Fix: Support additionalProperties as both boolean and schema object

CHANGELOG.md

@@ -1,3 +1,16 @@
+## 2.0.0
+
+### Breaking Changes
+
+- **JSON Schema API**:
+  - `JsonObject.additionalProperties` and `JsonSchema.object(additionalProperties: ...)` now use `Object?` instead of `bool?`.
+  - `additionalProperties` may now be either `bool` or `JsonSchema`, matching the JSON Schema specification.
+
+### Reliability
+
+- **JSON Schema Parsing**:
+  - Fixed `JsonObject.fromJson` to accept untyped map values for `additionalProperties` (for example `{}` decoded as `Map<dynamic, dynamic>`), so schema objects are not silently dropped.
+
 ## 1.3.0
 
 - **Spec Alignment**:

lib/src/shared/json_schema/json_schema.dart

@@ -178,7 +178,7 @@ sealed class JsonSchema {
   static JsonObject object({
     Map<String, JsonSchema>? properties,
     List<String>? required,
-    bool? additionalProperties,
+    Object? additionalProperties,
     Map<String, List<String>>? dependentRequired,
     String? title,
     String? description,
@@ -530,7 +530,9 @@ class JsonArray extends JsonSchema {
 class JsonObject extends JsonSchema {
   final Map<String, JsonSchema>? properties;
   final List<String>? required;
-  final bool? additionalProperties;
+
+  /// Can be a [bool] (true/false) or a [JsonSchema] constraining extra properties.
+  final Object? additionalProperties;
   final Map<String, List<String>>? dependentRequired;
 
   const JsonObject({
@@ -547,6 +549,16 @@ class JsonObject extends JsonSchema {
   final Map<String, dynamic>? defaultValue;
 
   factory JsonObject.fromJson(Map<String, dynamic> json) {
+    final additionalProps = json['additionalProperties'];
+    Object? parsedAdditionalProps;
+    if (additionalProps is bool) {
+      parsedAdditionalProps = additionalProps;
+    } else if (additionalProps is Map) {
+      parsedAdditionalProps = JsonSchema.fromJson(
+        Map<String, dynamic>.from(additionalProps),
+      );
+    }
+
     return JsonObject(
       properties: (json['properties'] as Map<String, dynamic>?)?.map(
         (key, value) => MapEntry(
@@ -555,7 +567,7 @@ class JsonObject extends JsonSchema {
         ),
       ),
       required: (json['required'] as List?)?.cast<String>(),
-      additionalProperties: json['additionalProperties'] as bool?,
+      additionalProperties: parsedAdditionalProps,
       dependentRequired:
           (json['dependentRequired'] as Map<String, dynamic>?)?.map(
         (key, value) => MapEntry(
@@ -580,7 +592,9 @@ class JsonObject extends JsonSchema {
         'properties': properties!.map((k, v) => MapEntry(k, v.toJson())),
       if (required != null && required!.isNotEmpty) 'required': required,
       if (additionalProperties != null)
-        'additionalProperties': additionalProperties,
+        'additionalProperties': additionalProperties is JsonSchema
+            ? (additionalProperties as JsonSchema).toJson()
+            : additionalProperties,
       if (dependentRequired != null) 'dependentRequired': dependentRequired,
     };
   }

lib/src/shared/json_schema/json_schema_validator.dart

@@ -300,17 +300,21 @@ extension JsonSchemaValidation on JsonSchema {
     final dataKeys = data.keys.cast<String>().toSet();
     final extraKeys = dataKeys.difference(definedKeys);
 
-    // additionalProperties is a bool? in JsonObject
+    // additionalProperties can be bool or JsonSchema.
     if (schema.additionalProperties == false && extraKeys.isNotEmpty) {
       throw JsonSchemaValidationException(
         'Additional properties not allowed: ${extraKeys.join(', ')}',
         path,
       );
     }
-    // Note: JsonSchema implementation of additionalProperties as Schema is NOT in JsonObject class currently
-    // The class definition has `bool? additionalProperties`.
-    // If we wanted schema-based additionalProperties, JsonObject needs update.
-    // Proceeding with what is available.
+
+    // When additionalProperties is a JsonSchema, validate each extra key against it.
+    if (schema.additionalProperties is JsonSchema && extraKeys.isNotEmpty) {
+      final apSchema = schema.additionalProperties as JsonSchema;
+      for (final key in extraKeys) {
+        _validate(apSchema, data[key], [...path, key]);
+      }
+    }
   }
 
   void _validateEnum(JsonEnum schema, dynamic data, List<String> path) {

test/shared/json_schema_from_json_test.dart

@@ -115,6 +115,48 @@ void main() {
       });
     });
 
