How do I add extra packages through extraPackages?

[ex-nix]

What am I doing wrong here?

devShell.extraPackages = [
  git
];

I get the following error:

error: undefined variable 'git'

       at /nix/store/lhr1v8nir1a7ab1xvbrhng2i0r6mvxph-source/flake.nix:28:13:

           27| 	  devShell.extraPackages = [
           28|             git
             |             ^
           29| 	  ];

I'm not sure where I should get the package definition from.

[shanesveller]

Hi there! There is no default source of packages that is automatically in scope, syntactically speaking, so you would need to provide that context in your own flake definition. This can be done via the surrounding syntax constructs, such as function arguments or a let-binding, for example.

You can see more information about the available arguments that flake-parts provides here. I could potentially be more explicit in the README about this, but some amount of practical familiarity with flake-parts will be necessary to be successful with this library, and would potentially benefit your other Nix use anyway.

Adapting the example flake to your question here, you can use the flake-parts perSystem argument to acquire a version of your nixpkgs input that already honors the system being defined. This means you can write pkgs.something and not inputs.nixpkgs.legacyPackages.aarch64-darwin.something:

outputs = inputs @ {
    beam-flakes,
    flake-parts,
    ...
  }:
    flake-parts.lib.mkFlake {inherit inputs;} {
      imports = [beam-flakes.flakeModule];

      systems = ["aarch64-darwin" "x86_64-darwin" "x86_64-linux"];

      perSystem = { pkgs, ... }: {
        beamWorkspace = {
          enable = true;
          # your other settings here ...
          devShell.extraPackages = [ pkgs.git ];
        };
      };
    };

[ex-nix]

Thanks a lot! 😄