Switch between catkin and ament based on ROS_VERSION

[mpowelson]

This makes it easier to use with ROS 2. Otherwise you have to add a rosdep skip-key on catkin. REP-136 looks to be well before ROS 2 and ament were in the picture.

[awinkler]

That tag was needed/recommended for releasing binaries and for the ros build farm. Could you kindly provide a bit more info why you think it is now obsolete. https://www.ros.org/reps/rep-0136.html

[mpowelson]

Perhaps it isn't. I didn't realize that was required for the build farm. However, when running rosdep on this on a ROS 2 system it complains that it can't find catkin (since it isn't released). HERE is the specific motivator. I assume for releasing this on ROS 2 it would have to be changed to <exec_depend>ament</exec_depend>.

Adding it to the skip-keys isn't that big of a deal, and many people running ROS 2 may already have catkin added for other things. I'm not sure what the recommendation is. Perhaps @gavanderhoorn or @Levi-Armstrong would know.

[wxmerkt]

@mpowelson Is it possible to upgrade to package format 3 and use a condition?

As in:

<exec_depend condition="$ROS_VERSION == 1">catkin</exec_depend>
<exec_depend condition="$ROS_VERSION == 2">ament</exec_depend>

[mpowelson]

That sounds reasonable to me.

[awinkler]

@mpowelson Is it possible to upgrade to package format 3 and use a condition?

As in:

<exec_depend condition="$ROS_VERSION == 1">catkin</exec_depend>
<exec_depend condition="$ROS_VERSION == 2">ament</exec_depend>

Yes, let's do this. @mpowelson could you kindly try this on your system and update the PR with the necessarily changes. Thanks!

[mpowelson]

This works fine. Here is our downstream project ROS 2 CI build using this branch.