Zombie Zen

zb: A Build System Prototype

By Roxy Light

In my previous blog post, I talked about some of the shortcomings of Nix as a project and what I wish to see exist in its stead. Since I published the blog post, there have been some promising developments: a constitutional assembly has formed, a fork of the Nix interpreter has arisen, and an alternative Nixpkgs ecosystem is beginning to form. I am enheartened that Nix has a potential future, but it is too early to tell how these new efforts will play out.

In the meantime, I prototyped an idea I had kicking around while I wrote the blog post. zb is an experiment in using Lua as an build configuration language while still using the model described in The Purely Functional Software Deployment Model. I am quite pleased with the results. In my view, this is an existence proof for using a more conventional programming language to reduce the onboarding cost of a technology like Nix.

The README has a more in-depth description of what I built, but in short:

  • zb uses a fairly stock Lua 5.4 interpreter, with the notable exception that it includes dependency information in strings, much like the Nix language. Lua’s simple interpreter made it straightforward to add this feature.
  • zb produces .drv files and uses nix-store --realise to build them. This means that zb is fully interoperable with Nix derivations (e.g. using nixpkgs derivations in zb derivations), but also proves that an alternative build backend could be created in the future.
  • zb uses content-addressed builds to enable the shallow build optimization described in Build systems à la carte.
  • I built a source bootstrap that is mostly equivalent to the nixpkgs standard environment by following the live-bootstrap steps. This includes a working GCC, GNU Make, Coreutils, and Automake, among many other common programs. I discovered in this process that this would be the largest time and effort investment. Even after a month, I still haven’t gotten a build that gets to the end of the steps.

I want to share this research prototype in the interest of showing others what is possible in the space, but I’m not planning on developing it to production-readiness. If you have feedback on zb, let me know on the Auxolotl forum, on the zb repository discussions, or privately.

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