Add support for generic classes

json_serializable/CHANGELOG.md

@@ -3,13 +3,15 @@
 * Add `checked` configuration option. If `true`, generated `fromJson` functions
   include extra checks to validate proper deserialization of types.
 
-* Use `Map.map` for more map conversions. Simplifies generated code and fixes
-  a subtle issue when the `Map` key type is `dynamic` or `Object`.
-
 * Added `any_map` to configuration. Allows `fromJson` code to
   support dynamic `Map` instances that are not explicitly
   `Map<String, dynaimc>`.
 
+* Added support for classes with type arguments.
+
+* Use `Map.map` for more map conversions. Simplifies generated code and fixes
+  a subtle issue when the `Map` key type is `dynamic` or `Object`.
+
 ## 0.5.3
 
 * Require the latest version of `package:analyzer` - `v0.32.0`.

json_serializable/example/example.g.dart

@@ -1,4 +1,4 @@
-// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
 // 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.
 

json_serializable/lib/src/generator_helper.dart

@@ -39,8 +39,22 @@ class _GeneratorHelper {
   final StringBuffer _buffer = new StringBuffer();
 
   String get _prefix => '_\$${_element.name}';
-  String get _mixClassName => '${_prefix}SerializerMixin';
-  String get _helpClassName => '${_prefix}JsonMapWrapper';
+
+  String _mixinClassName(bool withConstraints) =>
+      '${_prefix}SerializerMixin${_genericClassArguments(withConstraints)}';
+
+  String _wrapperClassName([bool withConstraints]) =>
+      '${_prefix}JsonMapWrapper${_genericClassArguments(withConstraints)}';
+
+  /// Returns a [String] representing the type arguments that exist on
+  /// [_element].
+  ///
+  /// Returns the output of calling [genericClassArguments] with [_element].
+  String _genericClassArguments(bool withConstraints) =>
+      genericClassArguments(_element, withConstraints);
+
+  String get _targetClassReference =>
+      '${_element.name}${_genericClassArguments(false)}';
 
   _GeneratorHelper(this._generator, this._element, this._annotation);
 
@@ -66,7 +80,7 @@ class _GeneratorHelper {
       //
       // Generate the mixin class
       //
-      _buffer.writeln('abstract class $_mixClassName {');
+      _buffer.writeln('abstract class ${_mixinClassName(true)} {');
 
       // write copies of the fields - this allows the toJson method to access
       // the fields of the target class
@@ -80,7 +94,7 @@ class _GeneratorHelper {
       var writeNaive = accessibleFields.every(_writeJsonValueNaive);
 
       if (_generator.useWrappers) {
-        _buffer.writeln('=> new $_helpClassName(this);');
+        _buffer.writeln('=> new ${_wrapperClassName(false)}(this);');
       } else {
         if (writeNaive) {
           // write simple `toJson` method that includes all keys...
@@ -126,7 +140,8 @@ class _GeneratorHelper {
     if (_annotation.createFactory) {
       _buffer.writeln();
       var mapType = _generator.anyMap ? 'Map' : 'Map<String, dynamic>';
-      _buffer.writeln('${_element.name} ${_prefix}FromJson($mapType json) =>');
+      _buffer.writeln('$_targetClassReference '
+          '${_prefix}FromJson${_genericClassArguments(true)}($mapType json) =>');
 
       String deserializeFun(String paramOrFieldName,
               {ParameterElement ctorParam}) =>
@@ -221,9 +236,10 @@ class _GeneratorHelper {
   void _writeWrapper(Iterable<FieldElement> fields) {
     _buffer.writeln();
     // TODO(kevmoo): write JsonMapWrapper if annotation lib is prefix-imported
-    _buffer.writeln('''class $_helpClassName extends \$JsonMapWrapper {
-      final $_mixClassName _v;
-      $_helpClassName(this._v);
+    _buffer
+        .writeln('''class ${_wrapperClassName(true)} extends \$JsonMapWrapper {
+      final ${_mixinClassName(false)} _v;
+      ${_wrapperClassName()}(this._v);
     ''');
 
     if (fields.every(_writeJsonValueNaive)) {

json_serializable/lib/src/json_key_helpers.dart

@@ -108,14 +108,23 @@ ConvertData _getFunctionName(
   var argType = functionElement.parameters.first.type;
   if (isFrom) {
     var returnType = functionElement.returnType;
-    if (!returnType.isAssignableTo(element.type)) {
+
+    if (returnType is TypeParameterType) {
+      // We keep things simple in this case. We rely on inferred type arguments
+      // to the `fromJson` function.
+      // TODO: consider adding error checking here if there is confusion.
+    } else if (!returnType.isAssignableTo(element.type)) {
       _throwUnsupported(
           element,
           'The `$paramName` function `${functionElement.name}` return type '
           '`$returnType` is not compatible with field type `${element.type}`.');
     }
   } else {
-    if (!element.type.isAssignableTo(argType)) {
+    if (argType is TypeParameterType) {
+      // We keep things simple in this case. We rely on inferred type arguments
+      // to the `fromJson` function.
+      // TODO: consider adding error checking here if there is confusion.
+    } else if (!element.type.isAssignableTo(argType)) {
       _throwUnsupported(
           element,
           'The `$paramName` function `${functionElement.name}` argument type '

