allow setting initialization to be partially dynamic and run in parallel

main/Defaults.scala

@@ -212,9 +212,7 @@ object Defaults extends BuildCommon
 		} join
 	}
 	def watchTransitiveSourcesTask: Initialize[Task[Seq[File]]] =
-		(state, thisProjectRef) flatMap { (s, base) =>
-			inAllDependencies(base, watchSources.task, Project structure s).join.map(_.flatten)
-		}
+		inDependencies[Task[Seq[File]]](watchSources.task, const(std.TaskExtra.constant(Nil)), includeRoot = true) apply { _.join.map(_.flatten) }
 	def watchSourcesTask: Initialize[Task[Seq[File]]] =
 		Seq(unmanagedSources, unmanagedResources).map(inAllConfigurations).join { _.join.map(_.flatten.flatten.distinct) }
 
@@ -512,19 +510,21 @@ object Defaults extends BuildCommon
 		recurse ?? Nil
 	}
 
-	def inAllDependencies[T](base: ProjectRef, key: ScopedSetting[T], structure: Load.BuildStructure): Seq[T] =
-	{
-		def deps(ref: ProjectRef): Seq[ProjectRef] =
-			Project.getProject(ref, structure).toList.flatMap { p =>
-				p.dependencies.map(_.project) ++ p.aggregate
-			}
+	def inDependencies[T](key: ScopedSetting[T], default: ProjectRef => T, includeRoot: Boolean = true, classpath: Boolean = true, aggregate: Boolean = false): Initialize[Seq[T]] =
+		Project.bind( (loadedBuild, thisProjectRef).identity ) { case (lb, base) =>
+			transitiveDependencies(base, lb, includeRoot, classpath, aggregate) map ( ref => (key in ref) ?? default(ref) ) join ;
+		}
 
-		inAllDeps(base, deps, key, structure.data)
+	def transitiveDependencies(base: ProjectRef, structure: Load.LoadedBuild, includeRoot: Boolean, classpath: Boolean = true, aggregate: Boolean = false): Seq[ProjectRef] =
+	{
+		val full = Dag.topologicalSort(base)(getDependencies(structure, classpath, aggregate))
+		if(includeRoot) full else full.dropRight(1)
 	}
-	def inAllDeps[T](base: ProjectRef, deps: ProjectRef => Seq[ProjectRef], key: ScopedSetting[T], data: Settings[Scope]): Seq[T] =
-		inAllProjects(Dag.topologicalSort(base)(deps), key, data)
-	def inAllProjects[T](allProjects: Seq[Reference], key: ScopedSetting[T], data: Settings[Scope]): Seq[T] =
-		allProjects.flatMap { p => key in p get data }
+	def getDependencies(structure: Load.LoadedBuild, classpath: Boolean = true, aggregate: Boolean = false): ProjectRef => Seq[ProjectRef] =
+		ref => Project.getProject(ref, structure).toList flatMap { p =>
+			(if(classpath) p.dependencies.map(_.project) else Nil) ++
+			(if(aggregate) p.aggregate else Nil)
+		}
 
 	val CompletionsID = "completions"
 	

main/Project.scala

@@ -149,8 +149,10 @@ object Project extends Init[Scope] with ProjectExtra
 
 	def getProjectForReference(ref: Reference, structure: BuildStructure): Option[ResolvedProject] =
 		ref match { case pr: ProjectRef => getProject(pr, structure); case _ => None }
-	def getProject(ref: ProjectRef, structure: BuildStructure): Option[ResolvedProject] =
-		(structure.units get ref.build).flatMap(_.defined get ref.project)
+	def getProject(ref: ProjectRef, structure: BuildStructure): Option[ResolvedProject] = getProject(ref, structure.units)
+	def getProject(ref: ProjectRef, structure: Load.LoadedBuild): Option[ResolvedProject] = getProject(ref, structure.units)
+	def getProject(ref: ProjectRef, units: Map[URI, Load.LoadedBuildUnit]): Option[ResolvedProject] =
+		(units get ref.build).flatMap(_.defined get ref.project)
 
