lib: segregate and deprecate functions that need pkgs

Splits everything that depends on a `pkgs` instance into an optional
attrs, allowing `helpers.nix` to be bootstrapped without `pkgs`.

This required some refactoring:
- `modules.specialArgs` is only available when `pkgs` is used
- `modules.specialArgsWith` now requires `defaultPkgs` be provided
- `builders.*` now have `*With` variants that take `pkgs` as an argument
  and a `withPkgs` function that returns the old interface
- Had to define the fixed part of `builders` outside the attrs for now,
  to avoid infinite recursion.
- The old `builders` are now deprecated, and print a warning when
  evaluated
- `withOptoinalFns` was introduced to merge the optional attrs into the
  final lib.

modules/files.nix

@@ -6,6 +6,8 @@
   ...
 }:
 let
+  builders = lib.nixvim.builders.withPkgs pkgs;
+
   fileTypeModule =
     {
       name,
@@ -73,10 +75,10 @@ let
             then
               if lib.isDerivation config.source then
                 # Source is a derivation
-                helpers.byteCompileLuaDrv config.source
+                builders.byteCompileLuaDrv config.source
               else
                 # Source is a path or string
-                helpers.byteCompileLuaFile derivationName config.source
+                builders.byteCompileLuaFile derivationName config.source
             else
               config.source;
         };

modules/top-level/files/submodule.nix

@@ -3,7 +3,6 @@
   config,
   lib,
   pkgs,
-  helpers,
   ...
 }:
 {
@@ -18,7 +17,8 @@
   config =
     let
       derivationName = "nvim-" + lib.replaceStrings [ "/" ] [ "-" ] name;
-      writeContent = if config.type == "lua" then helpers.writeLua else pkgs.writeText;
+      writeContent =
+        if config.type == "lua" then lib.nixvim.builders.writeLuaWith pkgs else pkgs.writeText;
     in
     {
       path = lib.mkDefault name;

modules/top-level/output.nix

@@ -8,6 +8,7 @@
 let
   inherit (lib) types mkOption mkPackageOption;
   inherit (lib) optional optionalString optionalAttrs;
+  builders = lib.nixvim.builders.withPkgs pkgs;
 in
 {
   options = {
@@ -91,7 +92,7 @@ in
         let
           byteCompile =
             p:
-            (helpers.byteCompileLuaDrv p).overrideAttrs (
+            (builders.byteCompileLuaDrv p).overrideAttrs (
               prev: lib.optionalAttrs (prev ? dependencies) { dependencies = map byteCompile prev.dependencies; }
             );
         in
@@ -223,8 +224,8 @@ in
         config.content
       ];
 
-      textInit = helpers.writeLua "init.lua" customRC;
-      byteCompiledInit = helpers.writeByteCompiledLua "init.lua" customRC;
+      textInit = builders.writeLua "init.lua" customRC;
+      byteCompiledInit = builders.writeByteCompiledLua "init.lua" customRC;
       init =
         if
           config.type == "lua"
@@ -250,7 +251,7 @@ in
             paths = [ config.package ];
             # Required attributes from original neovim package
             inherit (config.package) lua meta;
-            nativeBuildInputs = [ helpers.byteCompileLuaHook ];
+            nativeBuildInputs = [ builders.byteCompileLuaHook ];
             postBuild = ''
               # Replace Nvim's binary symlink with a regular file,
               # or Nvim will use original runtime directory