Run condition for composable nodes

[adityapande-1995]

Signed-off-by: Aditya aditya050995@gmail.com

Summary

This PR adds the condition parameter to composable nodes action. Resolves #294. This action is currently supported by ComposableNodeContainer but not ComposableNode itself.

Example usage

One can use the following example file :

import launch
import launch.actions
from launch.conditions import IfCondition, UnlessCondition
from launch.substitutions import LaunchConfiguration
import launch_ros.actions
from launch_ros.actions import ComposableNodeContainer
from launch_ros.descriptions import ComposableNode

def generate_launch_description():
    return launch.LaunchDescription([
        launch.actions.DeclareLaunchArgument(name='flag', default_value='False'),
        ComposableNodeContainer(
            name='my_container',
            namespace='',
            package='rclcpp_components',
            executable='component_container',

            composable_node_descriptions=[
                ComposableNode(
                    package='composition',
                    plugin='composition::Talker',
                    condition=IfCondition(LaunchConfiguration('flag')),
                    name='talker_1'),

                ComposableNode(
                    package='composition',
                    plugin='composition::Talker',
                    condition=UnlessCondition(LaunchConfiguration('flag')),
                    name='talker_2'),

                ComposableNode(
                    package='composition',
                    plugin='composition::Talker',
                    name='talker_3'),
            ],
            output='screen',
        ),
    ]) 

or alternatively as an xml,

<launch>
        <arg name="flag" default="false"/>
        <node_container pkg="rclcpp_components" exec="component_container" name="my_container" namespace="">
                <composable_node pkg="composition" plugin="composition::Talker" name="talker_1" if="$(var flag)" />
                <composable_node pkg="composition" plugin="composition::Talker" name="talker_2" unless="$(var flag)" />
                <composable_node pkg="composition" plugin="composition::Talker" name="talker_3" />
        </node_container>
</launch>

Running this as ros2 launch test.py flag:=True will make it launch talker_1 and talker_3, and False will make it launch talker_2 and talker_3.

[ivanpauno]

LGTM!

[ivanpauno]

@adityapande-1995 could you fix CI failures?

[adityapande-1995]

CI :
build : --packages-above-and-dependencies launch_ros
test : --packages-above launch_ros

• Linux
• Linux-aarch64
• Windows []

[adityapande-1995]

CI round 2 with flake8 fixes :

• Linux
• Linux-aarch64
• Windows []

[adityapande-1995]

Got green CI, merging !

[sea-bass]

Any chance this can be backported to Humble? We just had a MoveIt user find an issue with something related to this change not being in Humble.

[mjcarroll]

Any chance this can be backported to Humble? We just had a MoveIt user find an issue with something related to this change not being in Humble.

I don't see any reason why not after looking at it. Care to open a PR?

[clalancette]

@Mergifyio backport humble

[mergify]

backport humble

✅ Backports have been created

• #363 Run condition for composable nodes (backport #311) has been created for branch humble