defaultValue: support serialization of single enum values

Also added $enumDecode[Nullable] helpers to json_annotation

Author: kevmoo

json_annotation/CHANGELOG.md

@@ -2,14 +2,18 @@
 
 * Added `JsonKey.defaultValue`.
 
+* Added helpers for deserialization of `enum` values.
+  These functions starting with `$` are  referenced by generated code.
+  They are not meant for direct use.
+
 ## 0.2.5
 
 * Added `CheckedFromJsonException` which is thrown by code generated when
  `checked` is enabled in `json_serializable`.
 
-* Added functions to support the `checked` generation option. These
-  functions start with `$` are referenced by generated code. They are not meant
-  for direct use.
+* Added functions to support the `checked` generation option.
+  These functions starting with `$` are referenced by generated code.
+  They are not meant for direct use.
 
 ## 0.2.4
 

json_annotation/lib/src/json_serializable.dart

@@ -133,3 +133,22 @@ class JsonKey {
       this.toJson,
       this.defaultValue});
 }
+
+// Until enum supports parse: github.com/dart-lang/sdk/issues/33244
+/// Helper class used in generated code with `enum` values.
+///
+/// Should not be used directly.
+T $enumDecode<T>(String enumName, List<T> values, String enumValue) =>
+    values.singleWhere((e) => e.toString() == '$enumName.$enumValue',
+        orElse: () => throw new ArgumentError(
+            '`$enumValue` is not one of the supported values: '
+            '${values.map(_nameForEnumValue).join(', ')}'));
+
+// Until enum has a name property: github.com/dart-lang/sdk/issues/21712
+String _nameForEnumValue(Object value) => value.toString().split('.')[1];
+
+/// Helper class used in generated code with nullable `enum` values.
+///
+/// Should not be used directly.
+T $enumDecodeNullable<T>(String enumName, List<T> values, String enumValue) =>
+    enumValue == null ? null : $enumDecode(enumName, values, enumValue);

json_serializable/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 * Added support for `JsonKey.defaultValue`.
 
+* `enum` deserialization now uses helpers provided by `json_annotation`.
+
 * Small change to how nullable `Map` values are deserialized.
 
 * Small whitespace changes to `JsonLiteral` generation to align with `dartfmt`.

json_serializable/lib/src/json_key_helpers.dart

@@ -11,6 +11,7 @@ import 'package:meta/meta.dart' show alwaysThrows;
 import 'package:source_gen/source_gen.dart';
 
 import 'json_literal_generator.dart';
+import 'utils.dart';
 
 @alwaysThrows
 void throwUnsupported(FieldElement element, String message) =>
@@ -45,7 +46,7 @@ JsonKeyWithConversion _from(FieldElement element) {
   var fromJsonName = _getFunctionName(obj, element, true);
   var toJsonName = _getFunctionName(obj, element, false);
 
-  Object _getLiteral(DartObject dartObject) {
+  Object _getLiteral(DartObject dartObject, Iterable<String> things) {
     if (dartObject.isNull) {
       return null;
     }
@@ -65,27 +66,51 @@ JsonKeyWithConversion _from(FieldElement element) {
     }
 
     if (badType != null) {
+      badType = things.followedBy([badType]).join(' > ');
       throwUnsupported(
           element, '`defaultValue` is `$badType`, it must be a literal.');
     }
 
     var literal = reader.literalValue;
+
     if (literal is num || literal is String || literal is bool) {
       return literal;
     } else if (literal is List<DartObject>) {
-      return literal.map(_getLiteral).toList();
-    } else if (literal is Map<DartObject, DartObject>) {
       return literal
-          .map((k, v) => new MapEntry(_getLiteral(k), _getLiteral(v)));
+          .map((e) => _getLiteral(e, things.followedBy(['List'])))
+          .toList();
+    } else if (literal is Map<DartObject, DartObject>) {
+      var mapThings = things.followedBy(['Map']);
+      return literal.map((k, v) =>
+          new MapEntry(_getLiteral(k, mapThings), _getLiteral(v, mapThings)));
     }
+
+    badType = things.followedBy(['$dartObject']).join(' > ');
+
     throwUnsupported(
-        element, 'The provided value is not supported: $dartObject');
+        element,
+        'The provided value is not supported: $badType. '
+        'This may be an error in package:json_serializable. '
+        'Please rerun your build with `--verbose` and file an issue.');
   }
 
