Nix Best Practices

Nix Best Practices

Flake Structure

Standard flake.nix structure:

{
  description = "Project description";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
        };
      in {
        devShells.default = pkgs.mkShell {
          buildInputs = with pkgs; [
            # packages here
          ];
        };
      });
}

Follows Pattern (Avoid Duplicate Nixpkgs)

When adding overlay inputs, use follows to share the parent nixpkgs and avoid downloading multiple versions:

inputs = {
  nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

  # Overlay follows parent nixpkgs
  some-overlay.url = "github:owner/some-overlay";
  some-overlay.inputs.nixpkgs.follows = "nixpkgs";

  # Chain follows through intermediate inputs
  another-overlay.url = "github:owner/another-overlay";
  another-overlay.inputs.nixpkgs.follows = "some-overlay";
};

All inputs must be listed in outputs function even if not directly used: