Nix flake templates

Here are the templates I often use for my projects. They works perfectly with nix develop command and nix-direnv.

Systems

When we start using flake, we must specify which system this flake is targeting to. Honestly I never really care about the targeting system, I am using both Linxu and MacOS, I just want the same flake to be working on all systems.

    allSystems = [
      "x86_64-linux" # 64-bit Intel/AMD Linux
      "aarch64-linux" # 64-bit ARM Linux
      "x86_64-darwin" # 64-bit Intel macOS
      "aarch64-darwin" # 64-bit ARM macOS
    ];

flake-utils is a popular solution to this problem. After reading Why you don't need flake-utils, I've opted to use nix-systems instead.

Templates

Currently I have 4 templates to cover my daily needs.

default / shell

This template generates a flake that enables you to initiate the CLI exclusively for the project. For instance, if I solely require Terraform for my infrastructure projects, I can use this template to launch the opentofu CLI.

nix flake init -t github:liyangau/flake-templates

nur

This template leverages packages accessible from NUR. I've uploaded several packages I use daily onto NUR. With this template, I can easily access the CLI on a per-project basis.

nix flake init -t github:liyangau/flake-templates#nur

local

This template reads a local default.nix file, built the package and create shell environment with the package. It is useful when the package isn't accessible via nixpkgs or NUR. Typically, I use nix-init to generate the default.nix file automatically, which I subsequently integrate into my local project.

nix flake init -t github:liyangau/flake-templates#local

python

This template gives me a shell with Python 3.12 along with certain libraries to my needs.

nix flake init -t github:liyangau/flake-templates#python

unfree App

Sometimes, you might encounter errors similar to the following when attempting to use the flake. This typically occurs due to one of the packages being non-free, such as terraform.

       a) To temporarily allow unfree packages, you can use an environment variable
          for a single invocation of the nix tools.

            $ export NIXPKGS_ALLOW_UNFREE=1

          Note: When using `nix shell`, `nix build`, `nix develop`, etc with a flake,
                then pass `--impure` in order to allow use of environment variables.

       b) For `nixos-rebuild` you can set
         { nixpkgs.config.allowUnfree = true; }
       in configuration.nix to override this.

       Alternatively you can configure a predicate to allow specific packages:
         { nixpkgs.config.allowUnfreePredicate = pkg: builtins.elem (lib.getName pkg) [
             "terraform"
           ];
         }

       c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
         { allowUnfree = true; }
       to ~/.config/nixpkgs/config.nix.

To solve the issue, you need to add config.allowUnfree = true; to forEachSystem as below.

    let
      forEachSystem =
        f:
        nixpkgs.lib.genAttrs (import systems) (
          system:
          f {
            pkgs = import nixpkgs {
              config.allowUnfree = true;
              inherit system;
            };
          }
        );
    in