Remove ROS-specific arguments before passing to argparse

[jacobperron]

This resolves argparse errors when trying to launch the spawn_entity script as a ROS node.

For example, a launch file like the following wouldn't work without this change:

<launch>
  <arg name="model_urdf" default="$(find-pkg-share mymodels)/urdf/ball.urdf" />
  <node
    pkg="gazebo_ros"
    exec="spawn_entity.py"
    name="spawner"
    args="-entity foo -file /path/to/my/model/foo.urdf" />
</launch>

[jacobperron]

I'm not sure what's causing the test failure, my change looks innocent enough 😇

[chapulina]

The ackermann test has been flaky.

This looks good to me 👍

[mogumbo]

Unfortunately, I still can't run spawn_entity.py as a node. If I print out args and args_without_ros, they are the same:

[spawn_entity.py-5] args = ['/home/mogumbo/workspace/install/gazebo_ros/lib/gazebo_ros/spawn_entity.py', '-entity', 'rp1a', '-file', '/tmp/rp1a_robot.urdf', '-package_to_model', '--ros-args']
[spawn_entity.py-5] args_without_ros = ['/home/mogumbo/workspace/install/gazebo_ros/lib/gazebo_ros/spawn_entity.py', '-entity', 'rp1a', '-file', '/tmp/rp1a_robot.urdf', '-package_to_model', '--ros-args']

Is something broken in rclpy.utilities.remove_ros_args?

[jacobperron]

@mogumbo 🤔 I've successfully launched spawn_entity.py as a node building the gazebo_ros_pkgs dashing branch against both ROS 2 Dashing binaries as well as the latest source. Double check that your source checkout of gazebo_ros_pkgs is up-to-date.

[mogumbo]

Thanks for testing. I have up-to-date gazebo_ros_pkgs:dashing as well. I also tried ros-dashing-rclpy from the repo and building rclpy:dashing in my workspace. Just rebuilt my whole workspace and the problem remains. I have no idea why it's behaving differently here.

[jacobperron]

Just to clarify, avoid mixing rclpy:dashing with latest versions of launch_ros or other packages.

--ros-args is new and should not appear anywhere in Dashing (ie. the remove args utility in Dashing doesn't know about --ros-args). Since we don't have XML launch files in Dashing, I would expect a launch file like this example to work (replacing the entity and path to URDF with valid values):

from launch import LaunchDescription
from launch_ros.actions import Node


def generate_launch_description():
    return LaunchDescription([
            Node(
                package='gazebo_ros',
                node_executable='spawn_entity.py',
                arguments=['-entity', 'foo', '-file', '/full/path/to/model.urdf']
            ),
        ])

I'm guessing you're experiencing some workspace shenanigans.

[mogumbo]

I don't totally understand your comment. I have ros-dashing-rclpy installed. Should I expect this to cause problems?

I have rebuilt my workspace from scratch and recompiled and I still have a --ros-args error when I launch.

[jacobperron]

I don't totally understand your comment. I have ros-dashing-rclpy installed. Should I expect this to cause problems?

It shouldn't cause problems if you're rebuilding rclpy in your workspace. To be sure, I would avoid sourcing /opt/ros/dashing/setup.* before you build your workspace.

[mogumbo]

I don't understand. How can you build a ROS2 workspace without first sourcing /opt/ros/dashing/setup.* ? The build fails immediately.

[jacobperron]

You can build everything from source. Here's instructions for building the latest from source.