JsonCodable should use type in Xxx.fromJson/toJson as representation in json

[a14n]

On decimal package someone reported an issue with JsonCodable. He tried the following code:

@JsonCodable()
class User {
  final Decimal? test;
  User(this.test);
}

As Decimal.fromJson accepts String as parameter he get an error because the generated code use a Map<String, Object?> as input.

It would be great if JsonCodable could read the type present in Xxx.fromJson and use it as serialization format.

[dart-github-bot]

Summary: The JsonCodable annotation currently uses Map<String, Object?> for serialization, causing issues when custom types like Decimal require specific input formats. The user suggests using the type specified in Xxx.fromJson to determine the serialization format.