On Thu, Sep 1, 2011 at 8:36 PM, Kevin Walchko <kevin.walchko@gmail.com> wrote:
> Hi,
>
> I have been busy playing with homebrew and ROS and changing rosdep.yaml files. I did not realize there were so many spread all over the place and some of them repeat the same thing. Has there been any though to having one main rosdep.yaml file for ROS so you only have to change things in one place? Maybe in the common_rosdeps stack?

The short answer: we tried that, it didn't work out so well.

Longer answer:

 1. If you see rosdep.yamls repeating the same thing, that's probably
worth a ticket.  In general, common dependencies should migrate
upwards.  There is some heavy-ness in the main ros/rosdep.yaml file,
but we are slowly trying to migrate that out.

 2. Having a monolithic rosdep.yaml sets up some problematic conditions.

First, it makes every stack depend on a particular, frequently
changing file.  When we had a monolithic file, we were having to put
out 4GB+ debian updates because we had to rebuild every stack just
because we got patches for Fedora or the like.

Second, it locks in every ROS stack to the same integration decision.
Given the variety of platforms that ROS runs on, we wish to minimize
this as much as possible and only lock in the choices that are
widespread (e.g. boost, python).

Third, you start losing track of which of the rosdep entries are
actually useful.  You have to perform exhaustive audits to figure out
if a rosdep is actually used (I've slowly been trying to purge the
entries in ros/rosdep.yaml and have run into this problem).

There are potentially other ways to address these issues, but a single
monolithic file has already been tried and moved away from.

 - Ken

> Curious.
>
> Kevin
>
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