alt Hacker NewsAs a Nix evangelist, I have to say: Nix is really not capable of replacing languag-specific package managers.
> running arbitrary commands to invoke language-specific package managers.
This is exactly what we do in Nix. You see this everywhere in nixpkgs.
What sets apart Nix from docker is not that it works well at a finer granularity, i.e. source-file-level, but that it has real hermeticity and thus reliable caching. That is, we also run arbitrary commands, but they don't get to talk to the internet and thus don't get to e.g. `apt update`.
In a Dockerfile, you can `apt update` all you want, and this makes the build layer cache a very leaky abstraction. This is merely an annoyance when working on an individual container build but would be a complete dealbreaker at linux-distro-scale, which is what Nix operates at.
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Well, arbitrary granularity is possible with Nix, but the build systems of today simply do not utilise it. I've for example written an experimental C build system for Nix which handles all compiler orchestration and it works great, you get minimal recompilations and free distributed builds. It would be awesome if something like this was actually available for major languages (Rust?). Let me know if you're working on or have seen anything like this!
Fundamentally speaking, the key point is really just hermeticity and reliable caching. Running arbitrary commands is never the problem anyways. What makes gcc a blessed command but the compiler for my own language an "arbitrary" command anyways?
And in languages with insufficient abstraction power like C and Go, you often need to invoke a code generation tool to generate the sources; that's an extremely arbitrary command. These are just non-problems if you have hermetic builds and reliable caching.