Minimal example of YAML as flake output

flake.nix

# Copyright 2024 Google LLC.
# SPDX-License-Identifier: Apache-2.0
{
  description = "Demo of generating a YAML file as a flake output";
  outputs = { self, nixpkgs }: let
    forAllSystems = nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed;
  in {
    packages = forAllSystems (system:
      let pkgs = nixpkgs.legacyPackages.${system};
    in {
      default = (pkgs.formats.yaml { }).generate "foobar.yaml" { foo = "bar"; };
    });
  };
}