Load a single package from a fork of nixpkgs

Help
1

I’m currently moving from channels to flakes and would like to be able to import a package from a fork of NixOS/nixpkags (being modified prior to being updated). However I’m not able to figure out the magic incantation.

akgrant43 is the forked nixpkgs repository. The derivation is at pkgs/development/tools/glamoroustoolkit, and is listed in all-packages.nix.

I’ve tried multiple different combinations based on earlier posts from here (discourse) and StackOverflow, but no luck. My latest attempt is following Getting inputs to modules in a nix-flake with the following:

{
  description = "akg laptop configuration";

  inputs = {
    nixpkgs = {
      url = "github:NixOS/nixpkgs/release-23.05";
    };

    nixos-hardware = {
      url = "github:NixOS/nixos-hardware/master";
    };

    akgrant43 = {
      url = "github:akgrant43/nixpkgs/main";
    };
  };

  # Outputs can be anything, but the wiki + some commands define their own
  # specific keys. Wiki page: https://nixos.wiki/wiki/Flakes#Output_schema
  outputs = { self, nixpkgs, nixos-hardware, akgrant43 }@inputs: {
    nixosConfigurations = {
      akg230611 = inputs.nixpkgs.lib.nixosSystem {
        system = "x86_64-linux";
	specialArgs = { inherit inputs; };
        modules = [
          nixos-hardware.nixosModules.dell-precision-3541
          ./configuration.nix
        ];
      };
    };
  };
}

configuration.nix is fairly long, but the relevant piece is:

{ config, pkgs, inputs, ... }:

{
# snip

  environment.systemPackages = [
    inputs.akgrant43.packages.${pkgs.system}.glamoroustoolkit
  ];

# snip
}

which results in:

error: attribute 'packages' missing

       at /nix/store/knp8yhr6zfl2c96lx2vw7sw1cwd1b6v1-source/akg230611/nixos/configuration.nix:133:5:

          132|   environment.systemPackages = [
          133|     inputs.akgrant43.packages.${pkgs.system}.glamoroustoolkit
             |     ^
          134|   ];
(use '--show-trace' to show detailed location information)

What am I doing wrong?

Thanks,
Alistair

2

Naturally the guide I followed AFTER posting was the one that worked (about the 10 attempt):

See Importing packages from multiple channels in the Flakes wiki page.