flake: refactor package

- loads init.lua directly,
  before it loads a lua file -> vimscript (`customRC`) -> init.lua

- split the wrapper into its own package,
  makes `src` and `runtimeDeps` overridable

- inherit args into `makeNeovimConfig`,
  makes e.g. `vimAlias` in `wrapNeovimUnstable` work

flake.nix

@@ -22,9 +22,7 @@
       inherit (inputs.nixpkgs) lib;
       pkgs = inputs.nixpkgs.legacyPackages.${system};
       treefmtEval = inputs.treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
-    in {
-      ### nix {run,shell,build}
-      packages.default = let
+
       runtimeDeps = with pkgs; [
         # mason / tree-sitter
         gcc
@@ -35,20 +33,13 @@
         ripgrep
         fd
       ];
-
       src = lib.fileset.toSource {
         fileset = lib.fileset.fileFilter (file: file.hasExt "lua") ./.;
         root = ./.;
       };
-      in
-        pkgs.wrapNeovimUnstable pkgs.neovim-unwrapped
-        (pkgs.neovimUtils.makeNeovimConfig {
-            customRC = ''
-              set runtimepath^=${src}
-              source ${src}/init.lua
-            '';
-          }
-          // {wrapperArgs = ["--prefix" "PATH" ":" "${lib.makeBinPath runtimeDeps}"];});
+    in {
+      ### nix {run,shell,build}
+      packages.default = pkgs.callPackage ./package.nix {inherit runtimeDeps src;};
 
       ### nix fmt
       formatter = treefmtEval.config.build.wrapper;

package.nix

@@ -0,0 +1,18 @@
+{
+  lib,
+  wrapNeovimUnstable,
+  neovim-unwrapped,
+  neovimUtils,
+  runtimeDeps ? null,
+  src ? null,
+  ...
+} @ args:
+wrapNeovimUnstable neovim-unwrapped (neovimUtils.makeNeovimConfig args
+  // {
+    # FIXME: append instead of override the entire wrapperArgs
+    wrapperArgs = ["--prefix" "PATH" ":" "${lib.makeBinPath runtimeDeps}"];
+    luaRcContent = ''
+      vim.cmd [[set runtimepath^=${src}]]
+      ${builtins.readFile "${src}/init.lua"}
+    '';
+  })