Support using non-nullable JsonConverter on nullable properties

[rrousselGit]

This allows using JsonConverter<int, ...> on int? value.

This also gracefully handles null JSON when using JsonConverter<..., int> on Object? value, such that null is returned instead of throwing

fixes #822

[kevmoo]

Gah! Just thought of this. Create just one function. Call it $convertOrNull. There is zero benefit to have two identical functions with swapped generic arguments – right?

[rrousselGit]

Good call, I didn't realise

[rrousselGit]

Actually, I'm not sure if that's a meaningful improvement

Only one of the two functions (fromJson) is doing a cast, so their body has a difference. We always do the cast, but that'd negatively impact toJson which doesn't need one.

[kevmoo]

Please update the version to 6.3.0-dev and add a changelog entry

We can see if we can land you other change here, too!

[rrousselGit]

Done

[hasimyerlikaya]

Hi,

I have problem with this merge.
I use two converter for a custom type wich name is Ref.
I can't generate g.dart file because there is an error.

"Found more than one matching converter for Ref?."

I don't want to add annotation top of nullable field every time.
How can I use both converter with class level annotation?

Non-Nullable Converter

class RefResultConverter implements JsonConverter<Ref, dynamic> {
  const RefResultConverter();

  @override
  Ref fromJson(dynamic json) {
    if (json != null) {
      if (json["@ref"] != null) {
        final refResult = RefResult.fromJson(json["@ref"] as Map<String, dynamic>);
        return refResult.asRef();
      } else if (json["ref"] != null && json["ref"]["collection"] != null) {
        final collection = json["ref"]["collection"] as String;
        final id = json["id"] as String;
        return Ref(Collection(collection), id);
      }
    }
    return Ref.empty();
  }

  @override
  Ref toJson(Ref ref) {
    if (ref.id == null || ref.id == "") {
      return Ref.empty();
    }

    return ref;
  }
}

Nullable Converter

class RefNulableResultConverter implements JsonConverter<Ref?, dynamic> {
  const RefNulableResultConverter();

  @override
  Ref? fromJson(dynamic json) {
    if (json != null) {
      if (json["@ref"] != null) {
        final refResult = RefResult.fromJson(json["@ref"] as Map<String, dynamic>);
        return refResult.asRef();
      } else if (json["ref"] != null && json["ref"]["collection"] != null) {
        final collection = json["ref"]["collection"] as String;
        final id = json["id"] as String;
        return Ref(Collection(collection), id);
      }
    }
    return null;
  }

  @override
  Ref? toJson(Ref? ref) {
    if (ref?.id == null || ref?.id == "") {
      return null;
    }
    return ref;
  }
}

Example usage

@JsonSerializable()
@RefResultConverter()
@RefNulableResultConverter()
@AlertConverter()
class ShoppingListData {
  Ref accountRef;
  Ref privateUserRef;
  Ref walletRef;
  DateTime createdDate;

  Ref irregularExpensePlanRef;
  String name;
  bool campaignAlert;
  Alert? alert;

  @JsonKey(defaultValue: 0)
  int paymentMethodId = 0;
  Ref? personRef;
  Ref? corporationRef;
  @JsonKey(defaultValue: 1)
  int relevantTypeId = 1;
  Ref? paymentAccountRef;
  Ref? paymentCardRef;

  String? note;
  List<String>? photoUrlList;
  List<String>? audioUrlList;

  ShoppingListData({
    required this.accountRef,
    required this.privateUserRef,
    required this.walletRef,
    required this.createdDate,
    required this.irregularExpensePlanRef,
    required this.name,
    required this.campaignAlert,
    required this.paymentMethodId,
    required this.relevantTypeId,
    this.personRef,
    this.corporationRef,
    this.paymentAccountRef,
    this.paymentCardRef,
    this.alert,
    this.note,
    this.photoUrlList,
    this.audioUrlList,
  });

 

  factory ShoppingListData.fromJson(Map<String, dynamic> json) => _$ShoppingListDataFromJson(json);

  Map<String, dynamic> toJson() => _$ShoppingListDataToJson(this);
}

[rrousselGit]

You don't need to use both snnotations at the same time anymore. remove RefNulableResultConverter and your code should work

[hasimyerlikaya]

Thank you,

Actually, I tried that way, but there is a problem.

PersonRef value should be null, but Ref.empty() value.
There should be a null check during the conversion process and if json['personRef'] is null it should be set to null, no conversion should be done.

@rrousselGit

[rrousselGit]

It's just a thought but: is changing the dyanmicin your JsonConverter to Object?fixing the issue?

[hasimyerlikaya]

I don't think it will fix it, Ref.empty() value will be assigned because it will still be null.

There should be a null check and if the data is null the converter should not be called at all.

[dzluppin]

Hi,

I have problem with this merge. I use two converter for a custom type wich name is Ref. I can't generate g.dart file because there is an error.

"Found more than one matching converter for Ref?."

I have this kind of issue too.

Some of my classes have both DateTime and DateTime? attributes. And because my server returned a non-standard millisecond format, I had to create a JsonConverter class for it.

Previously, approx. 6 months ago, my code generator worked fine when running build_runner using both the nullable and non-nullable versions of JsonConverter for DateTime, but now it returns an error "Found more than one matching converter for DateTime?."