Clarify how to define full (non-useHostStore) image contents?

[srd424]

Dipping my toes into arion today and already confused! The minimal example works with useHostStore = true, but without it the generated image does not contain either python or the nix manual:

webapp-webserver-1[402022]: sh: line 1: cd: /nix/store/fc2i53vzn7j3lp5lidj4hm9b9cx9rn99-nix-2.18.5-doc/share/doc/nix/manual: No such file or directory
webapp-webserver-1[402022]: sh: line 2: /nix/store/pfv4raslwhi3101k342752v65zxkwrxq-python3-3.11.9/bin/python: No such file or directory

The flake example explicitly sets image.contents but that doesn't seem to be documented, and I'm unclear exactly what is needed - at the very least it looks like it might involve a fair amount of boilerplate?

[srd424]

The following seems to more or less work, not sure why I need to use image.command instead of service.command. Perhaps in the "non-full NixOS" case service.command could be automatically written into the store to allow dependency resolution to work for image building? (I'm not going to pretend my Nix skills are up to crafting a patch for that..)

{ pkgs, ... }:
let
  cmd = pkgs.writeScriptBin "start" ''
#!${pkgs.bash}/bin/bash
cd "$WEB_ROOT"
${pkgs.python3}/bin/python -m http.server
'';
in {
  project.name = "webapp";
  services = {

    webserver = {
      image.enableRecommendedContents = true;
#      service.useHostStore = true;
      image.contents = [ cmd ];
      image.command = [ "${cmd}/bin/start" ];
#      service.command = [ "${cmd}/bin/start" ];
      service.ports = [
        "8000:8000" # host:container
      ];
      service.environment.WEB_ROOT = "${pkgs.nix.doc}/share/doc/nix/manual";
      service.stop_signal = "SIGINT";
    };
  };
}

[srd424]

Oh, this is simpler:

{ pkgs, ... }:
{
  project.name = "webapp";
  services = {

    webserver = {
      image.enableRecommendedContents = true;
#      service.useHostStore = true;
      image.command = [ "sh" "-c" ''
                  cd "${pkgs.nix.doc}/share/doc/nix/manual"
                  ${pkgs.python3}/bin/python -m http.server
                '' ];
      service.ports = [
        "8000:8000" # host:container
      ];
#      service.environment.WEB_ROOT = "${pkgs.nix.doc}/share/doc/nix/manual";
      service.stop_signal = "SIGINT";
    };
  };
}