Correctly handle Object?/dynamic as to/from json param type (#1307)

json_serializable/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## 6.6.2-dev
 
+- Better handling of `Object?` or `dynamic` as `fromJson` constructor param.
 - Require Dart 2.19
 
 ## 6.6.1

json_serializable/lib/src/default_container.dart

@@ -9,7 +9,7 @@ import 'utils.dart';
 /// a default value available to replace it if `null`.
 class DefaultContainer {
   final String expression;
-  final String output;
+  final Object output;
 
   DefaultContainer(this.expression, this.output);
 
@@ -23,7 +23,7 @@ class DefaultContainer {
         return ifNullOrElse(
           value.expression,
           defaultValue ?? 'null',
-          value.output,
+          value.output.toString(),
         );
       }
       value = value.output;

json_serializable/lib/src/lambda_result.dart

@@ -2,7 +2,12 @@
 // 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.
 
+import 'package:analyzer/dart/element/type.dart';
+import 'package:source_helper/source_helper.dart';
+
 import 'constants.dart' show closureArg;
+import 'shared_checkers.dart';
+import 'utils.dart';
 
 /// Represents a lambda that can be used as a tear-off depending on the context
 /// in which it is used.
@@ -13,9 +18,11 @@ import 'constants.dart' show closureArg;
 class LambdaResult {
   final String expression;
   final String lambda;
-  final String? asContent;
+  final DartType? asContent;
+
+  String get _asContent => asContent == null ? '' : _asStatement(asContent!);
 
-  String get _fullExpression => '$expression${asContent ?? ''}';
+  String get _fullExpression => '$expression$_asContent';
 
   LambdaResult(this.expression, this.lambda, {this.asContent});
 
@@ -27,3 +34,30 @@ class LambdaResult {
           ? subField.lambda
           : '($closureArg) => $subField';
 }
+
+String _asStatement(DartType type) {
+  if (type.isLikeDynamic) {
+    return '';
+  }
+
+  final nullableSuffix = type.isNullableType ? '?' : '';
+
+  if (coreIterableTypeChecker.isAssignableFromType(type)) {
+    final itemType = coreIterableGenericType(type);
+    if (itemType.isLikeDynamic) {
+      return ' as List$nullableSuffix';
+    }
+  }
+
+  if (coreMapTypeChecker.isAssignableFromType(type)) {
+    final args = type.typeArgumentsOf(coreMapTypeChecker)!;
+    assert(args.length == 2);
+
+    if (args.every((e) => e.isLikeDynamic)) {
+      return ' as Map$nullableSuffix';
+    }
+  }
+
+  final typeCode = typeToCode(type);
+  return ' as $typeCode';
+}

json_serializable/lib/src/shared_checkers.dart

@@ -6,8 +6,6 @@ import 'package:analyzer/dart/element/type.dart';
 import 'package:source_gen/source_gen.dart' show TypeChecker;
 import 'package:source_helper/source_helper.dart';
 
-import 'utils.dart';
-
 /// A [TypeChecker] for [Iterable].
 const coreIterableTypeChecker = TypeChecker.fromUrl('dart:core#Iterable');
 
@@ -27,30 +25,3 @@ const simpleJsonTypeChecker = TypeChecker.any([
   TypeChecker.fromUrl('dart:core#bool'),
   TypeChecker.fromUrl('dart:core#num')
 ]);
-
-String asStatement(DartType type) {
-  if (type.isLikeDynamic) {
-    return '';
-  }
-
-  final nullableSuffix = type.isNullableType ? '?' : '';
-
-  if (coreIterableTypeChecker.isAssignableFromType(type)) {
-    final itemType = coreIterableGenericType(type);
-    if (itemType.isLikeDynamic) {
-      return ' as List$nullableSuffix';
-    }
-  }
-
-  if (coreMapTypeChecker.isAssignableFromType(type)) {
-    final args = type.typeArgumentsOf(coreMapTypeChecker)!;
-    assert(args.length == 2);
-
-    if (args.every((e) => e.isLikeDynamic)) {
-      return ' as Map$nullableSuffix';
-    }
-  }
-
-  final typeCode = typeToCode(type);
-  return ' as $typeCode';
-}

json_serializable/lib/src/type_helpers/convert_helper.dart

@@ -6,7 +6,6 @@ import 'package:analyzer/dart/element/type.dart';
 import 'package:source_helper/source_helper.dart';
 
 import '../lambda_result.dart';
-import '../shared_checkers.dart';
 import '../type_helper.dart';
 
