lib/modules: add applyExtraConfig

Used for
- mkVimPlugin: extraConfig
- mkNeovimPlugin: extraConfig
- mkLsp: extraConfig
- mkLsp: settings
- mkExtension (telecsope): extraConfig

lib/modules.nix

@@ -36,6 +36,28 @@ in
         helpers = self;
       } // extraSpecialArgs;
     };
+
+  /**
+    Apply an `extraConfig` definition, which should produce a `config` definition.
+    As used by `mkVimPlugin` and `mkNeovimPlugin`.
+
+    The result will be wrapped using a `mkIf` definition.
+  */
+  applyExtraConfig =
+    {
+      extraConfig,
+      cfg,
+      opts,
+      enabled ? cfg.enable or (throw "`enabled` argument not provided and no `cfg.enable` option found."),
+    }:
+    let
+      maybeApply = x: maybeFn: if builtins.isFunction maybeFn then maybeFn x else maybeFn;
+    in
+    lib.pipe extraConfig [
+      (maybeApply cfg)
+      (maybeApply opts)
+      (lib.mkIf enabled)
+    ];
 }
 // lib.mapAttrs (
   name: msg: