lib/{vim,neovim}-plugin: installPackage -> packageDecorator

Replace `mkNeovimPlugin`'s `installPackage` parameter with a new
internal module option: `packageDecorator`.

The option is a function that applies some transformation to
`cfg.package`'s value before it is installed.

lib/neovim-plugin.nix

@@ -50,7 +50,6 @@
       extraPlugins ? [ ],
       extraPackages ? [ ],
       callSetup ? true,
-      installPackage ? true,
     }@args:
     let
       namespace = if isColorscheme then "colorschemes" else "plugins";
@@ -104,6 +103,16 @@
                           package
                         ];
                   };
+              packageDecorator = lib.mkOption {
+                type = lib.types.functionTo lib.types.package;
+                default = lib.id;
+                defaultText = lib.literalExpression "x: x";
+                description = ''
+                  Additional transformations to apply to the final installed package.
+                  The result of these transformations is **not** visible in the `package` option's value.
+                '';
+                internal = true;
+              };
             }
             // lib.optionalAttrs hasSettings {
               settings = lib.nixvim.mkSettingsOption {
@@ -129,8 +138,10 @@
               lib.mkMerge (
                 [
                   {
-                    extraPlugins = (lib.optional installPackage cfg.package) ++ extraPlugins;
                     inherit extraPackages;
+                    extraPlugins = extraPlugins ++ [
+                      (cfg.packageDecorator cfg.package)
+                    ];
                   }
                   (lib.optionalAttrs (isColorscheme && (colorscheme != null)) {
                     colorscheme = lib.mkDefault colorscheme;

lib/vim-plugin.nix

@@ -91,15 +91,26 @@
                         package
                       ];
                 };
+            packageDecorator = lib.mkOption {
+              type = lib.types.functionTo lib.types.package;
+              default = lib.id;
+              defaultText = lib.literalExpression "x: x";
+              description = ''
+                Additional transformations to apply to the final installed package.
+                The result of these transformations is **not** visible in the `package` option's value.
+              '';
+              internal = true;
+            };
           } // settingsOption // extraOptions;
 
           config = lib.mkIf cfg.enable (
             lib.mkMerge [
               {
                 inherit extraPackages;
+                extraPlugins = extraPlugins ++ [
+                  (cfg.packageDecorator cfg.package)
+                ];
                 globals = lib.mapAttrs' (n: lib.nameValuePair (globalPrefix + n)) (cfg.settings or { });
-                # does this evaluate package? it would not be desired to evaluate package if we use another package.
-                extraPlugins = extraPlugins ++ lib.optional (cfg.package != null) cfg.package;
               }
               (lib.optionalAttrs (isColorscheme && (colorscheme != null)) {
                 colorscheme = lib.mkDefault colorscheme;

plugins/by-name/treesitter/default.nix

@@ -430,8 +430,6 @@ helpers.neovim-plugin.mkNeovimPlugin {
 
   # NOTE: We call setup manually below.
   callSetup = false;
-  # NOTE: We install cfg.package manually so we can install grammars using it.
-  installPackage = false;
 
   extraConfig = cfg: {
     plugins.treesitter.luaConfig.content =
@@ -455,10 +453,10 @@ helpers.neovim-plugin.mkNeovimPlugin {
 
     extraFiles = mkIf cfg.nixvimInjections { "queries/nix/injections.scm".source = ./injections.scm; };
 
-    extraPlugins = mkIf (cfg.package != null) [
+    # Install the grammar packages if enabled
-      (mkIf cfg.nixGrammars (cfg.package.withPlugins (_: cfg.grammarPackages)))
+    plugins.treesitter.packageDecorator = lib.mkIf cfg.nixGrammars (
-      (mkIf (!cfg.nixGrammars) cfg.package)
+      pkg: pkg.withPlugins (_: cfg.grammarPackages)
-    ];
+    );
 
     extraPackages = [
       cfg.gccPackage