Fix handling of nullable enum fields with includeIfNull: false (google#1227)

Fixes google#1226

Author: kevmoo

_test_yaml/test/src/build_config.g.dart

@@ -1,3 +1,7 @@
+## 6.5.3
+
+- Fixed handling of nullable `enum` fields with `includeIfNull: false`.
+
 ## 6.5.2
 
 - Better handling of `null` when encoding `enum` values or values with

json_serializable/CHANGELOG.md

@@ -7,6 +7,7 @@ import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:json_annotation/json_annotation.dart';
 import 'package:source_gen/source_gen.dart';
+import 'package:source_helper/source_helper.dart';
 
 import 'json_literal_generator.dart';
 import 'utils.dart';
@@ -16,13 +17,17 @@ String constMapName(DartType targetType) =>
 
 /// If [targetType] is not an enum, return `null`.
 ///
-/// Otherwise, returns `true` if one of the encoded values of the enum is
-/// `null`.
+/// Otherwise, returns `true` if [targetType] is nullable OR if one of the
+/// encoded values of the enum is `null`.
 bool? enumFieldWithNullInEncodeMap(DartType targetType) {
   final enumMap = _enumMap(targetType);
 
   if (enumMap == null) return null;
 
+  if (targetType.isNullableType) {
+    return true;
+  }
+
   return enumMap.values.contains(null);
 }
 

json_serializable/lib/src/enum_utils.dart

@@ -1,5 +1,5 @@
 name: json_serializable
-version: 6.5.2
+version: 6.5.3
 description: >-
   Automatically generate code for converting to and from JSON by annotating
   Dart classes.

json_serializable/pubspec.yaml

@@ -414,4 +414,9 @@ void main() {
       });
     });
   });
+
+  test('Issue1226Regression', () {
+    final instance = Issue1226Regression(durationType: null);
+    expect(instance.toJson(), isEmpty);
+  });
 }

json_serializable/test/integration/integration_test.dart

@@ -86,11 +86,21 @@ class Issue1145RegressionA {
   createFactory: false,
 )
 class Issue1145RegressionB {
-  Issue1145RegressionB({
-    required this.status,
-  });
+  Issue1145RegressionB({required this.status});
 
   Map<String, dynamic> toJson() => _$Issue1145RegressionBToJson(this);
 
   final List<Issue1145RegressionEnum?> status;
 }
+
+@JsonSerializable(includeIfNull: false)
+class Issue1226Regression {
+  Issue1226Regression({required this.durationType});
+
+  factory Issue1226Regression.fromJson(Map<String, dynamic> json) =>
+      _$Issue1226RegressionFromJson(json);
+
+  final Issue1145RegressionEnum? durationType;
+
+  Map<String, dynamic> toJson() => _$Issue1226RegressionToJson(this);
+}