How to "deploy" projects organized with nix for interpreted languages, e.g. R

[telegott]

I'm very new to nix, so please forgive if I haven't grasped all the concepts.
I have a project in an interpreted language, e.g. R. So far I have come up with this flake.nix. I have three modes, test, development, production, with shared and distinct packages.
Now I can do e.g. nix develop .#test and I'm dropped into a shell that has only the correct packages and the APP_ENV environment variable set.
How do I go on from here, obviously I don't only want a development shell but also provide some entry points, e.g. for test a way to run the tests, for production to start a random command that is the entry point.

Ultimately I want to build a docker image from the production set of packages. So far I have a rather peculiar non-nix setup that build two docker images: one base image with all libraries and one that pulls in the base image and slaps the code on top. This way I can greatly reduce CI build times because in most cases I can just pull in the unchanged base image.

I would also be fine to have a setup of regular dockerfiles that internally use nix, orchestrated by shell scripts for now that just install the layers that are necessary, and then have a nix ... entrypoint.

So these are a few questions at the same time, but basically, how do I continue from a development shell to entrypoints for other things like running scripts, and how do I make sure that these scripts don't result in any build work at runtime?

Thanks alot!

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

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        base = with pkgs; [ R ];
        production = base ++ (with pkgs.rPackages; [ box dplyr sf ]);
        test = production ++ (with pkgs.rPackages; [ tinytest ]);
        development = test ++ (with pkgs; [ nixfmt-classic ])
          ++ (with pkgs.rPackages; [ languageserver styler lintr ]);
      in {
        devShells = {
          default = pkgs.mkShell {
            nativeBuildInputs = [ pkgs.bashInteractive ];
            buildInputs = development;
            shellHook = ''
              export APP_ENV="development"
            '';
          };
          test = pkgs.mkShell {
            nativeBuildInputs = [ pkgs.bashInteractive ];
            buildInputs = test;
            shellHook = ''
              export APP_ENV="test"
            '';
          };
          production = pkgs.mkShell {
            nativeBuildInputs = [ pkgs.bashInteractive ];
            buildInputs = production;
            shellHook = ''
              export APP_ENV="production"
            '';
          };
        };
      });
}

[Aleksanaa]

This should probably be asked in NixOS discourse (discourse.nixos.org)

[telegott]

@Aleksanaa thanks, will do!