^ just checked Gson and it looks like they do this...

# serialization

[bissell]

^ just checked Gson and it looks like they do this as well, at least with default settings. You can freely mix 5 and "5" and into fields of int/String type and the parser will not generate an error. I dunno, seems to me like "the wrong thing" to do

[sandwwraith]

Is there any example of library that actually supports such unions?

[bissell]

There are at least a couple of approaches that work in Jackson: https://gist.github.com/abissell/a93f642c54daad3fdae4b0714c134e57

[bissell]

One method is to register alternative deserializers for String, Integer, and Long, which inspect the JSON type of the current token and refuse to deserialize a mismatched one. This works -- my implementation uses exception generation but I think it might be possible to get it to work with null instead.
The other method is to just deserialize to a Map<String, Object> and then inspect the type that Jackson picked.

[bissell]

Maybe I need to play with SerialContext a bit, I see the docs say they're similar to Jackson modules. Would still prefer to create a KSerializer that can be resolved by the plugin at compile time if possible though.