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[Suggestion] Rework Enum management #1538
Description
Take this example :
import 'package:freezed_annotation/freezed_annotation.dart';
part 'example.g.dart';
enum ExampleType { one, two, three }
@JsonSerializable()
class Example {
final ExampleType type;
final String name;
Example({
required this.type,
required this.name,
});
factory Example.fromJson(Map<String, dynamic> json) => _$ExampleFromJson(json);
Map<String, dynamic> toJson() => _$ExampleToJson(this);
}Once generated we got :
// GENERATED CODE - DO NOT MODIFY BY HAND
part of 'example.dart';
// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************
Example _$ExampleFromJson(Map<String, dynamic> json) => Example(
type: $enumDecode(_$ExampleTypeEnumMap, json['type']),
name: json['name'] as String,
);
Map<String, dynamic> _$ExampleToJson(Example instance) => <String, dynamic>{
'type': _$ExampleTypeEnumMap[instance.type]!,
'name': instance.name,
};
const _$ExampleTypeEnumMap = {
ExampleType.one: 'one',
ExampleType.two: 'two',
ExampleType.three: 'three',
};Json_serializable generates a hard-coded enum ↔ string map in the .g.dart file (e.g. _$ExampleTypeEnumMap). This duplicates information that already exists on the enum itself (Enum.values / Enum.name).
This can be error-prone, especially when the enum comes from an external package (ex: pub.dev, monorepo, ...). If that package updates the enum and build_runner is not re-run, the generated map becomes out of sync with the actual enum definition, potentially leading to errors.
Since enums already expose their values and names, it seems possible to rely on them instead of generating and maintaining a separate hard-coded map.
Activity
lucavenir commentedon Jan 7, 2026
Another thing I've noticed is that the following:
won't apply to enums, and indeed this:
Will result in generated files with a map, e.g.
I have to specify
@JsonEnum(fieldRename: .snake)explicitly to make this work. On each and every enum.DinoFive commentedon Jul 2, 2026
Consider a enum that has private enum values:
Hard-coded map doesn't work if the enum is defined in another file, since the generated file can not access
MyEnum._undefined.A custom
JsonConverteris needed to handle it:Rework enum management as @EArminjon said would make this situation simple.