I expect my main hurdle will be stuff that isn’t in NicPkgs. Especially for dev stuff, I’m going to want to pull in low-profile GitHub stuff or Python packages. What’s the escape hatch to bring those into the dev environment?
The function `pkgs.runCommand` is useful if you just want to run some Bash commands https://nixos.org/manual/nixpkgs/stable/#trivial-builder-run...
The main difference compared to running commands in a normal terminal is that builds are sandboxed, with no network access by default:
- If your commands need to download some particular files, you can have Nix fetch them separately (e.g. using `fetchurl`, `fetchGit`, etc.) and provide them to your commands via env vars. See https://nixos.org/manual/nixpkgs/stable/#chap-pkgs-fetchers
- If you don't know what will be downloaded, or there's no way to run in an 'offline' mode, then you can specify hash for the result (making it a "fixed output derivation"). That will give it network access, and Nix will check that the output matches the given hash for reproducibility (you can just make up a random hash to start with; Nix will reject the result, telling you its hash, which you can copy/paste into the definition :) )
The reasons I like this approach include:
- Bash is familiar/traditional and mostly-compatible with e.g. official install instructions provided by many projects, Stack Overflow answers, blog posts and tutorials, etc.
- Powerful/unrestricted, in case we need to do some fiddling between some steps
- Nix often reveals problems with those familiar/traditional instructions; e.g. if some deeply-nested part of an installer happens to run Python, it will fail if Python wasn't explicitly listed in its dependencies (AKA `buildInputs`). Revealing and fixing such things up-front avoids the "works on my machine" problem.
- Bash commands are often tedious and inflexible; so after writing a few of these we may find ourselves wanting more structure, more reusable parts, etc. which is exactly what the helper functions in Nixpkgs provide (like `pkgs.stdenv.mkDerivation`, `pkgs.pythonPackages.buildPythonApplication`, etc.). In contrastt, starting off with those helper functions can seem overwhelming, and the benefits may be hard to appreciate immediately.
One thing you can do is try the Nix package manager on your Linux or macOS system. -- If it's not in nix, you can just do it the way you did things before.
If you want to try NixOS:
1. Writing a package is only necessary for sharing code.. you can still just have Python, setup a virtual env, & run the program as you would.
2. You could use a tool like Podman or Docker, to run stuff in containers. I've heard stuff like https://github.com/containers/toolbox helps this.
(Among other solutions).