nickel-nix VS nickel

Have you tried https://github.com/nickel-lang/nickel-nix ?

I didn't use it yet, but looks like this supposed to do it.

These days those aren't the only options; you can also use Nickel: https://github.com/nickel-lang/nickel-nix

Which isn't fully baked, no, but here's hoping.

One target-use case of Nickel is to be used as an alternative front-end for Nix (instead of Nix expressions). There is a draft RFC and a repository to use Nickel to write development shell (Nixel). The goal is that, one day, you can actually just transparently call to Nix code and into Nixpkgs. Until then, I totally understand that nothing can be the power of levering Nixpkgs... so your approach makes sense :)

Undecided; see https://github.com/nickel-lang/nickel-nix for a proof-of-concept of an integration that requires making no changes to either Nickel or Nix.

So, its key features are:

1. domain-specific: designed for conveniently creating and composing derivations. This reason alone already justifies a new language, or an embedded domain-specific language (such as the Guile/Scheme for guix), or a mix of both (Starlark, the build language of Bazel embedded in a restricted Python-variant).

2. purely functional: this ties well into the philosophical backing of Nix the package manager, which aims to be purely functional, also known as hermeticity in other build systems (Bazel).

3. lazily evaluated: similar to other build systems (including Bazel), so that you can build only what you need on demand.

4. dynamically typed: this one is controversial. Being dynamically typed—in other words, not developing a type system—gets Nix out of the door first. But users often complain about the lack of proper types and modularity. There are experiments to address this, such as Nickel (https://github.com/tweag/nickel).

It is understandable that a one-pager may not have space for the whys.

Nickel：Nickel is a straightforward configuration language aimed at automatically generating static configuration files. Essentially, it's akin to JSON with the addition of functions and types.

Also look at nickel which is an evolution of nix. It's my favorite in this space.

nickel-lang.org

https://github.com/tweag/nickel

Or this https://github.com/tweag/nickel

Nickel is a programming language. While HCL is just a configuration format, so not really comparable.

Here's a comparison with similar tools: https://github.com/tweag/nickel#comparison

As for 'providence', I suppose you meant provenance :) it's been delayed because this was less critical for 1.0 to decide on or to implement (as it: it doesn't break backward compatibility in any way to add this feature in the short term), but this is very much on the roadmap: Issue #235. That's a must-have in a language with merging like Nickel.

Have you considered using a different language for templating? this could be a BIG selling point. Some good ones are cue-lang (though I haven't seen support for rust), kcl or nickel-lang.