[ros2] gazebo doesn't pick up the "out:=/scan" from turtlebot3 world file

[mkhansenbot]

Sometime this week a change has merged somewhere in ROS2 source (using ros2.repos master file), that seems to have broken Gazebo ability to rename the turtlebot3 topics like "/scan" and "/imu" (see here: https://github.com/ROBOTIS-GIT/turtlebot3_simulations/blob/ros2/turtlebot3_gazebo/models/turtlebot3_waffle/model-1_4.sdf#L160)

Now we don't see those topics but we see default ones like "/turtlebot3_laserscan/out" instead of "/scan"

Maybe this is related to the "--ros-args" changes that merged upstream? Just a guess.

To reproduce:

1. build ros2 from source using ros2.repos file.
2. build latest ros2 branch of gazebo_ros_pkgs
3. git clone https://github.com/ROBOTIS-GIT/turtlebot3_simulations.git
4. export GAZEBO_MODEL_PATH=~/turtlebot3_simulations/turtlebot3_gazebo/models
5. gazebo --verbose -s libgazebo_ros_init.so ~/turtlebot3_simulations/turtlebot3_gazebo/worlds/turtlebot3_worlds/waffle.model
6. Wait for simulation to load
7. In another window run ros2 topic echo /scan (nothing will echo)
8. ros2 topic list will not show the /scan topic, but will show /turtlebot3_laserscan/out instead

[crdelsey]

It looks like it is related to ros2/rcl#491

[chapulina]

I think from Eloquent we may need to use this in the SDF: <argument>-r ~/out:=scan</argument>. If that works, we should update all our examples and docs.

[crdelsey]

That doesn't seem to be sufficient. I'm still seeing the output on /laserscan/out instead of scan

[chapulina]

Oh sorry, maybe this?

<argument>--ros-args -r ~/out:=scan</argument>

I hope we don't need this 😓

<argument>--ros-args</argument>
<argument>-r</argument>
<argument>~/out:=scan</argument>

[mkhansenbot]

Only that last method works :(

[chapulina]

Ok, thanks for testing. I can add a new <remapping> element which prepends --ros-args and -r under the hood for convenience.

[orduno]

Since these <argument>s are all scoped within <ros>, should prepending of --ros-args happen to any <argument> and include an additional -r for any <remapping>?

          <plugin name="my_imu_plugin" filename="libgazebo_ros_imu_sensor.so">
            <ros>
              <argument>~/out:=imu</argument>
            </ros>
          </plugin>

[chapulina]

@orduno , yes, that's the current workaround.

When I have some time I want to automatically prepend --ros-args for all <argument> tags, and handle remappings separately through a <remapping> element.

Also note that upstream will soon be updated to support the old method with warnings, which should ease the transition. See ros2/rcl#495 (comment).

[shivaang12]

I also noticed the same behavior with imu when I changed <argument>~/out:=imu</argument> to <argument>--ros-args --remap ~/out:=imu</argument>.

[mikaelarguedas]

See #1011 for an attempt at implementing the <remapping> tag

Tested on turtlebot3 burger at ROBOTIS-GIT/turtlebot3_simulations@dc80aa5

[chapulina]

Fixed in #1011 for Eloquent, thanks @mikaelarguedas ! I think it's a good idea to backport the <remapping> tag to Dashing, update all examples and make that the recommended pattern. If anyone is up for submitting a PR that would be appreciated 😊

[chapulina]

I think it's a good idea to backport the tag to Dashing, update all examples and make that the recommended pattern.

At least one user is mixing dashing and eloquent and getting bad results: osrf/gazebo_tutorials#104.

Dashing still has one year of support. We could backport the remapping tag to ease users' lives.