It seems like mpc tool doesn't support custom resolvers.
My use-case is that I have base abstract class and would like not to use Union attributes, as there might be bunch of derived classes.
I expected to solve this by using custom formatters, while it solves issue with codegeneration, it fails in runtime if MessagePackFormatter attribute is defined on abstract class. From other hand - when there is no formatter attribute and custom resolver is registered, this fails on mpc codegeneration, but succeeds in runtime.

Is it missing feature or am I missing something here?