+    test('parses object schema with additionalProperties as schema', () {
+      final json = {
+        'type': 'object',
+        'properties': {
+          'name': {'type': 'string'},
+        },
+        'additionalProperties': {'type': 'string'},
+      };
+      final schema = JsonSchema.fromJson(json);
+      expect(schema, isA<JsonObject>());
+      final s = schema as JsonObject;
+      expect(s.additionalProperties, isA<JsonString>());
+    });
+
+    test('parses object schema with untyped additionalProperties map', () {
+      // This is what z.record(z.string(), z.unknown()) produces
+      final json = {'type': 'object', 'additionalProperties': {}};
+      final schema = JsonSchema.fromJson(json);
+      expect(schema, isA<JsonObject>());
+      final s = schema as JsonObject;
+      expect(s.additionalProperties, isA<JsonAny>());
+    });
+
+    test('parses nested object with additionalProperties as schema', () {
+      // Simulates a tool schema with a nested record/map property:
+      // e.g. z.object({ config: z.record(z.string(), z.unknown()) })
+      final json = {
+        'type': 'object',
+        'properties': {
+          'config': {
+            'type': 'object',
+            'additionalProperties': <String, dynamic>{},
+          },
+        },
+      };
+      final schema = JsonSchema.fromJson(json);
+      expect(schema, isA<JsonObject>());
+      final s = schema as JsonObject;
+      final config = s.properties!['config'] as JsonObject;
+      expect(config.additionalProperties, isA<JsonAny>());
+    });
+
     test('parses allOf schema', () {
       final json = {
         'allOf': [
@@ -192,5 +234,25 @@ void main() {
       final parsed = JsonSchema.fromJson(json);
       expect(parsed.toJson(), json);
     });
+
+    test('object with additionalProperties schema round trip', () {
+      final original = JsonSchema.object(
+        properties: {'name': JsonSchema.string()},
+        additionalProperties: JsonSchema.integer(),
+      );
+      final json = original.toJson();
+      final parsed = JsonSchema.fromJson(json);
+      expect(parsed.toJson(), json);
+    });
+
+    test('object with additionalProperties bool round trip', () {
+      final original = JsonSchema.object(
+        properties: {'name': JsonSchema.string()},
+        additionalProperties: false,
+      );
+      final json = original.toJson();
+      final parsed = JsonSchema.fromJson(json);
+      expect(parsed.toJson(), json);
+    });
   });
 }

test/shared/json_schema_test.dart

@@ -102,6 +102,22 @@ void main() {
       });
     });
 
+    test('JsonObject serializes additionalProperties as schema', () {
+      final schema = JsonSchema.object(
+        properties: {
+          'name': JsonSchema.string(),
+        },
+        additionalProperties: JsonSchema.string(),
+      );
+      expect(schema.toJson(), {
+        'type': 'object',
+        'properties': {
+          'name': {'type': 'string'},
+        },
+        'additionalProperties': {'type': 'string'},
+      });
+    });
+
     test('JsonAllOf serializes correctly', () {
       final schema = JsonSchema.allOf([
         JsonSchema.string(),

test/shared/json_schema_validator_test.dart

@@ -359,6 +359,39 @@ void main() {
           throwsA(isA<JsonSchemaValidationException>()),
         );
       });
+
+      test('validates additionalProperties as schema', () {
+        final schema = JsonSchema.object(
+          properties: {"name": JsonSchema.string()},
+          additionalProperties: JsonSchema.integer(),
+        );
+
+        // Extra property matching the schema type is valid
+        schema.validate({"name": "John", "age": 30});
+
+        // Extra property not matching the schema type throws
+        expect(
+          () => schema.validate({"name": "John", "age": "not an integer"}),
+          throwsA(isA<JsonSchemaValidationException>()),
+        );
+      });
+
+      test('validates additionalProperties as empty schema (any)', () {
+        // z.record(z.string(), z.unknown()) produces additionalProperties: {}
+        final json = {
+          'type': 'object',
+          'properties': <String, dynamic>{},
+          'additionalProperties': {},
+        };
+        final schema = JsonSchema.fromJson(json) as JsonObject;
+
+        // Any extra properties should be accepted
+        schema.validate({
+          "foo": "bar",
+          "baz": 123,
+          "nested": {"a": true},
+        });
+      });
     });
 
     group('enum validation', () {