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CONTRIBUTING.md

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Contributing

Contributions should be made via pull requests. Pull requests will be reviewed by one or more maintainers and merged when acceptable.

Consider upstreaming anything that is not specific to nix-ninja to reduce the amount that needs to be maintained in this repository.

Project Structure

The implementation is split into five crates:

  1. nix-libstore: Core Nix data structures
  • Want to use nix-compat from [snix] but they only support Nix 2.3 which doesn't include content-addressed derivations and dynamic derivations.
  1. nix-tool: Helper to spawn Nix commands
  • In the future, we can try generating derivations without depending on recursive nix by implementing nix store add and nix derivation add in Rust.
  1. deps-infer: Dependency inference for C/C++
  • Ninja depends on gcc to infer header includes but in Nix we need to know explicitly all the header inputs upfront.
  • Parses all the include flags from the ninja build rule
  • BFS scans in threads for an include regex to infer header includes
  • Will include more headers than gcc because we match everything instead of processing ifdef, etc.
  1. nix-ninja-task: Nix derivation builder for nix-ninja
  • Since our generated derivations don't depend on stdenv.mkDerivation it is easier to maintain a builder as a Rust binary.
  • Prepares the source directory, runs the ninja build rule, and copies build outputs into Nix placeholders.
  1. nix-ninja: Ninja compatible build system using Nix backend
  • Translate Ninja build graph to Nix derivations
  • Generate individual derivations for each build target

Developing locally

Currently, the easiest way to develop nix-ninja is to use nix@d904921 directly as your nix daemon. This way, you can build nix-ninja itself and the examples (e.g. when iterating on nix build .#example-nix) all in one build.

# flake.nix
{
  inputs = {
    nix = {
      url = "github:NixOS/nix?ref=d904921eecbc17662fef67e8162bd3c7d1a54ce0";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  };

  outputs: inputs:
    let
      pkgs = import inputs.nixpkgs {
        system = "x86_64-linux";
        overlays = [ inputs.nix.overlays.default ];
      };

    in {
      # ... NixOS module
      nix.extraOptions = ''
        experimental-features = flakes nix-command dynamic-derivations recursive-nix ca-derivations
      '';
      # ...
    };
}

If there's a good UX way of iterating on nix-ninja in a tmp store and without modifying your main nix, please contribute!

Implementation notes

  • See todo for remaining work.
  • See TODO: comments in code for open questions.