In reply to @daniel:nopemail.org
https://nodejs.org/en/blog/release/v20.6.0

There is built-in support for env files. No need for dotenv

so yeah i guess you could just change the makeWrapper to this:

    makeWrapper ${pkgs.nodejs-slim_20}/bin/node $out/bin/sveltepackage \
      --add-flags --env-file=.env \
      --add-flags $out/lib/node_modules/sveltepackage