lib: provide an "extended lib" to our modules

lib/extend-lib.nix returns a nixpkg's lib extended with our own
helpers.

This is exposed as `helpers.extendedLib`, but when evaluating our
modules it should be assigned to `specialArgs.lib`.

Outside of our modules you must still access our helpers via
`config.lib.nixvim` or `config.lib.nixvim.extendedLib`.

Within helpers' sub-sections, `lib` is the extended lib.

lib/extend-lib.nix

@@ -0,0 +1,11 @@
+# Extends nixpkg's lib with our functions, as expected by our modules
+{ lib, helpers }:
+lib.extend (
+  final: prev: {
+    # Include our custom lib
+    nixvim = helpers;
+
+    # Merge in our maintainers
+    maintainers = prev.maintainers // import ./maintainers.nix;
+  }
+)

lib/helpers.nix

@@ -6,16 +6,20 @@
 }:
 let
   # Used when importing parts of helpers
-  call = lib.callPackageWith { inherit pkgs lib helpers; };
+  call = lib.callPackageWith {
+    # TODO: deprecate/remove using `helpers` in the subsections
+    inherit pkgs helpers;
+    lib = helpers.extendedLib;
+  };
 
   # Build helpers recursively
   helpers = {
     autocmd = call ./autocmd-helpers.nix { };
     builders = call ./builders.nix { };
     deprecation = call ./deprecation.nix { };
+    extendedLib = call ./extend-lib.nix { inherit lib; };
     keymaps = call ./keymap-helpers.nix { };
     lua = call ./to-lua.nix { };
-    maintainers = import ./maintainers.nix;
     neovim-plugin = call ./neovim-plugin.nix { };
     nixvimTypes = call ./types.nix { };
     options = call ./options.nix { };
@@ -78,6 +82,9 @@ let
       wrapVimscriptForLua
       ;
 
+    # TODO: Deprecate this `maintainers` alias
+    inherit (helpers.extendedLib) maintainers;
+
     toLuaObject = helpers.lua.toLua;
   };
 in

tests/test-sources/extended-lib.nix

@@ -0,0 +1,25 @@
+let
+  module =
+    { lib, helpers, ... }:
+    {
+      assertions = [
+        {
+          assertion = lib ? nixvim;
+          message = "lib.nixvim should be defined";
+        }
+        {
+          assertion = lib.nixvim == helpers;
+          message = "lib.nixvim and helpers should be aliases";
+        }
+      ];
+    };
+in
+{
+  top-level = {
+    inherit module;
+  };
+
+  files-module = {
+    files."libtest.lua" = module;
+  };
+}

wrappers/darwin.nix

@@ -27,6 +27,7 @@ in
           darwinConfig = config;
           defaultPkgs = pkgs;
           helpers = config.lib.nixvim;
+          lib = config.lib.nixvim.extendedLib;
         };
         modules = [
           ./modules/darwin.nix

wrappers/hm.nix

@@ -26,6 +26,7 @@ in
           hmConfig = config;
           defaultPkgs = pkgs;
           helpers = config.lib.nixvim;
+          lib = config.lib.nixvim.extendedLib;
         };
         modules = [
           ./modules/hm.nix

wrappers/nixos.nix

@@ -27,6 +27,7 @@ in
           nixosConfig = config;
           defaultPkgs = pkgs;
           helpers = config.lib.nixvim;
+          lib = config.lib.nixvim.extendedLib;
         };
         modules = [
           ./modules/nixos.nix

wrappers/standalone.nix

@@ -31,6 +31,7 @@ let
         ];
         specialArgs = {
           inherit helpers;
+          lib = helpers.extendedLib;
           defaultPkgs = pkgs;
         } // extraSpecialArgs;
       };