 	def setProject(session: SessionSettings, structure: BuildStructure, s: State): State =
 	{

sbt/src/sbt-test/project/settings-compat/build.sbt

@@ -0,0 +1,14 @@
+// check that a plain File can be appended to Classpath
+unmanagedJars in Compile += file("doesnotexist")
+
+unmanagedJars in Compile ++= Seq( file("doesnotexist1"), file("doesnotexist2") )
+
+// check that an Attributed File can be appended to Classpath
+unmanagedJars in Compile += Attributed.blank(file("doesnotexist"))
+
+unmanagedJars in Compile ++= Attributed.blankSeq( Seq( file("doesnotexist1"), file("doesnotexist2") ) )
+
+maxErrors += 1
+
+name += "-demo"
+

sbt/src/sbt-test/project/settings-compat/test

@@ -0,0 +1,2 @@
+# this test contains source compatibility checks for settings
+> test

tasks/src/test/scala/TaskRunnerCircular.scala

@@ -26,16 +26,12 @@ object TaskRunnerCircularTest extends Properties("TaskRunner Circular")
 	{
 		lazy val top = iterate(pure("bottom", intermediate), intermediate)
 		def iterate(task: Task[Int], i: Int): Task[Int] =
-		{
-			lazy val it: Task[Int] =
-				task flatMap { t =>
-					if(t <= 0)
-						top
-					else
-						iterate(pure((t-1).toString, t-1), i-1)
-				}
-			it
-		}
+			task flatMap { t =>
+				if(t <= 0)
+					top
+				else
+					iterate(pure((t-1).toString, t-1), i-1)
+			}
 		try { tryRun(top, true, workers); false }
 		catch { case i: Incomplete => cyclic(i) }
 	}

