Allow recursive schemas

Author: danielfriis

README.md

@@ -262,7 +262,7 @@ end
 
 ### Schema Definitions and References
 
-You can define sub-schemas and reference them in other schemas.
+You can define sub-schemas and reference them in other schemas, or reference the root schema to generate recursive schemas.
 
 ```ruby
 class MySchema < RubyLLM::Schema
@@ -281,6 +281,13 @@ class MySchema < RubyLLM::Schema
   object :user do
     reference :location
   end
+
+  # Using a reference to the root schema
+  object :ui_schema do
+    string :element, enum: ["input", "button"]
+    string :label
+    object :sub_schema, reference: :root
+  end
 end
 ```
 

lib/ruby_llm/schema/dsl.rb

@@ -87,7 +87,11 @@ def define(name, &)
       end
 
       def reference(schema_name)
-        {"$ref" => "#/$defs/#{schema_name}"}
+        if schema_name == :root
+          {"$ref" => "#"}
+        else
+          {"$ref" => "#/$defs/#{schema_name}"}
+        end
       end
 
       # Schema building methods

spec/ruby_llm/schema_spec.rb

@@ -274,6 +274,19 @@
         additionalProperties: false
       })
     end
+
+    it "supports reference to the root schema" do
+      schema_class.define :ui_element do
+        string :element_type, enum: ["input", "button"]
+        string :label
+        object :sub_schema, reference: :root
+      end
+
+      instance = schema_class.new
+      json_output = instance.to_json_schema
+
+      expect(json_output[:schema][:properties][:ui_schema][:properties][:sub_schema]).to eq({"$ref" => "#"})
+    end
   end
 
   # ===========================================