Sbt-native-packager & AutoPlugin & Mappings in Docker

Question

This configuration works for Universal but not for Docker:

sbt-native-packager Universal config:

mappings in Universal += {
// logic like this belongs into an AutoPlugin
val confFile = buildEnv.value match {
  case BuildEnv.Development => "dev.conf"
  case BuildEnv.Test => "test.conf"
  case BuildEnv.Production => "prod.conf"
}
((resourceDirectory in Compile).value / confFile) -> "conf/application.conf"}

sbt-native-packager Docker config:

mappings in Docker += {
    // logic like this belongs into an AutoPlugin
    val confFile = buildEnv.value match {
      case BuildEnv.Development => "dev.conf"
      case BuildEnv.Test => "test.conf"
      case BuildEnv.Production => "prod.conf"
    }
    ((resourceDirectory in Compile).value / confFile) -> "conf/application.conf"}