remove map assumption in fromJson

pkg/json/CHANGELOG.md

@@ -1,3 +1,6 @@
+# 0.20.3
+- Allow custom `fromJson` to have an arbitrary parameter type.
+
 # 0.20.2
 
 - Fix generated code syntax error when defining fields containing the dollar sign `$` by using raw strings.

pkg/json/lib/json.dart

@@ -384,16 +384,16 @@ mixin _FromJson on _Shared {
     // Otherwise, check if `classDecl` has a `fromJson` constructor.
     final constructors = await builder.constructorsOf(classDecl);
     final fromJson = constructors
-        .firstWhereOrNull((c) => c.identifier.name == 'fromJson')
-        ?.identifier;
+        .firstWhereOrNull((c) => c.identifier.name == 'fromJson');
+
     if (fromJson != null) {
       return RawCode.fromParts([
         if (nullCheck != null) nullCheck,
-        fromJson,
+        fromJson.identifier,
         '(',
         jsonReference,
         ' as ',
-        introspectionData.jsonMapCode,
+        fromJson.positionalParameters.first.type.code,
         ')',
       ]);
     }

pkg/json/pubspec.yaml

@@ -5,7 +5,7 @@ description: >
   `toJson` encoding method.
 
 repository: https://github.com/dart-lang/sdk/tree/main/pkg/json
-version: 0.20.2
+version: 0.20.3
 environment:
   sdk: ^3.6.0-edge
 dependencies:

pkg/json/test/json_codable_test.dart

@@ -25,6 +25,10 @@ void main() {
         'mapOfSerializableField': {
           'c': {'x': 3}
         },
+        'customStringSerializationField': 'hi',
+        'customMapSerializationField': {
+          'z': 'zzz',
+        }
       };
 
       var a = A.fromJson(json);
@@ -36,6 +40,9 @@ void main() {
       expect(a.listOfSerializableField.single.x, 1);
       expect(a.setOfSerializableField.single.x, 2);
       expect(a.mapOfSerializableField['c']!.x, 3);
+      expect(a.customStringSerializationField, CustomStringSerialization('hi'));
+      expect(
+          a.customMapSerializationField, CustomMapSerialization({'z': 'zzz'}));
 
       expect(a.toJson(), equals(json));
     });
@@ -56,6 +63,8 @@ void main() {
         'nullableMapOfSerializableField': {
           'd': {'x': 3},
         },
+        'nullableCustomStringSerializationField': 'hi',
+        'nullableCustomMapSerializationField': {'z': 'zzz'},
       };
 
       var b = B.fromJson(json);
@@ -67,6 +76,10 @@ void main() {
       expect(b.nullableListOfSerializableField!.single.x, 1);
       expect(b.nullableSetOfSerializableField!.single.x, 2);
       expect(b.nullableMapOfSerializableField!['d']!.x, 3);
+      expect(b.nullableCustomStringSerializationField,
+          CustomStringSerialization('hi'));
+      expect(b.nullableCustomMapSerializationField,
+          CustomMapSerialization({'z': 'zzz'}));
 
       expect(b.toJson(), equals(json));
     });
@@ -81,6 +94,8 @@ void main() {
         'nullableListOfSerializableField': null,
         'nullableSetOfSerializableField': null,
         'nullableMapOfSerializableField': null,
+        'nullableCustomStringSerializationField': null,
+        'nullableCustomMapSerializationField': null,
       });
       expect(b.nullableBoolField, null);
       expect(b.nullableStringField, null);
@@ -90,6 +105,8 @@ void main() {
       expect(b.nullableListOfSerializableField, null);
       expect(b.nullableMapOfSerializableField, null);
       expect(b.nullableSetOfSerializableField, null);
+      expect(b.nullableCustomStringSerializationField, null);
+      expect(b.nullableCustomMapSerializationField, null);
 
       expect(b.toJson(), isEmpty);
     });
@@ -104,6 +121,8 @@ void main() {
       expect(b.nullableListOfSerializableField, null);
       expect(b.nullableMapOfSerializableField, null);
       expect(b.nullableSetOfSerializableField, null);
+      expect(b.nullableCustomStringSerializationField, null);
+      expect(b.nullableCustomMapSerializationField, null);
 
       expect(b.toJson(), isEmpty);
     });
@@ -131,6 +150,11 @@ void main() {
           null,
           {'a': 1, 'b': null},
         ],
+        'listOfCustomStringSerializables': [null, 'hi'],
+        'listOfCustomMapSerializables': [
+          null,
+          {'z': 'zzz'}
+        ],
         'setOfNullableInts': [
           null,
           2,
@@ -146,6 +170,11 @@ void main() {
             'b': null,
           },
         ],
+        'setOfCustomStringSerializables': [null, 'hi'],
+        'setOfCustomMapSerializables': [
+          null,
+          {'z': 'zzz'}
+        ],
         'mapOfNullableInts': {
           'a': 3,
           'b': null,
@@ -158,6 +187,14 @@ void main() {
           'a': [null, 3],
           'b': null,
         },
+        'mapOfCustomStringSerializables': {
+          'a': null,
+          'b': 'hi',
+        },
+        'mapOfCustomMapSerializables': {
+          'a': null,
+          'b': {'z': 'zzz'},
+        },
       };
 
