[matklad]

I am not an expert, but here’s my attempt at a useful comment.

On the highest level, `nix` is an alternative build system. So, if someone packages your app with `nix`, there’s now extra work to keep that working, and it’s on the packager to keep it working. If they packaged your app such that it’s using different dependencies than those required, that’s a bug in the package. As a maintainer, you can help here by making it clearer what versions are accepted, and by making it easier to run the tests for a package.

If we open a black box, there are two things in play here: Nix-the-build-system and nixpkgs package collection.

The build system is very open ended and can specify all dependencies precisely, but it’s on the user to define what that means exactly.

nixpkgs is a coherent collection of nix packages, a bit like a Linux distro. In particular, it _generally_ has one version of each package, and there’s some testing to make sure that all the packages work together.

Now, to package a Python app with Nix you can either pull dependencies from nixpkgs, in which case the situation would be similar to, eg, packaging for Debian.

Or you could create a hermetic environment, where an app gets an isolated copy of dependencies, specific just to the single app, a situation similar to using virtual env.

It sounds like what happened here is that your app got packaged in the fist way, but actually it can work only in the second way. I assume you do specify specific compatible version of Django somewhere, and if a package (be it .deb, .rpm, or .nix) doesn’t respect that, that’s a bug in the package.

Hope this helps!

[SuperSandro2000]

> packaging for Debian.

Not really, nix is way more flexible and more up to date and nix also often runs tests and different pythons cannot interfere with each other that easily. On a high level things are similar but the details are wastly different.

> Or you could create a hermetic environment, where an app gets an isolated copy of dependencies, specific just to the single app, a situation similar to using virtual env.

That could also be done with nix but is often not because upstream pin quality is often lacking.