feature: default to creating toJson function instead of a mixin

json_serializable/CHANGELOG.md

@@ -1,5 +1,10 @@
 ## 0.6.0
 
+* **BREAKING** By default, code generated to support `toJson` now creates
+  a top-level function instead of a mixin. The default for the
+  `generate_to_json_function` is now `true`. To opt-out of this change,
+  set `generate_to_json_function` to `false`.
+
 * Now supports changing the serialized values of enums using `JsonValue`.
 
   ```dart

json_serializable/README.md

@@ -27,12 +27,13 @@ import 'package:json_annotation/json_annotation.dart';
 part 'example.g.dart';
 
 @JsonSerializable(nullable: false)
-class Person extends Object with _$PersonSerializerMixin {
+class Person {
   final String firstName;
   final String lastName;
   final DateTime dateOfBirth;
   Person({this.firstName, this.lastName, this.dateOfBirth});
   factory Person.fromJson(Map<String, dynamic> json) => _$PersonFromJson(json);
+  Map<String, dynamic> toJson() => _$PersonToJson(this);
 }
 ```
 
@@ -48,16 +49,11 @@ Person _$PersonFromJson(Map<String, dynamic> json) {
       dateOfBirth: DateTime.parse(json['dateOfBirth'] as String));
 }
 
-abstract class _$PersonSerializerMixin {
-  String get firstName;
-  String get lastName;
-  DateTime get dateOfBirth;
-  Map<String, dynamic> toJson() => <String, dynamic>{
-        'firstName': firstName,
-        'lastName': lastName,
-        'dateOfBirth': dateOfBirth.toIso8601String()
-      };
-}
+Map<String, dynamic> _$PersonToJson(Person instance) => <String, dynamic>{
+      'firstName': instance.firstName,
+      'lastName': instance.lastName,
+      'dateOfBirth': instance.dateOfBirth.toIso8601String()
+    };
 ```
 
 # Build configuration
@@ -85,14 +81,14 @@ targets:
           # Options configure how source code is generated for every
           # `@JsonSerializable`-annotated class in the package.
           #
-          # The default value for each of them: `false`.
+          # The default value for each is listed.
           #
           # For usage information, reference the corresponding field in
           # `JsonSerializableGenerator`.
-          use_wrappers: true
-          any_map: true
-          checked: true
-          explicit_to_json: true
+          use_wrappers: false
+          any_map: false
+          checked: false
+          explicit_to_json: false
           generate_to_json_function: true
 ```
 

json_serializable/example/example.dart

@@ -2,16 +2,16 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// ignore_for_file: annotate_overrides, hash_and_equals
 import 'package:json_annotation/json_annotation.dart';
 
 part 'example.g.dart';
 
 @JsonSerializable(nullable: false)
-class Person extends Object with _$PersonSerializerMixin {
+class Person {
   final String firstName;
   final String lastName;
   final DateTime dateOfBirth;
   Person({this.firstName, this.lastName, this.dateOfBirth});
   factory Person.fromJson(Map<String, dynamic> json) => _$PersonFromJson(json);
+  Map<String, dynamic> toJson() => _$PersonToJson(this);
 }

json_serializable/example/example.g.dart

@@ -17,13 +17,8 @@ Person _$PersonFromJson(Map<String, dynamic> json) {
       dateOfBirth: DateTime.parse(json['dateOfBirth'] as String));
 }
 
-abstract class _$PersonSerializerMixin {
-  String get firstName;
-  String get lastName;
-  DateTime get dateOfBirth;
-  Map<String, dynamic> toJson() => <String, dynamic>{
-        'firstName': firstName,
-        'lastName': lastName,
-        'dateOfBirth': dateOfBirth.toIso8601String()
-      };
-}
+Map<String, dynamic> _$PersonToJson(Person instance) => <String, dynamic>{
+      'firstName': instance.firstName,
+      'lastName': instance.lastName,
+      'dateOfBirth': instance.dateOfBirth.toIso8601String()
+    };

json_serializable/lib/src/json_part_builder.dart

@@ -27,7 +27,7 @@ Builder jsonPartBuilder({
   bool anyMap = false,
   bool checked = false,
   bool explicitToJson = false,
-  bool generateToJsonFunction = false,
+  bool generateToJsonFunction = true,
 }) {
   return new PartBuilder([
     new JsonSerializableGenerator(

