flakelight/README.md

Flakelight

A modular Nix flake framework for simplifying flake definitions.

Goals

• Minimize boilerplate needed for flakes
• Support straightforward configuration of all vanilla flake attributes
• Allow sharing common configuration using modules
• What can be done automatically, should be
• Provide good defaults, but let them be changed/disabled

Features

• Handles generating per-system attributes
• Extensible using the module system
• Given package definitions, generates package and overlay outputs
• Automatically import attributes from nix files in a directory (default ./nix)
• Builds formatter outputs that can format multiple file types
• Provides outputs/perSystem options for easy migration

Documentation

See the API docs for available options and example usage.

Additional modules

The following modules are also available:

• flakelight-rust for Rust projects
• flakelight-zig for Zig projects
• flakelight-elisp for flakes providing Emacs lisp package(s)
• flakelight-darwin for nix-darwin configs

Contact

Feel free to ask for help or other questions in the issues/discussions, or reach out on Matrix at #flakelight:nixos.org.

Examples

Shell

The following is an example flake.nix for a devshell, using the passed in nixpkgs. It outputs devShell.${system}.default attributes for each configured system. systems can be set to change configured systems from the default.

{
  inputs.flakelight.url = "github:nix-community/flakelight";
  outputs = { flakelight, ... }:
    flakelight ./. {
      devShell.packages = pkgs: [ pkgs.hello pkgs.coreutils ];
    };
}

With this flake, calling nix develop will make hello and coreutils available.

To use a different nixpkgs, you can instead use:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    flakelight.url = "github:nix-community/flakelight";
  };
  outputs = { flakelight, ... }@inputs:
    flakelight ./. {
      inherit inputs;
      devShell.packages = pkgs: [ pkgs.hello pkgs.coreutils ];
    };
}

Rust package

The following is an example flake for a Rust project using flakelight-rust, invoked by using flakelight-rust's wrapper. Package metadata is taken from the project's Cargo.toml.

{
  inputs.flakelight-rust.url = "github:accelbread/flakelight-rust";
  outputs = { flakelight-rust, ... }: flakelight-rust ./. { };
}

The above flake exports the following:

• Per-system attributes for default systems (x86_64-linux and aarch64-linux)
• packages.${system}.default attributes for each system
• overlays.default providing an overlay with the package (built with the applied pkg set's dependencies)
• devShells.${system}.default that provides rust-analyzer, cargo, clippy, rustc, and rustfmt as well as sets RUST_SRC_PATH
• checks.${system}.${check} attributes for build, test, clippy, and formatting checks
• formatter.${system} with additional support for formatting Rust files

Equivalently, you can just import the flakelight-rust module as follows:

{
  inputs = {
    flakelight.url = "github:nix-community/flakelight";
    flakelight-rust.url = "github:accelbread/flakelight-rust";
  };
  outputs = { flakelight, flakelight-rust, ... }: flakelight ./. {
    imports = [ flakelight-rust.flakelightModules.default ];
  };
}

See flakelight-rust.nix to see how you could configure it without the module.

C application

The following example flake is for a C project with a simple make setup.

{
  description = "My C application.";
  inputs.flakelight.url = "github:nix-community/flakelight";
  outputs = { flakelight, ... }:
    flakelight ./. {
      license = "AGPL-3.0-or-later";

      package = { stdenv, defaultMeta }:
        stdenv.mkDerivation {
          name = "hello-world";
          src = ./.;
          installPhase = ''
            runHook preInstall
            make DESTDIR=$out install
            runHook postInstall
          '';
          meta = defaultMeta;
        };

      devShell.packages = pkgs: with pkgs; [ clang-tools coreutils ];

      formatters = {
        "*.h" = "clang-format -i";
        "*.c" = "clang-format -i";
      }
    };
}

This flake exports the following:

• Per-system attributes for default systems (x86_64-linux and aarch64-linux)
• packages.${system}.default attributes for each system, with license and description set
• overlays.default providing an overlay with the package (built with the applied pkg set's dependencies)
• devShells.${system}.default that provides clang-tools and coreutils
• checks.${system}.${check} attributes for build and formatting checks.
• formatter.${system} with additional support for formatting c and h files with clang-format

C application using autoloads

The above example can instead use the autoload directory feature for the package like the following. Most attributes can be autoloaded.

./flake.nix:

{
  description = "My C application.";
  inputs.flakelight.url = "github:nix-community/flakelight";
  outputs = { flakelight, ... }:
    flakelight ./. {
      license = "AGPL-3.0-or-later";

      devShell.packages = pkgs: with pkgs; [ clang-tools coreutils ];

      formatters = {
        "*.h" = "clang-format -i";
        "*.c" = "clang-format -i";
      }
    };
}

./nix/packages/_default.nix:

{ stdenv, defaultMeta }:
stdenv.mkDerivation {
  name = "hello-world";
  src = ./.;
  installPhase = ''
    runHook preInstall
    make DESTDIR=$out install
    runHook postInstall
  '';
  meta = defaultMeta;
}

A leading underscore in filename is stripped (default needs to be escaped to not conflict with dir import).

Related Resources

• Comparison to flake-parts