Add #[frb(json_key)] annotation to configure/control JSON keys for dart code.

[ashim-kr-saha]

Is your feature request related to a problem? Please describe.
We generated a dart structure that will have toJosn/fromJson methods. But we can't control the generated key of the JSON. eg

#[frb(dart_metadata=("freezed"))]
pub struct Tag {
    pub id: Option<String>,
    pub created_at: Option<i64>,
    pub created_by: Option<String>,
    pub updated_at: Option<i64>,
    pub updated_by: Option<String>,
    pub name: String,
}

Will generate something similar to

import 'package:flutter_rust_bridge/flutter_rust_bridge_for_generated.dart';
import 'package:freezed_annotation/freezed_annotation.dart' hide protected;

import '../frb_generated.dart';

part 'tags.freezed.dart';
part 'tags.g.dart';

@freezed
class Tag with _$Tag {
  const factory Tag({
    String? id,
    int? createdAt,
    String? createdBy,
    int? updatedAt,
    String? updatedBy,
    required String name,
  }) = _Tag;

  factory Tag.fromJson(Map<String, dynamic> json) => _$TagFromJson(json);
}

But if we need something similar to

import 'package:flutter_rust_bridge/flutter_rust_bridge_for_generated.dart';
import 'package:freezed_annotation/freezed_annotation.dart' hide protected;

import '../frb_generated.dart';

part 'tags.freezed.dart';
part 'tags.g.dart';

@freezed
class Tag with _$Tag {
  const factory Tag({
    String? id,
    @JsonKey(name: 'created_at') int? createdAt,
    @JsonKey(name: 'created_by') String? createdBy,
    @JsonKey(name: 'updated_at') int? updatedAt,
    @JsonKey(name: 'updated_by') String? updatedBy,
    required String name,
  }) = _Tag;

  factory Tag.fromJson(Map<String, dynamic> json) => _$TagFromJson(json);
}

There is no option for that.

Describe the solution you'd like
We can have a #[frb(json_key=("created_at"))] annotation to configure/control JSON keys for dart code.

#[frb(dart_metadata=("freezed"))]
pub struct Tag {
    pub id: Option<String>,

    #[frb(json_key=("created_at"))]
    pub created_at: Option<i64>,

    #[frb(json_key=("created_by"))]
    pub created_by: Option<String>,

    #[frb(json_key=("updated_at"))]
    pub updated_at: Option<i64>,

    #[frb(json_key=("updated_by"))]
    pub updated_by: Option<String>,

    pub name: String,
}

[fzyzcjy]

Looks pretty reasonable and feel free to PR for this!

Btw, in your case maybe you want a more automatic solution - https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonSerializable/fieldRename.html?

Another potential workaround: do the json serialization on the rust side using e.g. serde.

[ashim-kr-saha]

@fzyzcjy Should I try to create a PR based on #[frb(json_key=("created_at"))] approach?

[fzyzcjy]

I personally think the fieldRename approach is better for your case, because the json_key approach requires to write a lot of annotations. But feel free to choose the one you like!

[ashim-kr-saha]

I found a better option here