emit "additionalProperties": false with rfl::NoExtraFields

include/rfl/json/schema/Type.hpp

@@ -101,7 +101,8 @@ struct Type {
     rfl::Flatten<Annotations> annotations{};
     rfl::Object<Type> properties{};
     std::vector<std::string> required{};
-    std::shared_ptr<Type> additionalProperties{};
+    std::optional<rfl::Variant<std::shared_ptr<Type>, bool>>
+        additionalProperties{};
   };
 
   struct OneOf {

include/rfl/parsing/NamedTupleParser.hpp

@@ -15,6 +15,7 @@
 #include "../internal/is_default_val_v.hpp"
 #include "../internal/is_extra_fields.hpp"
 #include "../internal/is_skip.hpp"
+#include "../internal/no_extra_fields_v.hpp"
 #include "../internal/nth_element_t.hpp"
 #include "../internal/ptr_cast.hpp"
 #include "../to_view.hpp"
@@ -284,6 +285,9 @@ struct NamedTupleParser {
       using U = std::remove_cvref_t<typename ExtraFieldsType::Type>;
       _schema->additional_properties_ = std::make_shared<schema::Type>(
           Parser<R, W, U, ProcessorsType>::to_schema(_definitions));
+    } else if constexpr (internal::no_extra_fields_v<ProcessorsType> &&
+                         !_no_field_names) {
+      _schema->additional_properties_ = false;
     }
   }
 

include/rfl/parsing/schema/Type.hpp

@@ -79,7 +79,7 @@ struct RFL_API Type {
 
   struct Object {
     rfl::Object<Type> types_;
-    std::shared_ptr<Type> additional_properties_;
+    rfl::Variant<std::shared_ptr<Type>, bool> additional_properties_;
   };
 
   /// All values are assumed to be required unless explicitly stated otherwise

src/rfl/json/to_schema.cpp

@@ -285,11 +285,22 @@ schema::Type type_to_json_schema_type(const parsing::schema::Type& _type,
           required.push_back(k);
         }
       }
-      auto additional_properties =
-          _t.additional_properties_
-              ? std::make_shared<schema::Type>(type_to_json_schema_type(
-                    *_t.additional_properties_, _no_required))
-              : std::shared_ptr<schema::Type>();
+      auto additional_properties = rfl::visit(
+          [&](const auto& _a)
+              -> std::optional<
+                  rfl::Variant<std::shared_ptr<schema::Type>, bool>> {
+            using A = std::remove_cvref_t<decltype(_a)>;
+            if constexpr (std::is_same<A, bool>()) {
+              return _a;
+            } else {
+              if (!_a) {
+                return std::nullopt;
+              }
+              return std::make_shared<schema::Type>(
+                  type_to_json_schema_type(*_a, _no_required));
+            }
+          },
+          _t.additional_properties_);
       return schema::Type{.value = schema::Type::Object{
                               .properties = properties,
                               .required = required,

tests/json/test_json_schema8.cpp

@@ -0,0 +1,35 @@
+#include <optional>
+#include <rfl.hpp>
+#include <rfl/json.hpp>
+#include <string>
+
+namespace test_json_schema8 {
+
+struct Address {
+  std::string street;
+  int number;
+};
+
+struct Person {
+  std::string name;
+  Address address;  // Ensures that nested objects also get
+                    // `additionalProperties: false`.
+  std::optional<int> age;
+};
+
+TEST(json, test_json_schema8) {
+  const auto json_schema = rfl::json::to_schema<Person, rfl::NoExtraFields>();
+
+  EXPECT_EQ(
+      json_schema,
+      R"({"$schema":"https://json-schema.org/draft/2020-12/schema","$ref":"#/$defs/test_json_schema8__Person","$defs":{"test_json_schema8__Address":{"type":"object","properties":{"street":{"type":"string"},"number":{"type":"integer"}},"required":["street","number"],"additionalProperties":false},"test_json_schema8__Person":{"type":"object","properties":{"name":{"type":"string"},"address":{"$ref":"#/$defs/test_json_schema8__Address"},"age":{"anyOf":[{"type":"integer"},{"type":"null"}]}},"required":["name","address"],"additionalProperties":false}}})");
+}
+
+TEST(json, test_json_schema8_without_no_extra_fields) {
+  const auto json_schema = rfl::json::to_schema<Person>();
+
+  EXPECT_EQ(
+      json_schema,
+      R"({"$schema":"https://json-schema.org/draft/2020-12/schema","$ref":"#/$defs/test_json_schema8__Person","$defs":{"test_json_schema8__Address":{"type":"object","properties":{"street":{"type":"string"},"number":{"type":"integer"}},"required":["street","number"]},"test_json_schema8__Person":{"type":"object","properties":{"name":{"type":"string"},"address":{"$ref":"#/$defs/test_json_schema8__Address"},"age":{"anyOf":[{"type":"integer"},{"type":"null"}]}},"required":["name","address"]}}})");
+}
+}  // namespace test_json_schema8