-  var defaultValueLiteral = _getLiteral(obj.getField('defaultValue'));
-
-  if (defaultValueLiteral != null) {
-    defaultValueLiteral = jsonLiteralAsDart(defaultValueLiteral, false);
+  var defaultValueObject = obj.getField('defaultValue');
+
+  Object defaultValueLiteral;
+  if (isEnum(defaultValueObject.type)) {
+    var interfaceType = defaultValueObject.type as InterfaceType;
+    var allowedValues = interfaceType.accessors
+        .where((p) => p.returnType == interfaceType)
+        .map((p) => p.name)
+        .toList();
+    var enumValueIndex = defaultValueObject.getField('index').toIntValue();
+    defaultValueLiteral =
+        '${interfaceType.name}.${allowedValues[enumValueIndex]}';
+  } else {
+    defaultValueLiteral = _getLiteral(defaultValueObject, []);
+    if (defaultValueLiteral != null) {
+      defaultValueLiteral = jsonLiteralAsDart(defaultValueLiteral, false);
+    }
   }
 
   return new JsonKeyWithConversion._(

json_serializable/lib/src/type_helpers/enum_helper.dart

@@ -4,7 +4,6 @@
 
 import 'package:analyzer/dart/element/type.dart';
 
-import '../constants.dart' as consts;
 import '../type_helper.dart';
 import '../utils.dart';
 
@@ -31,18 +30,9 @@ class EnumHelper extends TypeHelper {
       return null;
     }
 
-    var wrappedExpression =
-        simpleExpression.hasMatch(expression) ? expression : '{$expression}';
-
-    var closureArg = consts.closureArg;
-    if (closureArg == wrappedExpression) {
-      closureArg = '${closureArg}2';
-    }
-
-    return commonNullPrefix(
-        context.nullable,
-        expression,
-        '$targetType.values.singleWhere(($closureArg) => $closureArg.toString()'
-        " == '$targetType.\$$wrappedExpression')");
+    var functionName =
+        context.nullable ? r'$enumDecodeNullable' : r'$enumDecode';
+    return "$functionName('$targetType', $targetType.values, "
+        '$expression as String)';
   }
 }

json_serializable/test/default_value/default_value.checked.dart

@@ -12,14 +12,15 @@
 
 import 'package:json_annotation/json_annotation.dart';
 
-import 'default_value_interface.dart' as dvi;
+import 'default_value_interface.dart' as dvi hide Greek;
+import 'default_value_interface.dart' show Greek;
 
 part 'default_value.checked.g.dart';
 
 const _intValue = 42;
 
 dvi.DefaultValue fromJson(Map<String, dynamic> json) =>
-    new DefaultValue.fromJson(json);
+    _$DefaultValueFromJson(json);
 
 @JsonSerializable()
 class DefaultValue extends Object
@@ -54,6 +55,9 @@ class DefaultValue extends Object
   })
   Map<String, List<String>> fieldMapListString;
 
+  @JsonKey(defaultValue: Greek.beta)
+  Greek fieldEnum;
+
   DefaultValue();
 
   factory DefaultValue.fromJson(Map<String, dynamic> json) =>

json_serializable/test/default_value/default_value.checked.g.dart

@@ -45,6 +45,12 @@ DefaultValue _$DefaultValueFromJson(Map json) =>
               {
                 'root': ['child']
               });
+      $checkedConvert(
+          json,
+          'fieldEnum',
+          (v) => val.fieldEnum =
+              $enumDecodeNullable('Greek', Greek.values, v as String) ??
+                  Greek.beta);
       return val;
     });
 
