gen-prelude

gen-prelude is the small pure-utility dependency that lets the pure gen substrate drop nixpkgs.lib entirely. builtins re-exports plus the list, attrset, and string helpers the rest of the roster needs, vendored behaviour-identically from nixpkgs.lib so nothing downstream has to carry it.

The problem it owns: every gen library needs map, filter, unique, genAttrs — the handful of combinators that make Nix bearable — without pulling in the whole of nixpkgs to get them. gen-prelude is that handful, and nothing more.

It is the one leaf every other member of the roster reaches, directly or transitively: gen-aspects, gen-bind, gen-class, gen-dispatch, gen-graph, gen-inspect, gen-link, gen-memo, gen-merge, gen-product, gen-schema, gen-scope, gen-settings, gen-types, and gen-view all declare it as a flake input. gen-prelude itself declares none — it is builtins only.

Take it alone

{
  inputs.gen-prelude.url = "github:sini/gen-prelude";

  outputs = { gen-prelude, ... }:
    let
      prelude = gen-prelude.lib;
    in
    {
      example = prelude.genAttrs [ "a" "b" ] (n: n + "!");
      # => { a = "a!"; b = "b!"; }
    };
}

No nixpkgs input, no .lib { } functor call — the flake output is a plain value. Without flakes, import ./path/to/gen-prelude/lib gets you the same attrset directly.