 /// Information used by [ConvertHelper] when handling `JsonKey`-annotated
@@ -57,7 +56,10 @@ class ConvertHelper extends TypeHelper<TypeHelperContextWithConvert> {
       return null;
     }
 
-    final asContent = asStatement(fromJsonData.paramType);
-    return LambdaResult(expression, fromJsonData.name, asContent: asContent);
+    return LambdaResult(
+      expression,
+      fromJsonData.name,
+      asContent: fromJsonData.paramType,
+    );
   }
 }

json_serializable/lib/src/type_helpers/json_converter_helper.dart

@@ -11,7 +11,6 @@ import 'package:source_gen/source_gen.dart';
 import 'package:source_helper/source_helper.dart';
 
 import '../lambda_result.dart';
-import '../shared_checkers.dart';
 import '../type_helper.dart';
 import '../utils.dart';
 
@@ -65,8 +64,6 @@ Json? $converterToJsonName<Json, Value>(
       return null;
     }
 
-    final asContent = asStatement(converter.jsonType);
-
     if (!converter.jsonType.isNullableType && targetType.isNullableType) {
       const converterFromJsonName = r'_$JsonConverterFromJson';
       context.addMember('''
@@ -88,7 +85,7 @@ Value? $converterFromJsonName<Json, Value>(
     return LambdaResult(
       expression,
       '${converter.accessString}.fromJson',
-      asContent: asContent,
+      asContent: converter.jsonType,
     );
   }
 }

json_serializable/lib/src/type_helpers/json_helper.dart

@@ -3,14 +3,14 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:collection/collection.dart';
 import 'package:json_annotation/json_annotation.dart';
 import 'package:source_gen/source_gen.dart';
 import 'package:source_helper/source_helper.dart';
 
 import '../default_container.dart';
+import '../lambda_result.dart';
 import '../type_helper.dart';
 import '../utils.dart';
 import 'config_types.dart';
@@ -130,9 +130,12 @@ class JsonHelper extends TypeHelper<TypeHelperContextWithConfig> {
 
     // TODO: the type could be imported from a library with a prefix!
     // https://github.com/google/json_serializable.dart/issues/19
-    output = '${typeToCode(targetType.promoteNonNullable())}.fromJson($output)';
+    final lambda = LambdaResult(
+      output,
+      '${typeToCode(targetType.promoteNonNullable())}.fromJson',
+    );
 
-    return DefaultContainer(expression, output);
+    return DefaultContainer(expression, lambda);
   }
 }
 
@@ -263,8 +266,7 @@ InterfaceType? _instantiate(
 
   return ctorParamType.element.instantiate(
     typeArguments: argTypes.cast<DartType>(),
-    // TODO: not 100% sure nullabilitySuffix is right... Works for now
-    nullabilitySuffix: NullabilitySuffix.none,
+    nullabilitySuffix: ctorParamType.nullabilitySuffix,
   );
 }
 

json_serializable/test/supported_types/enum_type.dart

@@ -3,3 +3,36 @@
 // BSD-style license that can be found in the LICENSE file.
 
 enum EnumType { alpha, beta, gamma, delta }
+
+class FromJsonDynamicParam {
+  FromJsonDynamicParam({required this.value});
+
+  final int value;
+
+  factory FromJsonDynamicParam.fromJson(dynamic json) =>
+      FromJsonDynamicParam(value: json as int);
+
+  dynamic toJson() => null;
+}
+
+class FromJsonNullableObjectParam {
+  FromJsonNullableObjectParam({required this.value});
+
+  final int value;
+
+  factory FromJsonNullableObjectParam.fromJson(Object? json) =>
+      FromJsonNullableObjectParam(value: json as int);
+
+  Object? toJson() => null;
+}
+
+class FromJsonObjectParam {
+  FromJsonObjectParam({required this.value});
+
+  final int value;
+
+  factory FromJsonObjectParam.fromJson(Object json) =>
+      FromJsonObjectParam(value: json as int);
+
+  dynamic toJson() => null;
+}

json_serializable/test/supported_types/input.type_iterable.dart

@@ -419,6 +419,102 @@ class SimpleClassNullableOfEnumTypeNullable {
       _$SimpleClassNullableOfEnumTypeNullableToJson(this);
 }
 
