!!! This is a Work-in-Progress !!!

Quick Start

To enter a nix-shell with the ROS Kinetic Comm variant available, run,

$ nix-shell ros.nix

(Note that building everything takes some time!). This is actually a slight extension of the stock comm variant so that the turtlesim tutorial can run.

Regenerating a ROS Distribution

If you want to regenerate the kinetic_perception.nix file that defines all the ROS packages that make up the distribution, you will use the ros2nix program:

$ stack exec ros2nix -- $(nix-build --no-out-link ./ros-distro.nix -A kinetic.perception-src)/kinetic_perception.rosinstall -o kinetic_perception.nix

Other ROS Versions and Variants

If you want to use a different ROS distribution or variant, change the -A kinetic.perception-src part of the ros2nix incantation. If you want to use a minimal set of core packages, consider using kinetic.ros_comm-src for the comm ROS configuration.

What it's doing

• The ros-distro.nix file uses ROS tooling to obtain a .rosinstall file for the desired metapackage/variant (in the above examples, we referred to the perception and comm variants of the ROS kinetic distribution).

• The ros2nix program (called with stack exec above) generates derivations for all the packages that make up the ROS distribution. In the example, we output those definitions to the file kinetic_perception.nix.

• The ros.nix file identifies that we want to load kinetic_comm.nix and extend it with, for the sake of a satisfying example, turtlesim.nix. The full environment is constructed by mixing fixed ROS environment components specified in ros-build-env.nix with the specific package set identified by, for example, kinetic_comm.nix.

• Entering a nix-shell ros.nix sets up the ROS_PACKAGE_PATH, ROS_MASTER_URI, and the PYTHONPATH such that each package can be found.

To see if things are working, try starting a master node!

Example usage

In one shell,

$ nix-shell ros.nix
$ roscore

In another,

$ nix-shell ros.nix
$ rosrun turtlesim turtlesim_node

and in yet another,

$ nix-shell ros.nix
$ rosrun turtlesim turtle_teleop_key

Ugly Gotchas to be Fixed

Hash Caching

The ros2nix program uses a cache mapping package names to Nix hashes of their source. The way that I generate the cache is by loading src/Main.hs in a GHCi REPL, and calling generateCache "/nix/store/..../kinetic_perception.rosinstall" "perception_hash_cache.txt". The ros2nix program looks for that file, and, if it exists, uses it as a cache. If the file does not exist, it will download each ROS package. The use of this cache file was primarily intended for the development of ros2nix when it was being repeatedly run against the same .rosinstall files. It might not be necessary as the program stabilizes and is used less frequently.

Pinned nixpkgs

The infrastructure for using a pinned version of nixpkgs is included but not currently in use. I am awaiting the merging of a couple Pull Requests critical to having the turtlesim example work on macOS.