standalone: Expose options

This can be used to teach `nixd` about NixVim options.

docs/modules/standalone.md

@@ -55,3 +55,16 @@ The `config` used to produce a standalone nixvim derivation can be accessed as a
 
 This may be useful if you want unrelated parts of your NixOS or home-manager configuration to use the same value as something in your nixvim configuration.
 
+## Accessing nixvim options
+
+Given a nixvim derivation it is possible to access the module options using `<derivation>.options`.
+This can be useful to configure `nixd` for example:
+
+```nix
+plugins.lsp.servers.nixd = {
+    enable = true;
+    settings = {
+        options.nixvim.expr = ''(builtins.getFlake "/path/to/flake").packages.${system}.neovimNixvim.options'';
+    };
+};
+```

wrappers/standalone.nix

@@ -44,7 +44,8 @@ let
   mkNvim =
     mod:
     let
-      config = handleAssertions (mkEval mod).config;
+      evaledModule = mkEval mod;
+      config = handleAssertions evaledModule.config;
     in
     (pkgs.symlinkJoin {
       name = "nixvim";
@@ -56,6 +57,7 @@ let
     })
     // {
       inherit config;
+      inherit (evaledModule) options;
       nixvimExtend =
         extension:
         mkNvim {