rospack depends on rosdep

[mikepurvis]

There's some discussion here: #5 (comment)

And I can't actually find any instances of rosdep being needed by this code: https://github.com/ros/rospack/search?q=rosdep&type=Code

Is the dependency completely vestigial at this point? If so, can it be removed?

Our deployed robots are not development platforms; rosdep should not be necessary as a runtime dependency of ROS; we'd like to eliminate having to install and initialize it.

[dirk-thomas]

Some verbs of rospack call the rosdep Python API (https://github.com/ros/rospack/search?utf8=%E2%9C%93&q=rosdep2&type=Code). So it can not be removed as a dependency.

Btw. you might not want to trust the GitHub search. It sometimes provides you only with incomplete results. E.g. in this case it didn't return you the cases where rosdep2 was found (while you searched for rosdep it assumes you want "full-word-results only").

[mikepurvis]

Oh blah, I thought I did check for rosdep2, but I was looking at other repos and must have gotten confused. Anyway, looks like the immediate affected methods are isSysPackage and cpp_exports, and then computeDepsInternal/computeDeps.

At a conceptual level, I can see rospack needing to be able to distinguish between catkin deps and system deps, but this still feels like a strange dependency to me, especially when it comes up at runtime— what is it that roslaunch and rosrun are doing which ultimately comes back as a complaint from rosdep about being uninitialized?

[dirk-thomas]

I don't know what exactly you are invoking. I don't know of anything in roslaunch which requires rosdep. E.g. I can run roslaunch roscpp_tutorials talker_listener.launch without having initialized rosdep. Please provide more information to narrow down which part of your cases uses rosdep.

[mikepurvis]

Ah.. hmm. You're right that it isn't required for a trivial invocation. We see it on our platforms and in buildroots running unit tests. I will reopen the ticket when I get a concrete MWE for where I think there's a wrongful rosdep dependency.

[mikepurvis]

Just to follow up here, it's an issue with plugin discovery. Similar report here:

moveit/moveit_ros#154

The underlying issue is with rospkg.get_depends_on and is being tracked in ros-infrastructure/rospkg#103.