json_serializable/lib/src/json_serializable_generator.dart

@@ -95,26 +95,26 @@ class JsonSerializableGenerator
   /// Controls how `toJson` functionality is generated for all types processed
   /// by this generator.
   ///
-  /// If `false` (the default), a private `_$ClassNameSerializerMixin` class is
-  /// created in the generated part file which contains a `toJson` method.
-  ///
-  /// Mix in this class to the source class:
+  /// If `true` (the default), then a top-level function is created that you can reference
+  /// from your class.
   ///
   /// ```dart
   /// @JsonSerializable()
-  /// class Example extends Object with _$ExampleSerializerMixin {
+  /// class Example {
   ///   // ...
+  ///   Map<String, dynamic> toJson() => _$ExampleToJson(this);
   /// }
   /// ```
   ///
-  /// If `true`, then a top-level function is created that you can reference
-  /// from your class.
+  /// If `false`, a private `_$ClassNameSerializerMixin` class is
+  /// created in the generated part file which contains a `toJson` method.
+  ///
+  /// Mix in this class to the source class:
   ///
   /// ```dart
   /// @JsonSerializable()
-  /// class Example {
+  /// class Example extends Object with _$ExampleSerializerMixin {
   ///   // ...
-  ///   Map<String, dynamic> toJson() => _$ExampleToJson(this);
   /// }
   /// ```
   final bool generateToJsonFunction;
@@ -129,12 +129,12 @@ class JsonSerializableGenerator
     bool anyMap = false,
     bool checked = false,
     bool explicitToJson = false,
-    bool generateToJsonFunction = false,
+    bool generateToJsonFunction = true,
   })  : this.useWrappers = useWrappers ?? false,
         this.anyMap = anyMap ?? false,
         this.checked = checked ?? false,
         this.explicitToJson = explicitToJson ?? false,
-        this.generateToJsonFunction = generateToJsonFunction ?? false,
+        this.generateToJsonFunction = generateToJsonFunction ?? true,
         this._typeHelpers = typeHelpers ?? _defaultHelpers;
 
   /// Creates an instance of [JsonSerializableGenerator].

json_serializable/lib/src/type_helpers/enum_helper.dart

@@ -60,8 +60,8 @@ String _enumValueMapFromType(DartType targetType) {
     return null;
   }
 
-  var items = enumMap.entries.map((e) =>
-      '  ${targetType.name}.${e.key.name}: ${jsonLiteralAsDart(e.value, false)}');
+  var items = enumMap.entries.map((e) => '  ${targetType.name}.${e.key.name}: '
+      '${jsonLiteralAsDart(e.value, false)}');
 
   return 'const ${_constMapName(targetType)} = '
       'const <${targetType.name}, dynamic>{\n${items.join(',\n')}\n};';

json_serializable/test/config_test.dart

@@ -102,7 +102,7 @@ const _validConfig = const {
   'any_map': true,
   'checked': true,
   'explicit_to_json': true,
-  'generate_to_json_function': true,
+  'generate_to_json_function': false,
 };
 
 const _invalidConfig = const {

json_serializable/test/integration/json_test_example.dart

@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// ignore_for_file: annotate_overrides, hash_and_equals
+// ignore_for_file: hash_and_equals
 import 'dart:collection';
 
 import 'package:json_annotation/json_annotation.dart';
@@ -11,7 +11,7 @@ import 'json_test_common.dart';
 part 'json_test_example.g.dart';
 
 @JsonSerializable()
-class Person extends Object with _$PersonSerializerMixin {
+class Person {
   final String firstName, middleName, lastName;
   final DateTime dateOfBirth;
   @JsonKey(name: '\$house')
@@ -26,6 +26,9 @@ class Person extends Object with _$PersonSerializerMixin {
 
   factory Person.fromJson(Map<String, dynamic> json) => _$PersonFromJson(json);
 
+  Map<String, dynamic> toJson() => _$PersonToJson(this);
+
+  @override
   bool operator ==(Object other) =>
       other is Person &&
       firstName == other.firstName &&
@@ -37,7 +40,7 @@ class Person extends Object with _$PersonSerializerMixin {
 }
 
 @JsonSerializable()
-class Order extends Object with _$OrderSerializerMixin {
+class Order {
   /// Used to test that `disallowNullValues: true` forces `includeIfNull: false`
   @JsonKey(disallowNullValue: true)
   int count;
@@ -74,6 +77,9 @@ class Order extends Object with _$OrderSerializerMixin {
 
   factory Order.fromJson(Map<String, dynamic> json) => _$OrderFromJson(json);
 
+  Map<String, dynamic> toJson() => _$OrderToJson(this);
+
+  @override
   bool operator ==(Object other) =>
       other is Order &&
       count == other.count &&
@@ -83,7 +89,7 @@ class Order extends Object with _$OrderSerializerMixin {
 }
 
 @JsonSerializable()
-class Item extends ItemCore with _$ItemSerializerMixin {
+class Item extends ItemCore {
   @JsonKey(includeIfNull: false, name: 'item-number')
   int itemNumber;
   List<DateTime> saleDates;
@@ -93,6 +99,9 @@ class Item extends ItemCore with _$ItemSerializerMixin {
 
   factory Item.fromJson(Map<String, dynamic> json) => _$ItemFromJson(json);
 
+  Map<String, dynamic> toJson() => _$ItemToJson(this);
+
+  @override
   bool operator ==(Object other) =>
       other is Item &&
       price == other.price &&
@@ -101,7 +110,7 @@ class Item extends ItemCore with _$ItemSerializerMixin {
 }
 
 @JsonSerializable()
-class Numbers extends Object with _$NumbersSerializerMixin {
+class Numbers {
   List<int> ints;
   List<num> nums;
   List<double> doubles;
@@ -120,6 +129,9 @@ class Numbers extends Object with _$NumbersSerializerMixin {
   factory Numbers.fromJson(Map<String, dynamic> json) =>
       _$NumbersFromJson(json);
 
+  Map<String, dynamic> toJson() => _$NumbersToJson(this);
+
+  @override
   bool operator ==(Object other) =>
       other is Numbers &&
       deepEquals(ints, other.ints) &&