Nickel-nix

An experimental Nix toolkit to use Nickel as a language for writing nix packages, shells and more.

Caution: nickel-nix is not a full-fledged Nix integration. It is currently missing several basic features. nickel-nix is intended to be a proof-of-concept for writing a Nix derivation using Nickel at the moment, without requiring new features either in Nix or in Nickel. The future of the integration of Nix and Nickel will most probably involve deeper changes to the two projects, and hopefully lead to a more featureful and ergonomic solution.

How to use

We currently provide a few basics development environment for some languages. You need Nix with flakes enabled to use Nickel-nix.

You can list available development shell templates by running:

nix flake show github:nickel-lang/nickel-nix

The following example copies the rust devshell and enters the development environment.

$ mkdir my_project
$ cd my_project
$ nix flake init -t github:nickel-lang/nickel-nix#rust-devshell
$ nix run .#regenerate-lockfile
$ nix develop --impure

Content

This repo is composed of a Nix library, a Nickel library and a flake which provides the main entry point of nickel-nix, the Nix importFromNcl function. This function takes the current directory, a Nickel file and inputs to forward and produces a derivation.

The Nickel library contains in-code documentation that can be leveraged by the nickel query command. For example:

nickel query -f nix.ncl will show the top-level documentation and the list of available symbols
nickel query -f nix.ncl lib.import_file will show the documentation of a specific symbol, here import_file.

Examples

examples/c-hello-world and its variations build a simple hello world program in C.

The previous example of a shell based on mkShell has been removed. Nickel-nix takes the route of re-implementing a modular devshell framework in pure Nickel, relying solely on Nix for derivation. An example of a such basic development shell is planned in a coming pull request.

More examples of varied derivations are to come.