Support derivation to non-sealed trait

[jtjeferreira]

Hi!

Thanks for this amazing library.

Consider the following code

import io.scalaland.chimney.Transformer
import io.scalaland.chimney.inlined._

sealed trait Foo
case object A extends Foo

sealed trait Bar
case object B extends Bar

trait Baz
case object C extends Baz


val barT = Transformer.define[Foo, Bar].withSealedSubtypeRenamed[A.type, B.type].buildTransformer //works
val bazT = Transformer.define[Foo, Baz].withSealedSubtypeRenamed[A.type, C.type].buildTransformer //fails

The definition of a Transformer from Foo to Bar works. But the definition from Foo to Baz does not because Baz is not a sealed trait.

I understand that because Baz is not sealed at compile time we can't find C, so there is not way to get Transformer.define[Foo, Baz].buildTransformer to work. But it should be possible to make Transformer.define[Foo, Baz].withSealedSubtypeRenamed[A.type, C.type].buildTransformer to work, right?

[MateuszKubuszok]

It could, but I would be worried to enable such thing without a lot of tests to make sure it would not have some unpredictable consequences:

• SealedHierarchyToSealedHierarchyRule would have to detect case when ttarget type is trait/abstract class without sealed
  • there is not cross platform utility for checking that yet, so it would have to be developed
• synthesize empty map of known types
• test what would break

[jtjeferreira]

Thanks for the reply.
I will give this a try in the next days and submit a PR with the results.

[jtjeferreira]

Hi @MateuszKubuszok, I gave this a try in #564.

SealedHierarchyToSealedHierarchyRule would have to detect case when ttarget type is trait/abstract class without sealed

I didn't implement this restriction, because I think it should be possible to configure a transformation where the target is a class (or any other type for that matter; in the example in the PR I used a String). But lets continue the discussion in the PR

[MateuszKubuszok]

Hi @jtjeferreira. Thanks! I'll review the PR later on today or tomorrow.

[jtjeferreira]

As per the comments in #564 (comment) this can be achieved without using chimney in a simpler way.