plugins/treesitter: allow user to toggle default grammars

modules/plugins/treesitter/config.nix

@@ -5,8 +5,9 @@
   ...
 }: let
   inherit (lib.modules) mkIf mkMerge;
-  inherit (lib.lists) optional;
+  inherit (lib.lists) optional optionals;
   inherit (lib.trivial) boolToString;
+  inherit (lib.nvim.lists) listContainsValues;
   inherit (lib.nvim.binds) mkSetBinding addDescriptionsToMappings;
   inherit (lib.nvim.lua) toLuaObject;
   inherit (lib.nvim.dag) entryBefore entryAnywhere;
@@ -23,6 +24,7 @@ in {
       startPlugins = ["nvim-treesitter"] ++ optional usingNvimCmp "cmp-treesitter";
 
       autocomplete.sources = {"treesitter" = "[Treesitter]";};
+      treesitter.grammars = optionals cfg.addDefaultGrammars cfg.defaultGrammars;
 
       maps = {
         # HACK: Using mkSetLuaBinding and putting the lua code does not work for some reason: It just selects the whole file.
@@ -35,6 +37,7 @@ in {
           (mkSetBinding mappings.incrementalSelection.decrementByNode ":lua require('nvim-treesitter.incremental_selection').node_decremental()<CR>")
         ];
       };
+
       # For some reason treesitter highlighting does not work on start if this is set before syntax on
       configRC.treesitter-fold = mkIf cfg.fold (entryBefore ["basic"] ''
         set foldmethod=expr
@@ -43,7 +46,7 @@ in {
       '');
 
       luaConfigRC.treesitter = entryAnywhere ''
-        require'nvim-treesitter.configs'.setup {
+        require('nvim-treesitter.configs').setup {
           -- Disable imperative treesitter options that would attempt to fetch
           -- grammars into the read-only Nix store. To add additional grammars here
           -- you must use the `config.vim.treesitter.grammars` option.
@@ -51,13 +54,23 @@ in {
           sync_install = false,
           ensure_installed = {},
 
+          -- Indentation module for Treesitter
+          indent = {
+            enable = true,
+            disable = {},
+          },
+
+          -- Highlight module for Treesitter
           highlight = {
             enable = ${boolToString cfg.highlight.enable},
             disable = ${toLuaObject cfg.highlight.disable},
+            additional_vim_regex_highlighting = false,
           },
 
+          -- Indentation module for Treesitter
           incremental_selection = {
             enable = true,
+            disable = {},
             keymaps = {
               init_selection = false,
               node_incremental = false,

modules/plugins/treesitter/treesitter.nix

@@ -4,11 +4,9 @@
   ...
 }: let
   inherit (lib.options) mkOption mkEnableOption literalMD;
+  inherit (lib.types) listOf package str either bool;
   inherit (lib.nvim.binds) mkMappingOption;
-  inherit (lib.types) listOf package str either;
+  inherit (lib.nvim.types) luaInline mkGrammarOption;
-  inherit (lib.nvim.types) luaInline;
-
-  inherit (pkgs.vimPlugins.nvim-treesitter) builtGrammars;
 in {
   options.vim.treesitter = {
     enable = mkEnableOption "treesitter, also enabled automatically through language options";
@@ -37,7 +35,7 @@ in {
     highlight = {
       enable = mkEnableOption "highlighting with treesitter";
       disable = mkOption {
-        type = either (luaInline (listOf str));
+        type = either (listOf str) luaInline;
         default = [];
         example = literalMD ''
           ```lua
@@ -69,20 +67,33 @@ in {
       };
     };
 
+    addDefaultGrammars = mkOption {
+      type = bool;
+      default = true;
+      description = ''
+        Whether to add the default grammars to the list of grammars
+        to install.
+        This option is only relevant if treesitter has been enabled.
+      '';
+    };
+
     defaultGrammars = mkOption {
       internal = true;
       readOnly = true;
       type = listOf package;
-      default = with builtGrammars; [c lua vim vimdoc query];
+      default = with pkgs.vimPlugins.nvim-treesitter.builtGrammars; [c lua vim vimdoc query];
       description = ''
         A list of treesitter grammars that will be installed by default
-        if treesitter has been enabled.
+        if treesitter has been enabled and  {option}`vim.treeesitter.addDefaultGrammars`
+        has been set to true.
 
-        ::: {.warning}
+        ::: {.note}
         Regardless of which language module options you enable, Neovim
         depends on those grammars to be enabled while treesitter is enabled.
-        This list cannot be modified, but its contents will only be appended
+
-        if the list of grammars does not contain the required grammars.
+        This list cannot be modified, but if you would like to bring your own
+        parsers instead of those provided here, you can set `addDefaultGrammars`
+        to false
         :::
       '';
     };