[ros-users] Alternative package dependencies

[Dirk Thomas]

Hi,

while working on the ROS GUI SIG we think we found certain features to be missing for the ROS package dependency mechanism.
We have a package which needs at least one of two specific dependencies in order to work (i.e. PyQt binding or PySide bindings).

Specifying both dependencies would be bad as some users might not want to install both bindings (since either one would be sufficient).
Specifying no dependency would lead to a package which does not work if no bindings are available at all (making the dependency checks useless).

What we would need is to specify that the package has the dependency A "or" B.

Actually A and B might even consist of multiple packages (i.e. A would be: PyQt bindings + PyQt bindings for OpenGL + whatever).
So it might be necessary to specify dependencies like:
(A1 && A2 && A3) || (B1 && B2)

What are your thoughts on this?
Is this already possible, or would it be a feasible enhancement?

Dirk