zombiezen build (zb) tool

zb is an experiment in hermetic, reproducible build systems. It is a prototype and should not be used for production purposes.

zb is based on the ideas in The purely functional software deployment model by Eelco Dolstra and Build systems à la carte, as well as the author's experience in working with build systems. The build model is the same as in Nix, but build targets are configured in Lua instead of a domain-specific language.

Examples

The hello world example:

return derivation {
  name    = "hello";
  infile  = path "hello.txt";
  builder = "/bin/sh";
  system  = "x86_64-linux";
  args    = {"-c", "while read line; do echo \"$line\"; done < $infile > $out"};
}

Other examples:

Multi-step builds
stage0-posix/x86_64-linux.lua, which uses the stage0-posix project to build a minimal userspace (including a rudimentary C compiler).
bootstrap.lua, which follows the live-bootstrap project steps to build a more complete userspace.

Getting Started

Install Nix (used as a temporary build backend, see Caveats below)
go build ./cmd/zb
./zb build --file demo/hello.lua

You can use ./zb --help to get more information on commands.

zb uses a slightly modified version of Lua 5.4. The primary difference is that strings (like those returned from the path function or the .out field of a derivation) can carry dependency information, like in the Nix expression language. This is largely hidden from the user. From there, the following libraries are available:

Basic functions
The table module
Additional functions, such as path and derivation. These are intentionally similar to the Nix built-in functions.

Objectives

Prove that Lua is a viable alternative to a domain-specific build language. (Done!)
Exclusively use content-addressed outputs. (Done!) This enables shallow builds, as described in Build systems à la carte.
Establish a source bootstrap that is equivalent to the nixpkgs standard environment. (Partially implemented by following the live-bootstrap steps.)
Permit optional interoperability with the nixpkgs ecosystem. (Not implemented yet: #2)

Caveats

The following is a list of shortcuts taken for the zb prototype.

zb requires Nix to be installed. zb acts as a frontend over nix-store --realise to actually run the builds, but this dependency could be removed in the future.
zb was written in Go for speed of development. This makes self-hosting more complex, but there's nothing preventing a more production-ready implementation in C/C++.
The Lua next and pairs functions should sort keys to be deterministic.
Need to stabilize the Lua standard library that's available. string.format specifically would be good, but would require some fancy work to support the "context" dependency feature.
The stage0 demo is not entirely hermetic, since it uses the host's /bin/sh. Hypothetically, the demo could use the included kaem shell if kaem could support $out expansion.
The derivation built-in does not support the outputs parameter to declare multiple outputs.
In the demo directory, most all derivations are in a single file. A more full standard library would split up files.

License

MIT

zombiezen / zb