[dart-dio-next][DISCUSSION] non-nullable model properties without a default value should be treated as required by default

currently when generating model types the property’s nullability is determined by 2 things

1. the property must be nullable
2. the property must be required

for example, this model:

"PaymentInfo": {
  "type": "object",
  "properties": {
    "redirectUrl": {
      "type": "string",
      "nullable": true
    },
    "invoiceId": {
      "type": "integer",
      "format": "int64"
    }
  },
  "additionalProperties": false
}

is generated as:

import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';

part 'payment_info.g.dart';

/// PaymentInfo
///
/// Properties:
/// * [redirectUrl]
/// * [invoiceId]
abstract class PaymentInfo implements Built<PaymentInfo, PaymentInfoBuilder> {
  @BuiltValueField(wireName: r'redirectUrl')
  String? get redirectUrl;

  @BuiltValueField(wireName: r'invoiceId')
  int? get invoiceId;

  PaymentInfo._();

  @BuiltValueHook(initializeBuilder: true)
  static void _defaults(PaymentInfoBuilder b) => b;

  factory PaymentInfo([void updates(PaymentInfoBuilder b)]) = _$PaymentInfo;

  @BuiltValueSerializer(custom: true)
  static Serializer<PaymentInfo> get serializer => _$PaymentInfoSerializer();
}
//stripped serializer for simplicty

as you can see, the invoiceId here is marked as nullable in the generated object, this is counter intuitive and leads to spamming ! everywhere in code

this problem is due to a limitation in built value, see:

1. https://github.com/google/built_value.dart/issues/1050
2. https://github.com/google/built_value.dart/issues/912

my suggestion is to provide an alternative factory method in addition to the built-in builder e.g.

abstract class PaymentInfo implements Built<PaymentInfo, PaymentInfoBuilder> {
  @BuiltValueField(wireName: r'redirectUrl')
  String? get redirectUrl;

  @BuiltValueField(wireName: r'invoiceId')
  int get invoiceId;

  factory PaymentInfo.strict({
    //parameters defined to reflict the matching OAS3 specification
    String? redirectUrl,
    required int invoiceId,
  }) {
    //delegate the construction to the built-in builder
    final resB = PaymentInfoBuilder();
    resB.redirectUrl = redirectUrl;
    resB.invoiceId = invoiceId;
    return resB.build();
  }

  PaymentInfo._();

  @BuiltValueHook(initializeBuilder: true)
  static void _defaults(PaymentInfoBuilder b) => b;

  factory PaymentInfo([void updates(PaymentInfoBuilder b)]) = _$PaymentInfo;

  @BuiltValueSerializer(custom: true)
  static Serializer<PaymentInfo> get serializer => _$PaymentInfoSerializer();
}

the signatures would then be handled as such:

1. non-nullable and required model property
   • non-nullable class property
   • required non-nullable factory parameter if there is no default value provided
   • non-nullable factory parameter if there is a default value provided
2. nullable and required model properties
   • nullable class property
   • required nullable factory parameter if there is no default value provided
   • nullable factory parameter if there is a default value provided
3. non-nullable and non-required model properties is this allowed ??
   • non-nullable class property
   • required non-nullable factory parameter if there is no default value provided
   • non-nullable factory parameter if there is a default value provided
4. nullable and non-required model properties
   • nullable class property
   • nullable factory parameter if there is no default value provided
   • nullable factory parameter if there is a default value provided

what are your opinions on this?

@jaumard (2018/09) @josh-burton (2019/12) @amondnet (2019/12) @sbu-WBT (2020/12) @kuhnroyal (2020/12) @agilob (2020/12)

[noordawod]

My 2 cents: “non-nullable model properties should be treated as required by default” -> should be instead: “non-nullable model properties WITHOUT A DEFAULT VALUE should be treated as required”. If it has a default value, then it shouldn’t be required unless the model says so.

[ahmednfwela]

@wing328 what do you think should be done here?