Use optional parameters in actions

[caguero]

🦟 Bug fix

Fixes #554

Summary

This patch lets you use <ros_gz_bridge> and <gz_server> XML elements without having to declare all its arguments.

Testing the bridge

You can modify ros_gz_bridge/launch/ros_gz_bridge.launch with the following content (change your config_file path accordingly):

<launch>
  <ros_gz_bridge
    name="bridge"
    config_file="/home/caguero/ros_gz_ws/src/ros_gz/ros_gz_bridge/test/config/full.yaml" />
</launch>

Launch a ROS container:

ros2 run rclcpp_components component_container --ros-args -r __node:=ros_gz_container

Launch the bridge:

ros2 launch ros_gz_bridge ros_gz_bridge.launch

Verify that the component is loaded:

caguero@cold:~/ros_gz_ws$ ros2 component list
/ros_gz_container
  1  /bridge

Verify that the /ros_chatter topic is listed:

caguero@cold:~/ros_gz_ws$ ros2 topic list
/parameter_events
/ros_chatter
/rosout

Testing ros_gz_sim

Modify ros_gz_sim/launch/ros_gz_sim.launch with (change your config_file path accordingly):

<launch>
  <gz_server
    world_sdf_file="empty.sdf" />
  <ros_gz_bridge
    name="bridge"
    config_file="/home/caguero/ros_gz_ws/src/ros_gz/ros_gz_bridge/test/config/full.yaml" />
</launch>

Launch gzserver and the bridge:

ros2 launch ros_gz_sim ros_gz_sim.launch

Verify that the two components are loaded:

caguero@cold:~/ros_gz_ws$ ros2 component list
/ros_gz_container
  1  /gz_server
  2  /bridge

Verify that you see the logging messages from gzserver on the terminal and that the /ros_chatter topic is listed:

caguero@cold:~/ros_gz_ws$ ros2 topic list
/parameter_events
/ros_chatter
/rosout

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[azeey]

Is it still possible to pass this launch file some of the arguments? i.e, can we call ros2 launch ros_gz_sim.launch world_sdf_file=path/to/file.sdf? I'm not, I don't see why we need this file at all.

[caguero]

This change was unintentional. Fixed in #603.