Rudder

I just tested with the following source:

object Main {

  def main(args: Array[String]): Unit = {

    println(s"Hello! Direction are: ${Direction.values.map(_.name).mkString(",")}")

  }

  sealed trait Direction { def name: String }
  object Direction {
    final case object East  extends Direction { val name = "Est" }
    final case object South extends Direction { val name = "Sud" }
    final case object West  extends Direction { val name = "Ouest" }
    final case object North extends Direction { val name = "Nord" }

    def values = ca.mrvisser.sealerate.values[Direction]
  }
}

And the runtime exec is the same, but with a BIG difference in package size:

% mvn package -q

% ls -lah target
...
-rw-r--r-- 1 fanf fanf 5.1M Nov 24 14:56 test-0.0.1-SNAPSHOT-jar-with-dependencies.jar

% java -jar target/test-0.0.1-SNAPSHOT-jar-with-dependencies.jar
Hello! Direction are: Est,Sud,Ouest,Nord

% sed -i -e "s/provided/compile/" pom.xml

% mvn clean package -q

% ls -lah target
...
-rw-r--r-- 1 fanf fanf  19M Nov 24 14:57 test-0.0.1-SNAPSHOT-jar-with-dependencies.jar

% java -jar target/test-0.0.1-SNAPSHOT-jar-with-dependencies.jar
Hello! Direction are: Est,Sud,Ouest,Nord

This is normal, as sealerate is just a compile time macro. But it hold a "compile" dependency toward scala-reflect/compiler, which accounts for ~12Mo.
We won't get the size reduction until all transitive dep toward scala-compiler are removed, but this one is a easy one to break.