Defining pkgs

Default pkgs instance

By default, a pkgs instance (provided as input of perSystem) will be defined from flakoboros nixpkgs input, plus several overlays:

• flakoboros inputs.nix-ros-overlay.overlays.default
• the overlays config option
• the current flake overlays.flakoboros, which is built as described in Controlling overlay-flakoboros

You can control its configuration via nixpkgsConfig option.

Opt-out

If you don’t want this instance, you can set the pkgs config option to false.

Extends

The extends config option provide other pkgs instances (also available as input of perSystem).

In that config option, for each key name, a pkgs-${name} is defined as the pkgs instance from above plus the overlay provided as value.

This overlay is also exposed in the current flake overlays, for reference from other flakes.

Then, the current flake packages output gets a new pkgs-${name} env, similar to the default one, but from that pkgs instance. All other packages are also exposed as passthru of that pkgs-${name} env.

And finally, the current flake devShells also get a pkgs-${name} version of its default.

For example:

{
  pyOverrideAttrs.eigenpy = {
    src = lib.cleanSource ./.;
  };
  extends.eigen5 = final: _prev: {
    eigen = final.eigen_5;
  };
}

will define:

$ nix flake show

├───devShells
│   └───x86_64-linux
│       ├───default: development environment 'flakoboros-default-devShell'
│       └───pkgs-eigen5: development environment 'flakoboros-default-devShell'
├───overlays
│   ├───eigen5: Nixpkgs overlay
│   └───flakoboros: Nixpkgs overlay
└───packages
    └───x86_64-linux
        ├───default: package 'ros-env'
        ├───pkgs-eigen5: package 'ros-env'
        └───py-eigenpy: package 'python3.13-eigenpy-3.12.0'

So you can nix develop (or nix-direnv):

• . to get all dependencies to build the package with eigen 3
• .#pkgs-eigen5 to get all dependencies to build the package with eigen 5

And you can nix build:

• .#py-eigenpy: the package (built with eigen 3)
• .#pkgs-eigen5.py-eigenpy: the package (built with eigen 5)
• .: an env with the package (built with eigen 3)
• .#pkgs-eigen5: an env with the package (built with eigen 5)

With that, you can check everything in CI with eg.:

jobs:
  build:
    runs-on: "${{ matrix.os }}"
    strategy:
      matrix:
        os: ["ubuntu-24.04", "ubuntu-24.04-arm", "macos-26-intel", "macos-26"]
        extends: ["", "pkgs-eigen5"]
    steps:
      - uses: actions/checkout@v6
      # install nix
      - run: nix build -L ".#${{ matrix.extends }}"