util/collection/INode.scala

@@ -0,0 +1,172 @@
+package sbt
+
+	import java.lang.Runnable
+	import java.util.concurrent.{atomic, Executor, LinkedBlockingQueue}
+	import atomic.{AtomicBoolean, AtomicInteger}
+	import Types.{:+:, Id}
+
+object EvaluationState extends Enumeration {
+	val New, Blocked, Ready, Calling, Evaluated = Value
+}
+
+abstract class EvaluateSettings[Scope]
+{
+	protected val init: Init[Scope]
+	import init._
+	protected def executor: Executor
+	protected def compiledSettings: Seq[Compiled[_]]
+
+		import EvaluationState.{Value => EvaluationState, _}
+
+	private[this] val complete = new LinkedBlockingQueue[Option[Throwable]]
+	private[this] val static = PMap.empty[ScopedKey, INode]
+	private[this] def getStatic[T](key: ScopedKey[T]): INode[T] = static get key getOrElse error("Illegal reference to key " + key)
+
+	private[this] val transform: Initialize ~> INode = new (Initialize ~> INode) { def apply[T](i: Initialize[T]): INode[T] = i match {
+		case k: Keyed[s, T] => single(getStatic(k.scopedKey), k.transform)
+		case a: Apply[hl,T] => new MixedNode(a.inputs transform transform, a.f)
+		case u: Uniform[s, T] => new UniformNode(u.inputs map transform.fn[s], u.f)
+		case b: Bind[s,T] => new BindNode[s,T]( transform(b.in), x => transform(b.f(x)))
+		case v: Value[T] => constant(v.value)
+		case o: Optional[s,T] => o.a match {
+			case None => constant( () => o.f(None) )
+			case Some(i) => single[s,T](transform(i), x => o.f(Some(x)))
+		}
+	}}
+	private[this] val roots: Seq[INode[_]] = compiledSettings flatMap { cs =>
+		(cs.settings map { s =>
+			val t = transform(s.init)
+			static(s.key) = t
+			t
+		}): Seq[INode[_]]
+	}
+	private[this] var running = new AtomicInteger
+	private[this] var cancel = new AtomicBoolean(false)
+
+	def run(implicit delegates: Scope => Seq[Scope]): Settings[Scope] =
+	{
+		assert(running.get() == 0, "Already running")
+		startWork()
+		roots.foreach( _.registerIfNew() )
+		workComplete()
+		complete.take() foreach { ex =>
+			cancel.set(true)
+			throw ex
+		}
+		getResults(delegates)
+	}
+	private[this] def getResults(implicit delegates: Scope => Seq[Scope]) = (empty /: static.toTypedSeq) { case (ss, static.TPair(key, node)) => ss.set(key.scope, key.key, node.get) }
+	private[this] val getValue = new (INode ~> Id) { def apply[T](node: INode[T]) = node.get }
+
+	private[this] def submitEvaluate(node: INode[_]) = submit(node.evaluate())
+	private[this] def submitCallComplete[T](node: BindNode[_, T], value: T) = submit(node.callComplete(value))
+	private[this] def submit(work: => Unit): Unit =
+	{
+		startWork()
+		executor.execute(new Runnable { def run = if(!cancel.get()) run0(work) })
+	}
+	private[this] def run0(work: => Unit): Unit =
+	{
+		try { work } catch { case e => complete.put( Some(e) ) }
+		workComplete()
+	}
+
+	private[this] def startWork(): Unit = running.incrementAndGet()
+	private[this] def workComplete(): Unit =
+		if(running.decrementAndGet() == 0)
+			complete.put( None )
+	
+	private[this] sealed abstract class INode[T]
+	{
+		private[this] var state: EvaluationState = New
+		private[this] var value: T = _
+		private[this] val blocking = new collection.mutable.ListBuffer[INode[_]]
+		private[this] var blockedOn: Int = 0
+		private[this] val calledBy = new collection.mutable.ListBuffer[BindNode[_, T]]
+
+		override def toString = getClass.getName + " (state=" + state + ",blockedOn=" + blockedOn + ",calledBy=" + calledBy.size + ",blocking=" + blocking.size + "): " +
+			( (static.toSeq.flatMap { case (key, value) => if(value eq this) key.toString :: Nil else Nil }).headOption getOrElse "non-static")
+	
+		final def get: T = synchronized {
+			assert(value != null, toString + " not evaluated")
+			value
+		}
+		final def doneOrBlock(from: INode[_]): Boolean = synchronized {
+			val ready = state == Evaluated
+			if(!ready) blocking += from
+			registerIfNew()
+			ready	
+		}
+		final def isDone: Boolean = synchronized { state == Evaluated }
+		final def isNew: Boolean = synchronized { state == New }
+		final def isCalling: Boolean = synchronized { state == Calling }
+		final def registerIfNew(): Unit = synchronized { if(state == New) register() }
+		private[this] def register()
+		{
+			assert(state == New, "Already registered and: " + toString)
+			val deps = dependsOn
+			blockedOn = deps.size - deps.count(_.doneOrBlock(this))
+			if(blockedOn == 0)
+				schedule()
+			else
+				state = Blocked
+		}
+	
+		final def schedule(): Unit = synchronized {
+			assert(state == New || state == Blocked, "Invalid state for schedule() call: " + toString)
+			state = Ready
+			submitEvaluate(this)
+		}
+		final def unblocked(): Unit = synchronized {
+			assert(state == Blocked, "Invalid state for unblocked() call: " + toString)
+			blockedOn -= 1
+			assert(blockedOn >= 0, "Negative blockedOn: " + blockedOn + " for " + toString)
+			if(blockedOn == 0) schedule()
+		}
+		final def evaluate(): Unit = synchronized { evaluate0() }
+		protected final def makeCall(source: BindNode[_, T], target: INode[T]) {
+			assert(state == Ready, "Invalid state for call to makeCall: " + toString)
+			state = Calling
+			target.call(source)
+		}
+		protected final def setValue(v: T) {
+			assert(state != Evaluated, "Already evaluated (trying to set value to " + v + "): " + toString)
+			value = v
+			state = Evaluated
+			blocking foreach { _.unblocked() }
+			blocking.clear()
+			calledBy foreach { node => submitCallComplete(node, value) }
+			calledBy.clear()
+		}
+		final def call(by: BindNode[_, T]): Unit = synchronized {
+			registerIfNew()
+			state match {
+				case Evaluated => submitCallComplete(by, value)
+				case _ => calledBy += by
+			}
+		}
+		protected def dependsOn: Seq[INode[_]]
+		protected def evaluate0(): Unit
+	}
+	private[this] def constant[T](f: () => T): INode[T] = new MixedNode[HNil, T](KNil, _ => f())
+	private[this] def single[S,T](in: INode[S], f: S => T): INode[T] = new MixedNode[S :+: HNil, T](in :^: KNil, hl => f(hl.head))
+	private[this] final class BindNode[S,T](in: INode[S], f: S => INode[T]) extends INode[T]
+	{
+		protected def dependsOn = in :: Nil
+		protected def evaluate0(): Unit = makeCall(this, f(in.get) )
+		def callComplete(value: T): Unit = synchronized {
+			assert(isCalling, "Invalid state for callComplete(" + value + "): " + toString)
+			setValue(value)
+		}
+	}
+	private[this] final class UniformNode[S,T](in: Seq[INode[S]], f: Seq[S] => T) extends INode[T]
+	{
+		protected def dependsOn = in
+		protected def evaluate0(): Unit = setValue( f(in.map(_.get)) )
+	}
+	private[this] final class MixedNode[HL <: HList, T](in: KList[INode, HL], f: HL => T) extends INode[T]
+	{
+		protected def dependsOn = in.toList
+		protected def evaluate0(): Unit = setValue( f( in down getValue ) )
+	}
+}

