Build a ROS workspace

In this example, we will show how to deal with a standard ROS development workflow, where the dependencies are backed by nix.

Define which repos you want to manually build

We will split the whole dependency tree in two distinct sets: the source repositories you will manually build for your development, and those which will be handled by nix.

Note

The limitiation here is that we should not have any package in the second set that depend on any package from the first :)

One usual way of defining multiple repositories in the ROS community is with this eg. agimus.repos yaml file:

repositories:
  agimus-controller:
    type: git
    url: https://github.com/agimus-project/agimus-controller
    version: main
  agimus-demos:
    type: git
    url: https://github.com/agimus-project/agimus-demos
    version: main
  agimus-msgs:
    type: git
    url: https://github.com/agimus-project/agimus-msgs
    version: main
  linear-feedback-controller:
    type: git
    url: https://github.com/loco-3d/linear-feedback-controller
    version: main
  linear-feedback-controller-msgs:
    type: git
    url: https://github.com/loco-3d/linear-feedback-controller-msgs
    version: main

Then you can clone all of that in a src directory:

mkdir src
vcs import --input agimus.repos src

Tip

If you don’t already have the vcs program, you can eg.: nix run nixpkgs#vcs2l -- import --input agimus.repos src

Find all the ROS packages in those repositories

Then we can find all the package.xml files in our src dir, look for the name key, and format that for nix:

fd package.xml src -x xq .package.name | tr _ - | sort -u

Tip

If you don’t already have the wonderful fd and/or xq available: nix shell nixpkgs#{fd,xq} --command fd package.xml src -x xq .package.name | tr _ - | sort -u

Write your flake

Now you can create a flake.nix:

{
  description = "example flake for agimus demos with flakoboros";
  inputs.gepetto.url = "github:gepetto/nix";
  outputs =
    inputs:
    inputs.gepetto.lib.mkFlakoboros inputs (
      { lib, ... }:
      {
        rosDistros = [ # We don't have kilted/rolling on those packages yet
          "humble"
          "jazzy"
        ];
        rosShellDistro = "humble"; # rolling would be the default without this
        extraDevRosPackages = [ # Put here the list you got at the previous step
          "agimus-controller"
          "agimus-controller-ros"
          "agimus-demo-00-franka-controller"
          "agimus-demo-01-lfc-alone"
          "agimus-demo-02-simple-pd-plus"
          "agimus-demo-02-simple-pd-plus-tiago-pro"
          "agimus-demo-03-mpc-dummy-traj"
          "agimus-demo-03-mpc-dummy-traj-tiago-pro"
          # "agimus-demo-04-dual-arm-tiago-pro"
          "agimus-demo-04-visual-servoing"
          "agimus-demo-05-pick-and-place"
          "agimus-demo-06-regrasp"
          # "agimus-demo-07-deburring"
          "agimus-demo-08-collision-avoidance"
          "agimus-demos"
          "agimus-demos-common"
          "agimus-demos-controllers"
          "agimus-msgs"
          "linear-feedback-controller"
          "linear-feedback-controller-msgs"
        ];
      }
    );
}

Warning

Work in progress: demos 04 and 07 must be commented for now

Activate your development shell

The standard nix way here is nix develop: it will start a bash shell with everything you need to continue.

But if you want something a bit more comfortable, you can set up nix-direnv. Once this is done, auto-activating the nix develop in the current folder by adjusting environment variables instead of spawning a new shell can be achieved with:

echo 'use flake .' > .envrc
direnv allow

Build your packages

colcon build

Enable the new prefix

This is automatically done on entering nix develop if install/setup.bash exists, but before the first compilation that was not the case. Therefore, for this time only, you should probably:

source install/setup.bash

Profit

ros2 launch agimus_demo_03_mpc_dummy_traj bringup.launch.py use_gazebo:=true use_rviz:=true

Switch ros distro ?

Time to change ROS distro, like upgrade from humble to jazzy ? Sure :)

Remember that rosShellDistro = "humble"; ? It means that by default, nix develop . / use flake . will be equivalent to nix develop .#ros-humble / use flake .#ros-humble.

Obviously, you can therefore use .#ros-jazzy in this example:

rm -rf build install
echo 'use flake .#ros-jazzy' > .envrc # or 'nix develop .#ros-jazzy'
direnv allow
colcon build
source install/setup.bash
ros2 launch agimus_demo_03_mpc_dummy_traj bringup.launch.py use_gazebo:=true use_rviz:=true