My first Nix flake

flake.macos.nix

{
  # https://nix.dev/anti-patterns/language#unquoted-urls
  inputs.nixpkgs.url = "github:NixOS/nixpkgs";

  outputs = { self, nixpkgs, ... }@attrs:
    # https://discourse.nixos.org/t/using-nixpkgs-legacypackages-system-vs-import/17462/5
    # https://discourse.nixos.org/t/recommendations-for-use-of-flakes-input-follows/17413
    let pkgs = nixpkgs.legacyPackages.aarch64-darwin;
    in {
      # https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-fmt.html
      formatter.aarch64-darwin = nixpkgs.legacyPackages.aarch64-darwin.nixpkgs-fmt;
      # https://blog.ysndr.de/posts/guides/2021-12-01-nix-shells/#development-environments
      # is 'devShell' (singular) actually wrong?
      # https://nixos.wiki/wiki/Flakes
      # https://ryantm.github.io/nixpkgs/builders/special/mkshell/
      devShells.aarch64-darwin.default = pkgs.mkShell {
        buildInputs = [
          pkgs.hello
          pkgs.poppler_utils
        ];
        shellHook = ''
          echo 'Hi, just testing the shell hook.'
        '';
      };
      # $ nix develop .#foo
      devShells.aarch64-darwin.foo = pkgs.mkShell {
        buildInputs = [
          pkgs.hello
        ];
        shellHook = ''
          echo 'Hi, just testing the shell hook (foo version).'
          echo 'Try using pdf2cairo!'
        '';
      };
    };
  nixConfig = {
    # https://nixos.wiki/wiki/Flakes#Setting_the_bash_prompt_like_nix-shell
    # bash-prompt-prefix = "[develop] ";
    bash-prompt = "[develop] ";
  };
}

flake.nix

{
  # https://nix.dev/anti-patterns/language#unquoted-urls
  inputs.nixpkgs.url = "github:NixOS/nixpkgs";

  outputs = { self, nixpkgs, ... }@attrs:
    # https://discourse.nixos.org/t/using-nixpkgs-legacypackages-system-vs-import/17462/5
    # https://discourse.nixos.org/t/recommendations-for-use-of-flakes-input-follows/17413
    let pkgs = nixpkgs.legacyPackages.x86_64-linux;
    in {
      # https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-fmt.html
      formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.nixpkgs-fmt;
      # https://blog.ysndr.de/posts/guides/2021-12-01-nix-shells/#development-environments
      # is 'devShell' (singular) actually wrong?
      # https://nixos.wiki/wiki/Flakes
      # https://ryantm.github.io/nixpkgs/builders/special/mkshell/
      devShells.x86_64-linux.default = pkgs.mkShell {
        buildInputs = [
          pkgs.hello
        ];
        shellHook = ''
          echo 'Hi, just testing the shell hook.'
        '';
      };
      # $ nix develop .#foo
      devShells.x86_64-linux.foo = pkgs.mkShell {
        buildInputs = [
          pkgs.hello
        ];
        shellHook = ''
          echo 'Hi, just testing the shell hook (foo version).'
        '';
      };
    };
  nixConfig = {
    # https://nixos.wiki/wiki/Flakes#Setting_the_bash_prompt_like_nix-shell
    bash-prompt-prefix = "[develop] ";
  };
}