Include type arguments when invoking fromJson on custom types. (google#984)

This fixes an edge case where the generic arguments could not be inferred.
Also DRY'd up some test helpers

Fixes google#980
Closes google#981

Author: kevmoo

json_serializable/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 5.0.2
+
+- Include type arguments when invoking `fromJson` on custom types.
+  This fixes an edge case where the generic arguments could not be inferred.
+
 ## 5.0.1
 
 - Correctly handle nullable custom objects within `Iterable` and `Map`.

json_serializable/lib/src/type_helpers/json_helper.dart

@@ -11,6 +11,7 @@ import 'package:source_gen/source_gen.dart';
 import 'package:source_helper/source_helper.dart';
 
 import '../default_container.dart';
+import '../helper_core.dart';
 import '../type_helper.dart';
 import '../utils.dart';
 import 'config_types.dart';
@@ -130,7 +131,7 @@ 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 = '${targetType.element.name}.fromJson($output)';
+    output = '${typeToCode(targetType.promoteNonNullable())}.fromJson($output)';
 
     return DefaultContainer(expression, output);
   }

json_serializable/pubspec.yaml

@@ -1,5 +1,5 @@
 name: json_serializable
-version: 5.0.1
+version: 5.0.2
 description: >-
   Automatically generate code for converting to and from JSON by annotating
   Dart classes.

json_serializable/test/generic_files/generic_argument_factories.g.dart

@@ -2,8 +2,11 @@
 // 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:collection/collection.dart';
 import 'package:json_annotation/json_annotation.dart';
 
+import '../test_utils.dart';
+
 part 'generic_class.g.dart';
 
 @JsonSerializable()
@@ -103,3 +106,40 @@ class _DurationListMillisecondConverter
   int? toJson(List<Duration>? object) =>
       object?.fold<int>(0, (sum, obj) => sum + obj.inMilliseconds);
 }
+
+class Issue980GenericClass<T> {
+  final T value;
+
+  Issue980GenericClass(this.value);
+
+  factory Issue980GenericClass.fromJson(Map<String, dynamic> json) =>
+      Issue980GenericClass(json['value'] as T);
+
+  Map<String, dynamic> toJson() => {'value': value};
+
+  @override
+  bool operator ==(Object other) =>
+      other is Issue980GenericClass && value == other.value;
+
+  @override
+  int get hashCode => value.hashCode;
+}
+
+@JsonSerializable()
+class Issue980ParentClass {
+  final List<Issue980GenericClass<int>> list;
+
+  Issue980ParentClass(this.list);
+
+  factory Issue980ParentClass.fromJson(Map<String, dynamic> json) =>
+      _$Issue980ParentClassFromJson(json);
+
+  Map<String, dynamic> toJson() => _$Issue980ParentClassToJson(this);
+
+  @override
+  bool operator ==(Object other) =>
+      other is Issue980ParentClass && deepEquals(list, other.list);
+
+  @override
+  int get hashCode => const DeepCollectionEquality().hash(list);
+}

json_serializable/test/generic_files/generic_argument_factories_nullable.g.dart

@@ -316,4 +316,14 @@ void main() {
       });
     });
   });
+
+  test('issue 980 regression test', () {
+    roundTripObject(
+      Issue980ParentClass([
+        Issue980GenericClass(45),
+        Issue980GenericClass(42),
+      ]),
+      (json) => Issue980ParentClass.fromJson(json),
+    );
+  });
 }

json_serializable/test/generic_files/generic_class.dart

@@ -4,7 +4,6 @@
 
 import 'dart:collection';
 
-import 'package:collection/collection.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 enum Category {
@@ -42,9 +41,6 @@ DateTime? dateTimeFromEpochUs(int? us) =>
 
 int? dateTimeToEpochUs(DateTime? dateTime) => dateTime?.microsecondsSinceEpoch;
 
-bool deepEquals(dynamic a, dynamic b) =>
-    const DeepCollectionEquality().equals(a, b);
-
 class Platform {
   final String description;
 

json_serializable/test/generic_files/generic_class.g.dart

@@ -7,6 +7,7 @@ import 'dart:collection';
 
 import 'package:json_annotation/json_annotation.dart';
 
+import '../test_utils.dart';
 import 'json_test_common.dart';
 
 part 'json_test_example.g.dart';