sbt sample 3

sbtSample3.scala

sealed trait Aggregation
final object Aggregation
{
	def apply(dependencies: Seq[ProjectReference], transitive: Boolean = true): Aggregation 
  = new Explicit(dependencies, transitive)
	implicit def fromBoolean(b: Boolean): Aggregation = if(b) Enabled else Disabled
	val Enabled = new Implicit(true)
	val Disabled = new Implicit(false)
	final case class Implicit(enabled: Boolean) extends Aggregation
	final class Explicit(val dependencies: Seq[ProjectReference], val transitive: Boolean)
   extends Aggregation

	final case class KeyValue[+T](key: ScopedKey[_], value: T)
	def getTasks[T](key: ScopedKey[T], structure: BuildStructure, transitive: Boolean): 
   Seq[KeyValue[T]] =
		getTasks0(key, structure, transitive, new mutable.HashMap[(ScopedKey[_], Boolean),
   Seq[KeyValue[T]]])
	private type Memo[T] = mutable.Map[(ScopedKey[_], Boolean), 
   Seq[KeyValue[T]]]
	private[this] def getTasks0[T](key: ScopedKey[T], structure: BuildStructure, 
   transitive: Boolean, memo: Memo[T]): Seq[KeyValue[T]] =
		memo.getOrElseUpdate( (key, transitive), {
			val task = structure.data.get(key.scope, key.key).toList.map(t => KeyValue(key,t))
			if(transitive) aggregateDeps(key, structure, memo) ++ task else task
		})