util/collection/PMap.scala

@@ -12,9 +12,12 @@ trait RMap[K[_], V[_]]
 	def get[T](k: K[T]): Option[V[T]]
 	def contains[T](k: K[T]): Boolean
 	def toSeq: Seq[(K[_], V[_])]
+	def toTypedSeq = toSeq.map{ case (k: K[t],v) => TPair[t](k,v.asInstanceOf[V[t]]) }
 	def keys: Iterable[K[_]]
 	def values: Iterable[V[_]]
 	def isEmpty: Boolean
+
+	final case class TPair[T](key: K[T], value: V[T])
 }
 
 trait IMap[K[_], V[_]] extends (K ~> V) with RMap[K,V]

util/collection/Settings.scala

@@ -50,7 +50,7 @@ trait Init[Scope]
 
 	type SettingSeq[T] = Seq[Setting[T]]
 	type ScopedMap = IMap[ScopedKey, SettingSeq]
-	type CompiledMap = Map[ScopedKey[_], Compiled]
+	type CompiledMap = Map[ScopedKey[_], Compiled[_]]
 	type MapScoped = ScopedKey ~> ScopedKey
 	type ValidatedRef[T] = Either[Undefined, ScopedKey[T]]
 	type ValidatedInit[T] = Either[Seq[Undefined], Initialize[T]]
@@ -62,6 +62,7 @@ trait Init[Scope]
 	def value[T](value: => T): Initialize[T] = new Value(value _)
 	def optional[T,U](i: Initialize[T])(f: Option[T] => U): Initialize[U] = new Optional(Some(i), f)
 	def update[T](key: ScopedKey[T])(f: T => T): Setting[T] = new Setting[T](key, app(key :^: KNil)(hl => f(hl.head)))
+	def bind[S,T](in: Initialize[S])(f: S => Initialize[T]): Initialize[T] = new Bind(f, in)
 	def app[HL <: HList, T](inputs: KList[Initialize, HL])(f: HL => T): Initialize[T] = new Apply(f, inputs)
 	def uniform[S,T](inputs: Seq[Initialize[S]])(f: Seq[S] => T): Initialize[T] = new Uniform(f, inputs)
 
