,
                    moveit_config.robot_description,
                    moveit_config.robot_description_semantic,
                ],
                # condition=UnlessCondition(launch_as_standalone_node), <------- Commented out(Line 98)
            ),

[sea-bass]

Update: This actually works on Rolling, but not Humble, so I think we shouldn't do much.

See ros2/launch_ros#294 for more details.

[AndyZe]

Ok. I thought I had tested it before pushing