@@ -58,6 +64,7 @@ abstract class _$DefaultValueSerializerMixin {
   List<int> get fieldListSimple;
   Map<String, int> get fieldMapSimple;
   Map<String, List<String>> get fieldMapListString;
+  Greek get fieldEnum;
   Map<String, dynamic> toJson() => <String, dynamic>{
         'fieldBool': fieldBool,
         'fieldString': fieldString,
@@ -67,6 +74,8 @@ abstract class _$DefaultValueSerializerMixin {
         'fieldMapEmpty': fieldMapEmpty,
         'fieldListSimple': fieldListSimple,
         'fieldMapSimple': fieldMapSimple,
-        'fieldMapListString': fieldMapListString
+        'fieldMapListString': fieldMapListString,
+        'fieldEnum':
+            fieldEnum == null ? null : fieldEnum.toString().split('.')[1]
       };
 }

json_serializable/test/default_value/default_value.dart

@@ -6,14 +6,15 @@
 
 import 'package:json_annotation/json_annotation.dart';
 
-import 'default_value_interface.dart' as dvi;
+import 'default_value_interface.dart' as dvi hide Greek;
+import 'default_value_interface.dart' show Greek;
 
 part 'default_value.g.dart';
 
 const _intValue = 42;
 
 dvi.DefaultValue fromJson(Map<String, dynamic> json) =>
-    new DefaultValue.fromJson(json);
+    _$DefaultValueFromJson(json);
 
 @JsonSerializable()
 class DefaultValue extends Object
@@ -48,6 +49,9 @@ class DefaultValue extends Object
   })
   Map<String, List<String>> fieldMapListString;
 
+  @JsonKey(defaultValue: Greek.beta)
+  Greek fieldEnum;
+
   DefaultValue();
 
   factory DefaultValue.fromJson(Map<String, dynamic> json) =>

json_serializable/test/default_value/default_value.g.dart

@@ -30,7 +30,10 @@ DefaultValue _$DefaultValueFromJson(Map<String, dynamic> json) =>
                       k, (e as List)?.map((e) => e as String)?.toList())) ??
               {
                 'root': ['child']
-              };
+              }
+      ..fieldEnum = $enumDecodeNullable(
+              'Greek', Greek.values, json['fieldEnum'] as String) ??
+          Greek.beta;
 
 abstract class _$DefaultValueSerializerMixin {
   bool get fieldBool;
@@ -42,6 +45,7 @@ abstract class _$DefaultValueSerializerMixin {
   List<int> get fieldListSimple;
   Map<String, int> get fieldMapSimple;
   Map<String, List<String>> get fieldMapListString;
+  Greek get fieldEnum;
   Map<String, dynamic> toJson() => <String, dynamic>{
         'fieldBool': fieldBool,
         'fieldString': fieldString,
@@ -51,6 +55,8 @@ abstract class _$DefaultValueSerializerMixin {
         'fieldMapEmpty': fieldMapEmpty,
         'fieldListSimple': fieldListSimple,
         'fieldMapSimple': fieldMapSimple,
-        'fieldMapListString': fieldMapListString
+        'fieldMapListString': fieldMapListString,
+        'fieldEnum':
+            fieldEnum == null ? null : fieldEnum.toString().split('.')[1]
       };
 }

json_serializable/test/default_value/default_value_interface.dart

@@ -18,4 +18,7 @@ abstract class DefaultValue {
   List<int> fieldListSimple;
   Map<String, int> fieldMapSimple;
   Map<String, List<String>> fieldMapListString;
+  Greek fieldEnum;
 }
+
+enum Greek { alpha, beta, gamma, delta }