@@ -87,18 +88,18 @@ trait Init[Scope]
 	{
 		val cMap = compiled(init)(delegates, scopeLocal, display)
 		// order the initializations.  cyclic references are detected here.
-		val ordered: Seq[Compiled] = sort(cMap)
+		val ordered: Seq[Compiled[_]] = sort(cMap)
 		// evaluation: apply the initializations.
-		applyInits(ordered)
+		try { applyInits(ordered) }
+		catch { case rru: RuntimeUndefined => throw Uninitialized(cMap.keys.toSeq, delegates, rru.undefined, true) }
 	}
-	def sort(cMap: CompiledMap): Seq[Compiled] =
+	def sort(cMap: CompiledMap): Seq[Compiled[_]] =
 		Dag.topologicalSort(cMap.values)(_.dependencies.map(cMap))
 
 	def compile(sMap: ScopedMap): CompiledMap =
-		sMap.toSeq.map { case (k, ss) =>
+		sMap.toTypedSeq.map { case sMap.TPair(k, ss) =>
 			val deps = ss flatMap { _.dependsOn } toSet;
-			val eval = (settings: Settings[Scope]) => (settings /: ss)(applySetting)
-			(k, new Compiled(k, deps, eval))
+			(k, new Compiled(k, deps, ss))
 		} toMap;
 
 	def grouped(init: Seq[Setting[_]]): ScopedMap =
@@ -144,14 +145,17 @@ trait Init[Scope]
 		resolve(scopes)
 	}
 		
-	private[this] def applyInits(ordered: Seq[Compiled])(implicit delegates: Scope => Seq[Scope]): Settings[Scope] =
-		(empty /: ordered){ (m, comp) => comp.eval(m) }
-
-	private[this] def applySetting[T](map: Settings[Scope], setting: Setting[T]): Settings[Scope] =
+	private[this] def applyInits(ordered: Seq[Compiled[_]])(implicit delegates: Scope => Seq[Scope]): Settings[Scope] =
 	{
-		val value = setting.init.evaluate(map)
-		val key = setting.key
-		map.set(key.scope, key.key, value)
+		val x = java.util.concurrent.Executors.newFixedThreadPool(Runtime.getRuntime.availableProcessors)
+		try {
+			val eval: EvaluateSettings[Scope] = new EvaluateSettings[Scope] {
+				override val init: Init.this.type = Init.this
+				def compiledSettings = ordered
+				def executor = x
+			}
+			eval.run
+		} finally { x.shutdown() }
 	}
 