+@JsonSerializable()
+class SimpleClassOfFromJsonDynamicParam {
+  final Iterable<FromJsonDynamicParam> value;
+
+  SimpleClassOfFromJsonDynamicParam(
+    this.value,
+  );
+
+  factory SimpleClassOfFromJsonDynamicParam.fromJson(
+          Map<String, Object?> json) =>
+      _$SimpleClassOfFromJsonDynamicParamFromJson(json);
+
+  Map<String, Object?> toJson() =>
+      _$SimpleClassOfFromJsonDynamicParamToJson(this);
+}
+
+@JsonSerializable()
+class SimpleClassNullableOfFromJsonDynamicParam {
+  final Iterable<FromJsonDynamicParam>? value;
+
+  SimpleClassNullableOfFromJsonDynamicParam(
+    this.value,
+  );
+
+  factory SimpleClassNullableOfFromJsonDynamicParam.fromJson(
+          Map<String, Object?> json) =>
+      _$SimpleClassNullableOfFromJsonDynamicParamFromJson(json);
+
+  Map<String, Object?> toJson() =>
+      _$SimpleClassNullableOfFromJsonDynamicParamToJson(this);
+}
+
+@JsonSerializable()
+class SimpleClassOfFromJsonNullableObjectParam {
+  final Iterable<FromJsonNullableObjectParam> value;
+
+  SimpleClassOfFromJsonNullableObjectParam(
+    this.value,
+  );
+
+  factory SimpleClassOfFromJsonNullableObjectParam.fromJson(
+          Map<String, Object?> json) =>
+      _$SimpleClassOfFromJsonNullableObjectParamFromJson(json);
+
+  Map<String, Object?> toJson() =>
+      _$SimpleClassOfFromJsonNullableObjectParamToJson(this);
+}
+
+@JsonSerializable()
+class SimpleClassNullableOfFromJsonNullableObjectParam {
+  final Iterable<FromJsonNullableObjectParam>? value;
+
+  SimpleClassNullableOfFromJsonNullableObjectParam(
+    this.value,
+  );
+
+  factory SimpleClassNullableOfFromJsonNullableObjectParam.fromJson(
+          Map<String, Object?> json) =>
+      _$SimpleClassNullableOfFromJsonNullableObjectParamFromJson(json);
+
+  Map<String, Object?> toJson() =>
+      _$SimpleClassNullableOfFromJsonNullableObjectParamToJson(this);
+}
+
+@JsonSerializable()
+class SimpleClassOfFromJsonObjectParam {
+  final Iterable<FromJsonObjectParam> value;
+
+  SimpleClassOfFromJsonObjectParam(
+    this.value,
+  );
+
+  factory SimpleClassOfFromJsonObjectParam.fromJson(
+          Map<String, Object?> json) =>
+      _$SimpleClassOfFromJsonObjectParamFromJson(json);
+
+  Map<String, Object?> toJson() =>
+      _$SimpleClassOfFromJsonObjectParamToJson(this);
+}
+
+@JsonSerializable()
+class SimpleClassNullableOfFromJsonObjectParam {
+  final Iterable<FromJsonObjectParam>? value;
+
+  SimpleClassNullableOfFromJsonObjectParam(
+    this.value,
+  );
+
+  factory SimpleClassNullableOfFromJsonObjectParam.fromJson(
+          Map<String, Object?> json) =>
+      _$SimpleClassNullableOfFromJsonObjectParamFromJson(json);
+
+  Map<String, Object?> toJson() =>
+      _$SimpleClassNullableOfFromJsonObjectParamToJson(this);
+}
+
 @JsonSerializable()
 class SimpleClassOfInt {
   final Iterable<int> value;