flake.nix

{
  description = "latte PoC";

  outputs =
    {
      nixpkgs,
      ...
    }:
    let
      inherit (nixpkgs) lib;
      eachSystem =
        fn: lib.genAttrs lib.systems.flakeExposed (system: fn nixpkgs.legacyPackages.${system});
    in
    {
      latte = eachSystem (pkgs: {
        default = {
          gen =
            args:
            pkgs.linkFarm "template" {
              "flake.nix" = ./flake.nix;
              "flake.lock" = ./flake.lock;
              text = pkgs.writeText "text" args.text or "no text";
            };
        };
      });
    };

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
  };
}

latte

#!/usr/bin/env bash
set -eu

flake=${1:-.}
if [[ ! $flake =~ ":" ]]; then
  flake=$(realpath $flake)
fi

system=$(nix eval --impure --raw --expr builtins.currentSystem)

cat > /tmp/latte.nix << EOS
let
  flake = builtins.getFlake "${flake}";
in
(flake.latte.${system}.default.gen { text = "hoge"; })
EOS

outPath=$(nix build --no-link --print-out-paths --file /tmp/latte.nix)
cd $outPath
rm -rf /tmp/latte
mkdir -p /tmp/latte
find -L . -type f | sort | while read path; do
  mkdir -p $(dirname /tmp/latte/$path)
  cat $path > /tmp/latte/$path
  echo Wrote $path
done