 	def showUndefined(u: Undefined, validKeys: Seq[ScopedKey[_]], delegates: Scope => Seq[Scope])(implicit display: Show[ScopedKey[_]]): String =
@@ -185,7 +189,7 @@ trait Init[Scope]
 		val keysString = keys.map(u => showUndefined(u, validKeys, delegates)).mkString("\n\n  ", "\n\n  ", "")
 		new Uninitialized(keys, prefix + suffix + " to undefined setting" + suffix + ": " + keysString + "\n ")
 	}
-	final class Compiled(val key: ScopedKey[_], val dependencies: Iterable[ScopedKey[_]], val eval: Settings[Scope] => Settings[Scope])
+	final class Compiled[T](val key: ScopedKey[T], val dependencies: Iterable[ScopedKey[_]], val settings: Seq[Setting[T]])
 	{
 		override def toString = showFullKey(key)
 	}
@@ -253,7 +257,7 @@ trait Init[Scope]
 	sealed trait Keyed[S, T] extends Initialize[T]
 	{
 		def scopedKey: ScopedKey[S]
-		protected def transform: S => T
+		def transform: S => T
 		final def dependsOn = scopedKey :: Nil
 		final def apply[Z](g: T => Z): Initialize[Z] = new GetValue(scopedKey, g compose transform)
 		final def evaluate(ss: Settings[Scope]): T = transform(getValue(ss, scopedKey))
@@ -271,10 +275,24 @@ trait Init[Scope]
 	}
 	private[this] final class GetValue[S,T](val scopedKey: ScopedKey[S], val transform: S => T) extends Keyed[S, T]
 	trait KeyedInitialize[T] extends Keyed[T, T] {
-		protected final val transform = idFun[T]
+		final val transform = idFun[T]
 	}
-	
-	private[this] final class Optional[S,T](a: Option[Initialize[S]], f: Option[S] => T) extends Initialize[T]
+	private[sbt] final class Bind[S,T](val f: S => Initialize[T], val in: Initialize[S]) extends Initialize[T]
+	{
+		def dependsOn = in.dependsOn
+		def apply[Z](g: T => Z): Initialize[Z] = new Bind[S,Z](s => f(s)(g), in)
+		def evaluate(ss: Settings[Scope]): T = f(in evaluate ss) evaluate ss
+		def mapReferenced(g: MapScoped) = new Bind[S,T](s => f(s) mapReferenced g, in mapReferenced g)
+		def validateReferenced(g: ValidateRef) = (in validateReferenced g).right.map { validIn =>
+			new Bind[S,T](s => handleUndefined( f(s) validateReferenced g), validIn)
+		}
+		def handleUndefined(vr: ValidatedInit[T]): Initialize[T] = vr match {
+			case Left(undefs) => throw new RuntimeUndefined(undefs)
+			case Right(x) => x
+		}
+		def mapConstant(g: MapConstant) = new Bind[S,T](s => f(s) mapConstant g, in mapConstant g)
+	}
+	private[sbt] final class Optional[S,T](val a: Option[Initialize[S]], val f: Option[S] => T) extends Initialize[T]
 	{
 		def dependsOn = dependencies(a.toList)
 		def apply[Z](g: T => Z): Initialize[Z] = new Optional[S,Z](a, g compose f)
@@ -283,7 +301,7 @@ trait Init[Scope]
 		def validateReferenced(g: ValidateRef) = Right( new Optional(a flatMap { _.validateReferenced(g).right.toOption }, f) )
 		def mapConstant(g: MapConstant): Initialize[T] = new Optional(a map mapConstantT(g).fn, f)
 	}
-	private[this] final class Value[T](value: () => T) extends Initialize[T]
+	private[sbt] final class Value[T](val value: () => T) extends Initialize[T]
 	{
 		def dependsOn = Nil
 		def mapReferenced(g: MapScoped) = this
@@ -292,7 +310,7 @@ trait Init[Scope]
 		def mapConstant(g: MapConstant) = this
 		def evaluate(map: Settings[Scope]): T = value()
 	}
-	private[this] final class Apply[HL <: HList, T](val f: HL => T, val inputs: KList[Initialize, HL]) extends Initialize[T]
+	private[sbt] final class Apply[HL <: HList, T](val f: HL => T, val inputs: KList[Initialize, HL]) extends Initialize[T]
 	{
 		def dependsOn = dependencies(inputs.toList)
 		def mapReferenced(g: MapScoped) = mapInputs( mapReferencedT(g) )
@@ -308,7 +326,7 @@ trait Init[Scope]
 			if(undefs.isEmpty) Right(new Apply(f, tx transform get)) else Left(undefs)
 		}
 	}
-	private[this] final class Uniform[S, T](val f: Seq[S] => T, val inputs: Seq[Initialize[S]]) extends Initialize[T]
+	private[sbt] final class Uniform[S, T](val f: Seq[S] => T, val inputs: Seq[Initialize[S]]) extends Initialize[T]
 	{
 		def dependsOn = dependencies(inputs)
 		def mapReferenced(g: MapScoped) = new Uniform(f, inputs map mapReferencedT(g).fn)

util/collection/src/test/scala/SettingsExample.scala

@@ -59,9 +59,9 @@ object SettingsUsage
 	val applied: Settings[Scope] = make(mySettings)(delegates, scopeLocal, showFullKey)
 
 		// Show results.
-	for(i <- 0 to 5; k <- Seq(a, b)) {
+/*	for(i <- 0 to 5; k <- Seq(a, b)) {
 		println( k.label + i + " = " + applied.get( Scope(i), k) )
-	}
+	}*/
 
 /** Output:
 * For the None results, we never defined the value and there was no value to delegate to.

