KMapperWrapper

Chooses the RETURN SHAPE of a generated mapper — @MapTo(X::class, wrapper = …) / @MapFrom(X::class, wrapper = …).

Every mapping always generates the plain core fun Source.toX(): X, which throws a MappingException on a hard failure. A wrapper adds extra extension(s) on top of it, one per wrap overload, named to{Target}{suffix} — e.g. KtResult adds fun Source.toXResult(): Result<X>. Nested mappings always call the plain core, so wrappers never affect how mappers compose.

• Default — use the module-wide setting (Gradle KMapper { wrapper = … } or the KSP option kmapper.wrapper); when nothing is configured this is None.

• None — only the plain toX().

• KtResult — also toXResult(): Result<X>.

• Flow — also toXFlow(): Flow<X>, for both a single value and a Flow of sources.

Writing your own wrapper

The built-ins use no privileged mechanism — a user wrapper is written exactly the same way: an object implementing KMapperWrapper, annotated with WrapperSuffix, with one or more public wrap functions of the shape

fun <S, T> wrap(source: <R in terms of S>, map: (S) -> T): <W in terms of T>

For each wrap overload the compiler generates fun R<Source>.to{Target}{suffix}(…externals): W<Target> = YourWrapper.wrap(this) { it.to{Target}(…externals) }.

@WrapperSuffix("Either")
object EitherWrapper : KMapperWrapper {
    fun <S, T> wrap(source: S, map: (S) -> T): Either<Throwable, T> = Either.catch { map(source) }
}

@MapTo(UserDomain::class, wrapper = EitherWrapper::class)   // → toUserDomainEither()
data class UserDto(...)

Inheritors