json_serializable/lib/src/type_helpers/convert_helper.dart

@@ -17,8 +17,8 @@ class ConvertHelper extends TypeHelper {
       DartType targetType, String expression, SerializeContext context) {
     var toJsonData = (context as TypeHelperContext).toJsonData;
     if (toJsonData != null) {
-      assert(targetType.isAssignableTo(toJsonData.paramType));
-
+      assert(toJsonData.paramType is TypeParameterType ||
+          targetType.isAssignableTo(toJsonData.paramType));
       var result = '${toJsonData.name}($expression)';
       return commonNullPrefix(context.nullable, expression, result);
     }

json_serializable/lib/src/utils.dart

@@ -175,7 +175,38 @@ int _sortByLocation(FieldElement a, FieldElement b) {
 
 final _dartCoreObjectChecker = const TypeChecker.fromRuntime(Object);
 
-/// If a parameter is required to invoke the constructor,
+/// Returns a [String] representing the type arguments that exist on
+/// [element].
+///
+/// If [withConstraints] is `null` or if [element] has no type arguments, an
+/// empty [String] is returned.
+///
+/// If [withConstraints] is true, any type constraints that exist on [element]
+/// are included.
+///
+/// For example, for class `class Sample<T as num, S>{...}`
+///
+/// For [withConstraints] = `false`:
+///
+/// ```
+/// "<T, S>"
+/// ```
+///
+/// For [withConstraints] = `true`:
+///
+/// ```
+/// "<T as num, S>"
+/// ```
+String genericClassArguments(ClassElement element, bool withConstraints) {
+  if (withConstraints == null || element.typeParameters.isEmpty) {
+    return '';
+  }
+  var values = element.typeParameters
+      .map((t) => withConstraints ? t.toString() : t.name)
+      .join(',');
+  return '<$values>';
+}
+
 /// [availableConstructorParameters] is checked to see if it is available. If
 /// [availableConstructorParameters] does not contain the parameter name,
 /// an [UnsupportedError] is thrown.
@@ -243,7 +274,7 @@ CtorData writeConstructorInvocation(
       writeableFields.toSet().difference(usedCtorParamsAndFields);
 
   var buffer = new StringBuffer();
-  buffer.write('new $className(');
+  buffer.write('new $className${genericClassArguments(classElement, false)}(');
   buffer.writeAll(
       constructorArguments.map((paramElement) =>
           deserializeForField(paramElement.name, ctorParam: paramElement)),

json_serializable/test/generic_files/generic_class.dart

@@ -0,0 +1,39 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// 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
+
+import 'package:json_annotation/json_annotation.dart';
+
+part 'generic_class.g.dart';
+
+@JsonSerializable()
+class GenericClass<T extends num, S> extends Object
+    with _$GenericClassSerializerMixin<T, S> {
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  Object fieldObject;
+
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  dynamic fieldDynamic;
+
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  int fieldInt;
+
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  T fieldT;
+
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  S fieldS;
+
+  GenericClass();
+
+  factory GenericClass.fromJson(Map<String, dynamic> json) =>
+      _$GenericClassFromJson<T, S>(json);
+}
+
+T _dataFromJson<T, S, U>(Map<String, dynamic> input, [S other1, U, other2]) =>
+    input['value'] as T;
+
+Map<String, dynamic> _dataToJson<T, S, U>(T input, [S other1, U, other2]) =>
+    {'value': input};