util/collection/src/test/scala/SettingsTest.scala

@@ -3,21 +3,96 @@ package sbt
 import org.scalacheck._
 import Prop._
 import SettingsUsage._
+import SettingsExample._
 
 object SettingsTest extends Properties("settings")
 {
-	def tests = 
-		for(i <- 0 to 5; k <- Seq(a, b)) yield {
-			val value = applied.get( Scope(i), k)
-			val expected = expectedValues(2*i + (if(k == a) 0 else 1))
-			("Index: " + i) |:
-			("Key: " + k.label) |:
-			("Value: " + value) |:
-			("Expected: " + expected) |:
-			(value == expected)
-		}
+	final val ChainMax = 5000
+	lazy val chainLengthGen = Gen.choose(1, ChainMax)
 
 	property("Basic settings test") = secure( all( tests: _*) )
 
+	property("Basic chain") = forAll(chainLengthGen) { (i: Int) => 
+		val abs = math.abs(i)
+		singleIntTest( chain( abs, value(0)), abs )
+	}
+	property("Basic bind chain") = forAll(chainLengthGen) { (i: Int) =>
+		val abs = math.abs(i)
+		singleIntTest( chainBind(value(abs)), 0 )
+	}
+
+	property("Allows references to completed settings") = forAllNoShrink(30) { allowedReference _ }
+	final def allowedReference(intermediate: Int): Prop =
+	{
+		val top = value(intermediate)
+		def iterate(init: Initialize[Int]): Initialize[Int] =
+			bind(init) { t =>
+				if(t <= 0)
+					top
+				else
+					iterate(value(t-1) )
+			}
+		try { evaluate( setting(chk, iterate(top)) :: Nil); true }
+		catch { case e: Exception => ("Unexpected exception: " + e) |: false }
+	}
+
+// Circular (dynamic) references currently loop infinitely.
+//  This is the expected behavior (detecting dynamic cycles is expensive),
+//  but it may be necessary to provide an option to detect them (with a performance hit)
+// This would test that cycle detection.
+//	property("Catches circular references") = forAll(chainLengthGen) { checkCircularReferences _ }
+	final def checkCircularReferences(intermediate: Int): Prop =
+	{
+		val ccr = new CCR(intermediate)
+		try { evaluate( setting(chk, ccr.top) :: Nil); false }
+		catch { case e: Exception => true }
+	}
+
+	def tests = 
+		for(i <- 0 to 5; k <- Seq(a, b)) yield {
+			val expected = expectedValues(2*i + (if(k == a) 0 else 1))
+			checkKey[Int]( ScopedKey( Scope(i), k ), expected, applied)
+		}
+
 	lazy val expectedValues = None :: None :: None :: None :: None :: None :: Some(3) :: None :: Some(3) :: Some(9) :: Some(4) :: Some(9) :: Nil
+
+	lazy val ch = AttributeKey[Int]("ch")
+	lazy val chk = ScopedKey( Scope(0), ch)
+	def chain(i: Int, prev: Initialize[Int]): Initialize[Int] =
+		if(i <= 0) prev else chain(i - 1, prev(_ + 1))
+
+	def chainBind(prev: Initialize[Int]): Initialize[Int] =
+		bind(prev) { v =>
+			if(v <= 0) prev else chainBind(value(v - 1) )
+		}
+	def singleIntTest(i: Initialize[Int], expected: Int) =
+	{
+		val eval = evaluate( setting( chk, i ) :: Nil )
+		checkKey( chk, Some(expected), eval )
+	}
+
+	def checkKey[T](key: ScopedKey[T], expected: Option[T], settings: Settings[Scope]) =
+	{
+		val value = settings.get( key.scope, key.key)
+		("Key: " + key) |:
+		("Value: " + value) |:
+		("Expected: " + expected) |:
+		(value == expected)
+	}
+
+	def evaluate(settings: Seq[Setting[_]]): Settings[Scope] =
+		try { make(settings)(delegates, scopeLocal, showFullKey) }
+		catch { case e => e.printStackTrace; throw e }
+}
+// This setup is a workaround for module synchronization issues 
+final class CCR(intermediate: Int)
+{
+	lazy val top = iterate(value(intermediate), intermediate)
+	def iterate(init: Initialize[Int], i: Int): Initialize[Int] =
+		bind(init) { t =>
+			if(t <= 0)
+				top
+			else
+				iterate(value(t - 1), t-1)
+		}
 }