plugins/telescope: add support of extensions

modules/plugins/navigation/telescope.nix

@@ -1,14 +1,57 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, pkgs, nix2lua, ... }:
 
-let cfg = config.plugins.navigation.telescope; in
+let
+  inherit (builtins) match isFunction attrValues;
+
+  cfg = config.plugins.navigation.telescope;
+
+  telescopeExtensions = lib.flip lib.filterAttrs pkgs.vimPlugins (k: v:
+    k != "telescope-nvim"
+    && match "^.+[-_]telescope$|^telescope[-_].+$" k == [ ]
+  );
+
+  extensions =
+    if isFunction cfg.extensions then cfg.extensions telescopeExtensions
+    else cfg.extensions;
+
+  extensionOpts = { name, config, ... }: {
+    options = with lib; with types; {
+      name = mkOption {
+        type = str;
+        description = "Extension name";
+      };
+      package = mkPackageOption telescopeExtensions name { };
+      settings = mkOption {
+        type = attrs;
+        default = { };
+      };
+
+      # TODO: add an option to change the way the extension is loaded.
+
+      afterTelescopeSetup = mkOption {
+        type = listOf attrs;
+        readOnly = true;
+        internal = true;
+      };
+    };
+
+    config = {
+      name = lib.mkDefault name;
+
+      afterTelescopeSetup = with nix2lua; lib.optional (config.settings != { })
+        (pipe1 (var config.plugin.telescope-nvim.varName) (call "load_extension" config.name));
+    };
+  };
+
+in
 {
-  options.plugins.navigation.telescope = with lib; {
+  options.plugins.navigation.telescope = with lib; with types; {
     enable = mkEnableOption "telescope";
 
     package = mkPackageOption pkgs.vimPlugins "telescope-nvim" { };
 
     settings = mkOption {
-      type = types.attrs;
+      type = attrs;
       default = { };
       description = ''
         See: https://github.com/nvim-telescope/telescope.nvim?tab=readme-ov-file#customization
@@ -21,15 +64,46 @@ let cfg = config.plugins.navigation.telescope; in
         };
       };
     };
+
+    extensions = mkOption {
+      type = let extSubmodule = attrsOf (submodule extensionOpts); in oneOf [
+        (functionTo (extSubmodule))
+        extSubmodule
+      ];
+      default = { };
+      defaultText = literalExpression "{}";
+      example = {
+        telescope-live-grep-args-nvim = { name = "live_grep_args"; };
+      };
+    };
   };
 
   config = lib.mkIf cfg.enable {
-    plugin.plenary-nvim = lib.mkDefault { isDependency = true; };
+    plugin = lib.mkMerge (lib.flatten [
+      {
+        plenary-nvim = lib.mkDefault { isDependency = true; };
+        telescope-nvim = {
+          name = "telescope";
+          package = cfg.package;
+          setupSettings = lib.mkMerge (lib.flatten [
+            cfg.settings
 
-    plugin.telescope-nvim = {
-      name = "telescope";
-      package = cfg.package;
-      setupSettings = cfg.settings;
-    };
+            (lib.mapAttrsToList
+              (k: v: { extensions."${v.name}" = v.settings; })
+              (lib.filterAttrs (k: v: v.settings != { }) extensions)
+            )
+          ]);
+          afterSetup = lib.flatten (map (ext: ext.afterTelescopeSetup) (attrValues extensions));
+        };
+      }
+
+      # extensions
+      (lib.flip lib.mapAttrsToList extensions (packageName: package: {
+        "${packageName}" = {
+          inherit package;
+          isDependency = lib.mkDefault true;
+        };
+      }))
+    ]);
   };
 }