neovim-flake/docs/manual/hacking/additional-plugins.md

Adding Plugins

To add a new neovim plugin, first add the source url in the inputs section of flake.nix with the prefix plugin-

{
  inputs = {
    # ...
    plugin-neodev-nvim = {
      url = "github:folke/neodev.nvim";
      flake = false;
    };
    # ...
  };
}

The addition of the plugin- prefix will allow neovim-flake to autodiscover the input from the flake inputs automatically, allowing you to refer to it in areas that require a very specific plugin type as defined in lib/types/plugins.nix

You can now reference this plugin using its string name, the plugin will be built with the name and source URL from the flake input, allowing you to refer to it as a string.

config.vim.startPlugins = ["neodev-nvim"];

Modular setup options

Most plugins is initialized with a call to require('plugin').setup({...}).

We use a special function that lets you easily add support for such setup options in a modular way: mkPluginSetupOption.

Once you have added the source of the plugin as shown above, you can define the setup options like this:

# in modules/.../your-plugin/your-plugin.nix

{lib, ...}:
let
  inherit (lib.types) bool int;
  inherit (lib.nvim.types) mkPluginSetupOption;
in {
  options.vim.your-plugin = {
    setupOpts = mkPluginSetupOption "plugin name" {
      enable_feature_a = mkOption {
        type = bool;
        default = false;
        # ...
      };

      number_option = mkOption {
        type = int;
        default = 3;
        # ...
      };
    };
  };
}

# in modules/.../your-plugin/config.nix
{lib, config, ...}:
let
  cfg = config.vim.your-plugin;
in {
  vim.luaConfigRC = lib.nvim.dag.entryAnywhere ''
    require('plugin-name').setup(${lib.nvim.lua.toLuaObject cfg.setupOpts})
  '';
}

This above config will result in this lua script:

require('plugin-name').setup({
  enable_feature_a = false,
  number_option = 3,
})

Now users can set any of the pre-defined option field, and can also add their own fields!

# in user's config
{
  vim.your-plugin.setupOpts = {
    enable_feature_a = true;
    number_option = 4;
    another_field = "hello";
    size = { # nested fields work as well
      top = 10;
    };
  };
}

Details of toLuaObject

As you've seen above, toLuaObject is used to convert our nix attrSet cfg.setupOpts, into a lua table. Here are some rules of the conversion:

1. nix null converts to lua nil
2. number and strings convert to their lua counterparts
3. nix attrSet/list convert into lua tables
4. you can write raw lua code using lib.generators.mkLuaInline. This function is part of nixpkgs.

Example:

vim.your-plugin.setupOpts = {
  on_init = lib.generators.mkLuaInline ''
    function()
      print('we can write lua!')
    end
  '';
}