I'm still in the learning process, but one thing I've had a hard time is finding out what functions are available. e.g. there's stdenv.mkDerivation for a generic target, and as your docs mention pythonXY.withPackages for a python virtualenv [1]. But what if I wanted, e.g. Ruby? How do I find out what's available? What options they take?
This is less packaging related (more nix lang related) but here is my go to resource for functions: https://teu5us.github.io/nix-lib.html. teu5us extracted the builtin/lib function docs and put them on one place saving you from having it split up into multiple manuals.
One issue with nix is the content has been written down it’s very inaccessible. It is split up between blog posts, discourse, nixpkgs code comments, the wiki, Reddit, etc. When working on something in nix I’ll frequently have 10+ sources of information. The google-fu needed is strong.
My biggest recommendation is to dive into the nixpkgs repo and other public dotfiles as most likely what you are doing has been done.
https://nix.dev/tutorials/ad-hoc-developer-environments#beyo...