       var e = E.fromJson(json);
@@ -170,6 +207,13 @@ void main() {
             null,
             {'a': 1, 'b': null},
           ]));
+      expect(e.listOfCustomStringSerializables.first, null);
+      expect(e.listOfCustomStringSerializables[1],
+          CustomStringSerialization('hi'));
+      expect(e.listOfCustomMapSerializables.first, null);
+      expect(e.listOfCustomMapSerializables[1],
+          CustomMapSerialization({'z': 'zzz'}));
+
       expect(e.setOfNullableInts, equals({null, 2}));
       expect(e.setOfNullableSerializables.first!.x, 2);
       expect(e.setOfNullableSerializables.elementAt(1), null);
@@ -182,6 +226,13 @@ void main() {
               'b': null,
             },
           }));
+      expect(e.setOfCustomStringSerializables.first, null);
+      expect(e.setOfCustomStringSerializables.toList()[1],
+          CustomStringSerialization('hi'));
+      expect(e.setOfCustomMapSerializables.first, null);
+      expect(e.setOfCustomMapSerializables.toList()[1],
+          CustomMapSerialization({'z': 'zzz'}));
+
       expect(
           e.mapOfNullableInts,
           equals({
@@ -195,6 +246,12 @@ void main() {
         'a': {null, 3},
         'b': null,
       });
+      expect(e.mapOfCustomStringSerializables?['a'], null);
+      expect(e.mapOfCustomStringSerializables?['b'],
+          CustomStringSerialization('hi'));
+      expect(e.mapOfCustomMapSerializables?['a'], null);
+      expect(e.mapOfCustomMapSerializables?['b'],
+          CustomMapSerialization({'z': 'zzz'}));
 
       expect(e.toJson(), equals(json));
     });
@@ -228,6 +285,10 @@ class A {
   final Set<C> setOfSerializableField;
 
   final Map<String, C> mapOfSerializableField;
+
+  final CustomStringSerialization customStringSerializationField;
+
+  final CustomMapSerialization customMapSerializationField;
 }
 
 @JsonCodable()
@@ -247,6 +308,10 @@ class B {
   final Set<C>? nullableSetOfSerializableField;
 
   final Map<String, C>? nullableMapOfSerializableField;
+
+  final CustomStringSerialization? nullableCustomStringSerializationField;
+
+  final CustomMapSerialization? nullableCustomMapSerializationField;
 }
 
 @JsonCodable()
@@ -267,20 +332,70 @@ class E {
 
   final List<Map<String, int?>?> listOfNullableMapsOfNullableInts;
 
+  final List<CustomStringSerialization?> listOfCustomStringSerializables;
+
+  final List<CustomMapSerialization?> listOfCustomMapSerializables;
+
   final Set<int?> setOfNullableInts;
 
   final Set<C?> setOfNullableSerializables;
 
   final Set<Map<String, int?>?> setOfNullableMapsOfNullableInts;
 
+  final Set<CustomStringSerialization?> setOfCustomStringSerializables;
+
+  final Set<CustomMapSerialization?> setOfCustomMapSerializables;
+
   final Map<String, int?> mapOfNullableInts;
 
   final Map<String, C?> mapOfNullableSerializables;
 
   final Map<String, Set<int?>?> mapOfNullableSetsOfNullableInts;
+
+  final Map<String, CustomStringSerialization?> mapOfCustomStringSerializables;
+
+  final Map<String, CustomMapSerialization?> mapOfCustomMapSerializables;
 }
 
 @JsonCodable()
 class F {
   final int fieldWithDollarSign$;
 }
+
+class CustomStringSerialization {
+  final String a;
+
+  CustomStringSerialization(this.a);
+
+  String toJson() => a;
+
+  factory CustomStringSerialization.fromJson(String a) =>
+      CustomStringSerialization(a);
+
+  @override
+  bool operator ==(Object other) =>
+      other is CustomStringSerialization && a == other.a;
+
+  @override
+  int get hashCode => a.hashCode;
+}
+
+class CustomMapSerialization {
+  final Map<String, dynamic> a;
+
+  CustomMapSerialization(this.a);
+
+  Map<String, dynamic> toJson() => a;
+
+  factory CustomMapSerialization.fromJson(Map<String, dynamic> a) =>
+      CustomMapSerialization(a);
+
+  @override
+  bool operator ==(Object other) {
+    return other is CustomMapSerialization &&
+        a.toString() == other.a.toString();
+  }
+
+  @override
+  int get hashCode => a.hashCode;
+}