iosevka custom build plans on nix

flake.nix

{
  description = "Custom builds of Iosevka";

  inputs = {
    nixpkgs.url     = "nixpkgs/nixpkgs-unstable";
    systems.url = "github:nix-systems/x86_64-linux";
    flake-utils = {
      url = "github:numtide/flake-utils";
      inputs.systems.follows = "systems";
    };
  };

  outputs = { self, nixpkgs, flake-utils, ... }:
    {
      overlays.default = final: prev:
        let
          pkgs = nixpkgs.legacyPackages.${prev.system};
        in {
          inherit (pkgs) iosevka;
          josevka = pkgs.iosevka.overrideAttrs rec { 
            privateBuildPlan = builtins.readFile ./plans/josevka.toml; 
            set = "josevka"; 
          };
          
        };
    } // flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
          overlays = [ self.overlays.default ];
        };
      in {
        packages = {
          inherit (pkgs) iosevka josevka;
        };
        defaultPackage = pkgs.josevka;
      });
}

log.txt

 - system: `"x86_64-linux"`
 - host os: `Linux 5.15.90.1-microsoft-standard-WSL2, Ubuntu, 22.04.3 LTS (Jammy Jellyfish), nobuild`
 - multi-user?: `no`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.13.2`
 - channels(jhilker): `"home-manager, nixpkgs"`
 - nixpkgs: `/home/jhilker/.nix-defexpr/channels/nixpkgs`

plans_josevka.toml

[buildPlans.iosevka-josevka]
family = "Josevka"
spacing = "normal"
serifs = "sans"
export-glyph-names = false
no-cv-ss = true

[buildPlans.iosevka-josevka.variants]
  inherits = "ss03"

  [buildPlans.iosevka-josevka.variants.design]
    capital-j = "serifed-symmetric"
    a = "double-storey-tailed"
    b = "toothed-serifless"
    d = "tailed-serifless"
    f = "flat-hook-serifless-crossbar-at-x-height"
    g = "single-storey-flat-hook-serifless"
    k = "symmetric-touching-serifless"
    q = "tailed-serifless"
    t = "flat-hook-short-neck"
    four = "semi-open-non-crossing"
    dollar = "open"
    percent = "rings-continuous-slash"
    question = "corner"
    cent = "open"

    [buildPlans.iosevka-josevka.variants.italic]
    f = "flat-hook-tailed-crossbar-at-x-height"
    l = "tailed-serifed"
    q = "diagonal-tailed-serifless"


[buildPlans.iosevka-josevka.weights.regular]
shape = 400
menu = 400
css = 400

[buildPlans.iosevka-josevka.weights.bold]
shape = 700
menu = 700
css = 700

[buildPlans.iosevka-josevka.slopes.upright]
angle = 0
shape = "upright"
menu = "upright"
css = "normal"

[buildPlans.iosevka-josevka.slopes.italic]
angle = 9.4
shape = "italic"
menu = "italic"
css = "italic"

[buildPlans.iosevka-josevka.widths.normal]
shape = 550
menu = 5
css = "normal"