"ROS" packages already in nixpkgs

[nim65s]

Hi,

Could we override some packages from the overlay to directly use those provided by nixpkgs, instead of trying to re-declare and re-build things from ROS ?

Context: I'm the maintainer (upstream + nixpkgs + ROS) of a few things (eg. eigenpy / hpp-fcl / pinocchio): pinocchio is in better shape in nixpkgs than in ROS. For example in nixpkgs we can enable the casadi optional dependency, while in ROS that's harder since casadi is not packaged in ubuntu.

Also, since pinocchio requires lot of RAM and time to build, I think it would be very beneficial for your build & cache infra :)

NB: I'm speaking of non-ROS-only packages, which are packaged in rosdistro. Maybe it make little or no difference for pure ROS packages, but version constraints might be harder.

[nim65s]

Hum, wait, that's already the case, isn't it ?
You're wonderful, thank you.

[nim65s]

Actually, that's half the case, this is why I was mislead in the first place:

$ nix repl
Lix 2.91.1
Type :? for help.
nix-repl> :lf github:lopsided98/nix-ros-overlay
Added 17 variables.

nix-repl> outputs.legacyPackages.x86_64-linux.humble.pinocchio                 
«derivation /nix/store/ka5slb3x93ky1k8s1i7710qdpbwlq1fi-ros-humble-pinocchio-2.6.21-r1.drv»

nix-repl> outputs.legacyPackages.x86_64-linux.humble.python3Packages.pinocchio
«derivation /nix/store/gac53bw2ryvinpyf40rfwc3b5mpkskgw-pinocchio-3.2.0.drv»

Pinocchio is both available as a C++ library and a python module, and, here, the 2.6.21r1 C++ library is from rosdistro, and the 3.2.0 python module from nixpkgs

[hacker1024]

This occurs because ROS packages are in one scope, while Python packages are in another. Using a ROS callPackage will shadow Nixpkgs packages from the scope above, but not packages in the Python scope.

i.e.

rosPackages.rolling.callPackage ({
  buildRosPackage
, pinocchio # Shadowed by the ROS definition
, python3Packages # Not defined by this overlay, so straight from Nixpkgs
}: buildRosPackage { /* ... */ }) { };

It would probably be a good idea to check for existing packages either in Superflore or in a step after running it.

---

rtabmap is another shadowed package that would benefit from this. I have a personal overlay that uses the Nixpkgs definition with the nix-ros-overlay version and source:

rtabmap = self.rtabmap.overrideAttrs {
  inherit (rosSuper.rtabmap)
    pname
    version
    src;
};