Help with `buildDhallPackage`

Sorry for the cross post but I’m not sure where this belongs.

I’m trying to generate a YAML file from a Dhall expression in Nix. The Dhall file that I pass to dhall-to-yaml is shown below and I will refer to it as “dhall source”

let Alacritty = sha256:c9cf010f9ef1a7da4590d70571c1fa5114743f9096b8387b180bfb02f5cdffb1

let mono = ./mono.dhall with size = 12.0

in  Alacritty.Config::{
    , font = mono
    , shell = Some { program = "/usr/bin/fish", args = [ "-l" ] }
    , colors = ./papercolor.dhall
    , key_bindings = ./keys_common.dhall
  with window.decorations = Alacritty.Window.Decoration.full
  with window.dynamic_padding = True
  with window.padding = { x = +10, y = +10 }

I made sure that everything in the dhall-alacritty dependency has a sha256 for the Dhall Prelude, so that I can use buildDhallPackage to load these things into the cache.

Here’s the Nix code

  sources = import ./nix/sources.nix;
  pkgs = import sources.nixpkgs {};

  prelude = pkgs.dhallPackages.buildDhallPackage {
    name = "dhall-lang-prelude";
    code = "${sources.dhall-lang}/Prelude/package.dhall";

  # Fix in source
  preludeMap = pkgs.dhallPackages.buildDhallPackage {
    name = "dhall-lang-prelude";
    code = "${sources.dhall-lang}/Prelude/Map/Type";

  linux = pkgs.dhallPackages.buildDhallPackage {
    name = "dhall-alacritty";
    code = "${sources.dhall-alacritty}/linux.dhall";
    dependencies = [

  # config = pkgs.dhallPackages.buildDhallPackage {
  #   name = "alacritty_linux";
  #   code = ./src/linux.dhall;
  #   dependencies = [ 
  #     linux
  #   ];
  # };

in derivation {
  name = "alacritty_linux.yml";
  builder = "${pkgs.bash}/bin/bash";
  args = [ ./ ];
  dhalljson = pkgs.haskellPackages.dhall-json;
  coreutils = pkgs.coreutils;
  inherit linux;
  # inherit config;
  src = ./src;
  system = builtins.currentSystem;

The idea is to use that derivation in Home Manager to generate an alacritty.yml file. The problem is that if I uncomment alacritty_linux it complains about missing ./mono.dhall. So in other words, the dhall source file expects other files to be available in the same folder. If I run this file through buildDhallPackage it ends up in the Nix store, without the rest of the sources. But if I comment out the call to buildDhallPackage, my cache doesn’t have the necessary dependencies, it tries to make an HTTP call and that fails for obvious reasons in the Nix builder.

I’m missing a piece of the puzzle here and I don’t know what it is. My idea is that I should uncomment the commented out lines, and then pass inherit config to derivation but while also adding the necessary, local (~ relative) sources to name = "alacritty_linux"

Solved in the linked thread on the Dhall Discourse

1 Like