json_serializable/test/generic_files/generic_class.g.dart

@@ -0,0 +1,45 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// 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.
+
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'generic_class.dart';
+
+// **************************************************************************
+// Generator: JsonSerializableGenerator
+// **************************************************************************
+
+GenericClass<T, S> _$GenericClassFromJson<T extends num, S>(
+        Map<String, dynamic> json) =>
+    new GenericClass<T, S>()
+      ..fieldObject = json['fieldObject'] == null
+          ? null
+          : _dataFromJson(json['fieldObject'] as Map<String, dynamic>)
+      ..fieldDynamic = json['fieldDynamic'] == null
+          ? null
+          : _dataFromJson(json['fieldDynamic'] as Map<String, dynamic>)
+      ..fieldInt = json['fieldInt'] == null
+          ? null
+          : _dataFromJson(json['fieldInt'] as Map<String, dynamic>)
+      ..fieldT = json['fieldT'] == null
+          ? null
+          : _dataFromJson(json['fieldT'] as Map<String, dynamic>)
+      ..fieldS = json['fieldS'] == null
+          ? null
+          : _dataFromJson(json['fieldS'] as Map<String, dynamic>);
+
+abstract class _$GenericClassSerializerMixin<T extends num, S> {
+  Object get fieldObject;
+  dynamic get fieldDynamic;
+  int get fieldInt;
+  T get fieldT;
+  S get fieldS;
+  Map<String, dynamic> toJson() => <String, dynamic>{
+        'fieldObject': fieldObject == null ? null : _dataToJson(fieldObject),
+        'fieldDynamic': fieldDynamic == null ? null : _dataToJson(fieldDynamic),
+        'fieldInt': fieldInt == null ? null : _dataToJson(fieldInt),
+        'fieldT': fieldT == null ? null : _dataToJson(fieldT),
+        'fieldS': fieldS == null ? null : _dataToJson(fieldS)
+      };
+}

json_serializable/test/generic_files/generic_class.wrapped.dart

@@ -0,0 +1,45 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// 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.
+
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+// **************************************************************************
+// Generator: _WrappedGenerator
+// **************************************************************************
+
+// ignore_for_file: annotate_overrides
+
+import 'package:json_annotation/json_annotation.dart';
+
+part 'generic_class.wrapped.g.dart';
+
+@JsonSerializable()
+class GenericClass<T extends num, S> extends Object
+    with _$GenericClassSerializerMixin<T, S> {
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  Object fieldObject;
+
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  dynamic fieldDynamic;
+
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  int fieldInt;
+
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  T fieldT;
+
+  @JsonKey(fromJson: _dataFromJson, toJson: _dataToJson)
+  S fieldS;
+
+  GenericClass();
+
+  factory GenericClass.fromJson(Map<String, dynamic> json) =>
+      _$GenericClassFromJson<T, S>(json);
+}
+
+T _dataFromJson<T, S, U>(Map<String, dynamic> input, [S other1, U, other2]) =>
+    input['value'] as T;
+
+Map<String, dynamic> _dataToJson<T, S, U>(T input, [S other1, U, other2]) =>
+    {'value': input};

json_serializable/test/generic_files/generic_class.wrapped.g.dart

@@ -0,0 +1,67 @@
+// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
+// 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.
+
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'generic_class.wrapped.dart';
+
+// **************************************************************************
+// Generator: JsonSerializableGenerator
+// **************************************************************************
+
+GenericClass<T, S> _$GenericClassFromJson<T extends num, S>(
+        Map<String, dynamic> json) =>
+    new GenericClass<T, S>()
+      ..fieldObject = json['fieldObject'] == null
+          ? null
+          : _dataFromJson(json['fieldObject'] as Map<String, dynamic>)
+      ..fieldDynamic = json['fieldDynamic'] == null
+          ? null
+          : _dataFromJson(json['fieldDynamic'] as Map<String, dynamic>)
+      ..fieldInt = json['fieldInt'] == null
+          ? null
+          : _dataFromJson(json['fieldInt'] as Map<String, dynamic>)
+      ..fieldT = json['fieldT'] == null
+          ? null
+          : _dataFromJson(json['fieldT'] as Map<String, dynamic>)
+      ..fieldS = json['fieldS'] == null
+          ? null
+          : _dataFromJson(json['fieldS'] as Map<String, dynamic>);
+
+abstract class _$GenericClassSerializerMixin<T extends num, S> {
+  Object get fieldObject;
+  dynamic get fieldDynamic;
+  int get fieldInt;
+  T get fieldT;
+  S get fieldS;
+  Map<String, dynamic> toJson() => new _$GenericClassJsonMapWrapper<T, S>(this);
+}
+
+class _$GenericClassJsonMapWrapper<T extends num, S> extends $JsonMapWrapper {
+  final _$GenericClassSerializerMixin<T, S> _v;
+  _$GenericClassJsonMapWrapper(this._v);
+
+  @override
+  Iterable<String> get keys =>
+      const ['fieldObject', 'fieldDynamic', 'fieldInt', 'fieldT', 'fieldS'];
+
+  @override
+  dynamic operator [](Object key) {
+    if (key is String) {
+      switch (key) {
+        case 'fieldObject':
+          return _v.fieldObject == null ? null : _dataToJson(_v.fieldObject);
+        case 'fieldDynamic':
+          return _v.fieldDynamic == null ? null : _dataToJson(_v.fieldDynamic);
+        case 'fieldInt':
+          return _v.fieldInt == null ? null : _dataToJson(_v.fieldInt);
+        case 'fieldT':
+          return _v.fieldT == null ? null : _dataToJson(_v.fieldT);
+        case 'fieldS':
+          return _v.fieldS == null ? null : _dataToJson(_v.fieldS);
+      }
+    }
+    return null;
+  }
+}