`mkPackageOption` helper with `defaultText`

[MattSturgeon]

Nixpkgs has lib.mkPackageOption (documentation, noogle, source) which takes a "pkgs path" and produces an option with an appropriate default and literalExpression defaultText.

# e.g.
lib.mkPackageOption pkgs "hello" { }
# is like
lib.mkOption {
  type = lib.types.package;
  default = pkgs.hello;
  defaultText = lib.literalExpression "pkgs.hello";
  description = "The hello package to use.";
}

We should use this where possible, and copy the implementation in our nullable version.

We could do this in a non-breaking way by having our nullable helper check the pkg arg type; lists and strings can be pkgs-paths while derivations should be actual packages.

Eventually, we could warn when a derivation is passed in to hunt down any remaining call sites, but I see this more as something that can improve future code rather than something we should be in a hurry to migrate existing code to.

TODO:

• Add support to mkVimPlugin and mkNeovimPlugin
  lib/*-plugins: initial support for lib.mkPackageOption #2139
• Implement fancier support (i.e. adding the option within mkNeovimPlugin, using an imported module)
• Migrate all plugins defaultPackage
• Remove the deprecated helpers (mkPackageOption & mkPluginPackageOption)

[MattSturgeon]

We have two helpers currently.

• mkPluginPackageOption, is also just types.package.
  • Used 93 times accross the codebase
  • Two of those are in mkNeovimPlugin and mkVimPlugin...
  • This function could be replaced with nixpkg's mkPackageOption, or could be a wrapper that sets a custom description.

Details

nixvim/lib/options.nix

Lines 329 to 335 in 56208f9

	mkPluginPackageOption =
	name: default:
	mkOption {
	type = types.package;
	inherit default;
	description = "Which package to use for the ${name} plugin.";
	};

• mkPackageOption is similar, but has a nullOr type.
  • It is currently used 51 times across the codebase.

Details

nixvim/lib/options.nix

Lines 311 to 327 in 56208f9

	mkPackageOption =
	args:
	# A default package is required
	assert args ? default;
	# `name` must be present if `description` is missing
	assert (!args ? description) -> args ? name;
	mkNullOrOption' (
	(filterAttrs (n: _: n != "name") args)
	// {
	type = types.package;
	description =
	args.description or ''
	Which package to use for `${args.name}`.
	Set to `null` to disable its automatic installation.
	'';
	}
	);

EDIT: The nixpkgs function has a nullable = true arg, so both of our helpers can be replaced. The only remaining difference is the description produced, which could be handled by a wrapper function on our end.

EDIT2: It also has an extraDescription arg that is appended to the description. This is probably preferable to having a completely overridden description.