[Feature Request] Add option to choose which fields should be added to toJson and fromJson

[joeldomke]

This is a more structured approach to #1178 I already started with the implementation and have written the necessary tests, but there are still some open questions, which I listed below. Once those are answered, I should be able to finish the implementation of this feature.

Problem

The current implementation does not give a lot of flexibility when it comes to defining which properties should be included in fromJson and toJson.

A property will be included in fromJson if all of the following are true:

• JsonKey.ignore == false
• JsonSerializable.createFactory == true
• The property has a setter and getter

A property will be included in toJson if one of the cases below is true:

• Case 1:
  • JsonKey.ignore == false
  • JsonSerializable.createToJson == true
  • JsonSerializable.createFactory == true
  • The property has a setter and getter
• Case 2:
  • JsonKey.ignore == false
  • JsonSerializable.createToJson == true
  • JsonSerializable.createFactory == false
  • The property has a getter

Proposal

Add JsonKey.includeWith, which is of type enum IncludeWith{none, fromJson, toJson, both}. If JsonKey.includeWith is null, we resort to the previously described behavior. Otherwise, the decisions will be made as described below. This way, we ensure backwards compatibility.

A property will be included in fromJson if all of the following are true:

• JsonKey.includeWith is one of {fromJson, both}
• JsonSerializable.createFactory == true
• The property has a setter

A property will be include in toJson if all of the following are true:

• JsonKey.includeWith is one of {toJson, both}
• JsonSerializable.createToJson == true
• The property has a getter

Open Questions

• Currently, if the field map is generated, it will include all elements that are part of fromJson and toJson. I am not sure what this field map is used for or whether it would be a breaking change, if we just included all properties that are either part of fromJson or toJson.
• What should be done if both ignore and includeWith are non null?
• What should be done if both the setter and getter have a JsonKey annotation?
• What should be done if @JsonKey(includeWith: IncludeWith.toJson) is used on a setter, that has no corresponding getter and vice versa?
• What should be done if @JsonKey(includeWith: IncludeWith.both) is used on a field that only has a setter or getter?

[kevmoo]

Duplicate of #569

Trying to align all of these requests into one place!

[kevmoo]

I have a (draft) PR out on this. I'd LOVE (early) feedback about if this works for what folks need here: #1256

I still need to do some documentation and testing...