SenchoPens/base16.nix

config.scheme = "${inputs.tt-schemes}/base16/nord.yaml";

We need to explicitly use mkSchemeAttrs function to use the override field of the resulting scheme attrs:

config.scheme = (config.lib.base16.mkSchemeAttrs "${inputs.tt-schemes}/base16/nord.yaml").override {
  scheme = "Now it's my scheme >:]";
  base00 = "000000";  # make background completely black
};

config.scheme = {
  slug = "balsoftheme"; scheme = "Theme by balsoft"; author = "balsoft";
  base00 = "000000"; base01 = "333333"; base02 = "666666"; base03 = "999999";
  base04 = "cccccc"; base05 = "ffffff"; base06 = "e6e6e6"; base07 = "e6e6e6";
  base08 = "bf4040"; base09 = "bf8040"; base0A = "bfbf40"; base0B = "80bf40";
  base0C = "40bfbf"; base0D = "407fbf"; base0E = "7f40bf"; base0F = "bf40bf";
};

source

Achieve this by theming without config.scheme — by calling mkSchemeAttrs:

home-manager.users.sencho.programs.zathura.extraConfig =
  builtins.readFile (config.lib.base16.mkSchemeAttrs inputs.tt-schemes inputs.base16-zathura);

Without importing base16.nix as a module at all:

home-manager.users.sencho.programs.zathura.extraConfig =
  builtins.readFile ((pkgs.callPackage inputs.base16.lib {}).mkSchemeAttrs inputs.tt-schemes inputs.base16-zathura);

Template repositories often define more than one template variation. For example, zathura template repository defines default.mustache (colors only the interface) and recolor.mustache (colors the interface and pdfs).

By default base16.nix uses default.mustache. To use another template, e.g. recolor.mustache:

home-manager.users.sencho.programs.zathura.extraConfig =
  builtins.readFile (config.scheme {
    templateRepo = inputs.base16-zathura; target = "recolor";
  });

Sample use-case: suppose you like zathura's default.mustache template, but want to change the background (default-bg) from base00 to base01.

1. Override the scheme only for zathura:

home-manager.users.sencho.programs.zathura.extraConfig =
  builtins.readFile ((config.scheme.override {
    base00 = config.scheme.base01;
  }) inputs.base16-zathura);

Keep in mind that by doing so you'll change not only default-bg color, but also inputbar-bg, notification-bg, etc.

2. Copy-paste the template and modify it:

home-manager.users.sencho.programs.zathura.extraConfig =
  builtins.readFile (config.scheme { template = ''
    ... 
    set default-bg   "#{{base01-hex}}"  # <-- we changed this
    set default-fg   "#{{base01-hex}}"

    set statusbar-fg "#{{base04-hex}}"
    set statusbar-bg "#{{base02-hex}}"
    ...
  ''; });

The most probable reason of such an error is incorrectly parsed YAML file of either a scheme or a template.

Fix incorrectly parsed YAML file

• Enable IFD (but beware of a possible error described below): If the problem is in the scheme YAML file, set the scheme as such:

  config.scheme =  {
    yaml = "${inputs.tt-schemes}/base16/nord.yaml";
    use-ifd = "auto";  # to suppress errors, set to "always"
  };

  If the problem is in the template templates/config.yaml file, turn on use-ifd:

  home-manager.users.sencho.programs.zathura.extraConfig =
    builtins.readFile (config.scheme {
      use-ifd = "always";
      templateRepo = inputs.base16-zathura; target = "recolor";
    });

• If you think that it's safe to ignore the error on template instantiation, you can turn off the check:

  home-manager.users.sencho.programs.zathura.extraConfig =
    builtins.readFile (config.scheme {
      check-parsed-config-yaml = false;
      templateRepo = inputs.base16-zathura; target = "recolor";
    });

• If the problem is with a scheme YAML file and the nix evaluates, add the config.scheme.check derivation to your NixOS / home-manager package list, this will indicate which part of the YAML is being parsed incorrectly.
• Submit an issue.
• Fix the YAML upstream. Probable causes: trailing spaces, file structure differs from typical config.yaml / scheme YAML files.
• Fix the Nix parser 😈.

Context: since version v2.0.0 base16.nix parses the YAML file in pure Nix to bypass IFD issues. The parser works for most base16-<scheme-name>.yaml and templates' config.yaml files, but, as YAML can be quite complicated, sometimes they can be parsed incorrectly.

The exact error depends on the point of failure. It will probably be cryptic if incorrect parsing caused an issue during nix evaluation. Otherwise, if your flake evaluates (nix flake check succeeds), the error may look something like this:

error: builder for '/nix/store/snbbfb43qphzfl6xr1mjs0mr8jny66x9-base16-nix-parse-check.drv' failed with exit code 1;
       last 7 log lines:
       > running tests
       > Output of "jd /nix/store/9jvxabhfx9acrysknblg0r2hzvcwv6ab-fromYAML /nix/store/qwmj9cbg7fpi5fvyd2x3kywfbw7hlm8f-parsed-yaml-as-json":
       > @ ["gotcha"]
       > - ["1 2"]
       > + "[ 1 2 ]"
       > Error: /nix/store/qhdqwj0mfp8qn0gq5s95pgd2i57lb09c-source/base16-kandinsky.yaml was parsed incorrectly during nix evaluation.
       > Please consult https://github.com/SenchoPens/base16.nix/tree/main#%EF%B8%8F-troubleshooting

The check that produces this error happens by default for templates by installing a special derivation. You can do it for scheme too by adding the config.scheme.check derivation to your NixOS / home-manager package list, though you might need to set the scheme to { yaml = ...; use-ifd = "auto"; }.

First, check that you have the most recent version of base16.nix. If the error persists, check that you don't set use-ifd anywhere to "auto" or "always".

Relevant issue: #3.

If neither of the above listed solutions do not work for you, please open an issue.