[BUG] ObjectMapper.readValue<T>(...) breaks null safety

[revintec]

Jackson-module-kotlin version 2.9.7, newer version should experience the same problem

changing original source code inline fun <reified T> ObjectMapper.readValue(content: String): T = readValue(content, jacksonTypeRef<T>()) adds trailing ... as T would fix the problem, however this way it provides poor exception message
Exception in thread "main" java.lang.NullPointerException: null cannot be cast to non-null type kotlin.Any

[dinomite]

Interesting, adding that cast to the extensions functions makes sense to me, but I'm a bit wary as I'm not certain what side effects it might have.

@viartemev do you have any insight?

@revintec would you make a PR with casts on the extension functions? Depending on how confident we are, this could be part of 2.12.1 or might wait until 2.13.

[revintec]

sorry for the late reply. as I discovered lately, it's more complicated than just add a as T cast

1. the exception message would not be user-friendly
2. can't cover generic class

  // should throw, instead we got a map with contaminated values
  println(JSON.readValue<Map<String,Any>>("{\"key\":null}"))

I think the right approach would be to add a isNullable alone side com.fasterxml.jackson.core.type.TypeReference._type and check null inside jackson-core when deserializing. but this requires more modification, thus I didn't come up with a PR for now