json_serializable/test/default_value/default_value_test.dart

@@ -21,6 +21,7 @@ const _defaultInstance = const {
   'fieldMapListString': const {
     'root': const ['child']
   },
+  'fieldEnum': 'beta'
 };
 
 const _otherValues = const {
@@ -33,8 +34,9 @@ const _otherValues = const {
   'fieldListSimple': const [4, 5, 6],
   'fieldMapSimple': const <String, dynamic>{},
   'fieldMapListString': const {
-    'root2': const ['child1', 'child2']
+    'root2': const ['alpha']
   },
+  'fieldEnum': 'delta'
 };
 
 void main() {

json_serializable/test/json_serializable_integration_test.dart

@@ -122,11 +122,12 @@ void main() {
     });
 
     test('required, but missing enum value fails', () {
-      expect(() => new Order.fromJson({}), throwsStateError);
+      expect(() => new Order.fromJson({}), throwsArgumentError);
     });
 
     test('mismatched enum value fails', () {
-      expect(() => new Order.fromJson({'category': 'weird'}), throwsStateError);
+      expect(
+          () => new Order.fromJson({'category': 'weird'}), throwsArgumentError);
     });
 
     test('platform', () {

json_serializable/test/json_serializable_test.dart

@@ -632,9 +632,9 @@ abstract class _$SubTypeSerializerMixin {
       });
       test('enum value', () {
         expectThrows(
-            'DefaultWithEnum',
+            'DefaultWithNestedEnum',
             'Error with `@JsonKey` on `field`. '
-            '`defaultValue` is `Enum`, it must be a literal.');
+            '`defaultValue` is `List > Enum`, it must be a literal.');
       });
       test('non-nullable field', () {
         expectThrows(

json_serializable/test/src/default_value_input.dart

@@ -41,11 +41,11 @@ class DefaultWithConstObject {
 enum Enum { value }
 
 @JsonSerializable()
-class DefaultWithEnum {
-  @JsonKey(defaultValue: Enum.value)
+class DefaultWithNestedEnum {
+  @JsonKey(defaultValue: [Enum.value])
   Object field;
 
-  DefaultWithEnum();
+  DefaultWithNestedEnum();
 }
 
 @JsonSerializable()

json_serializable/test/test_files/json_test_example.g.dart

@@ -13,10 +13,7 @@ part of 'json_test_example.dart';
 Person _$PersonFromJson(Map<String, dynamic> json) => new Person(
     json['firstName'] as String,
     json['lastName'] as String,
-    json[r'$house'] == null
-        ? null
-        : House.values
-            .singleWhere((e) => e.toString() == 'House.${json[r'$house']}'),
+    $enumDecodeNullable('House', House.values, json[r'$house'] as String),
     middleName: json['middleName'] as String,
     dateOfBirth: json['dateOfBirth'] == null
         ? null
@@ -25,11 +22,7 @@ Person _$PersonFromJson(Map<String, dynamic> json) => new Person(
       ? null
       : new Order.fromJson(json['order'] as Map<String, dynamic>)
   ..houseMap = (json['houseMap'] as Map<String, dynamic>)?.map((k, e) =>
-      new MapEntry(
-          k,
-          e == null
-              ? null
-              : House.values.singleWhere((e2) => e2.toString() == 'House.$e')));
+      new MapEntry(k, $enumDecodeNullable('House', House.values, e as String)));
 
 abstract class _$PersonSerializerMixin {
   String get firstName;
@@ -52,8 +45,7 @@ abstract class _$PersonSerializerMixin {
 }
 
 Order _$OrderFromJson(Map<String, dynamic> json) => new Order(
-    Category.values
-        .singleWhere((e) => e.toString() == 'Category.${json['category']}'),
+    $enumDecode('Category', Category.values, json['category'] as String),
     (json['items'] as List)?.map(
         (e) => e == null ? null : new Item.fromJson(e as Map<String, dynamic>)))
   ..count = json['count'] as int