Added conflict report and unit tests

main/src/main/scala/sbt/Plugins.scala

@@ -64,6 +64,8 @@ abstract class AutoPlugin extends Plugins.Basic with PluginsFunctions
 
 	val label: String = getClass.getName.stripSuffix("$")
 
+	override def toString: String = label
+
 	/** The [[Configuration]]s to add to each project that activates this AutoPlugin.*/
 	def projectConfigurations: Seq[Configuration] = Nil
 
@@ -169,8 +171,7 @@ object Plugins extends PluginsFunctions
 						val forbidden: Set[AutoPlugin] = (selectedPlugins flatMap { Plugins.asExclusions }).toSet
 						val c = selectedPlugins.toSet & forbidden
 						if (!c.isEmpty) {
-							val listString = (c map {_.label}).mkString(", ")
-							throw AutoPluginException(s"Contradiction in selected plugins.  These plguins were both included and excluded: ${listString}")
+							exlusionConflictError(requestedPlugins, selectedPlugins, c.toSeq sortBy {_.label})
 						}
 						val retval = topologicalSort(selectedPlugins, log)
 						log.debug(s"  :: sorted deduced result: ${retval.toString}")
@@ -193,7 +194,7 @@ object Plugins extends PluginsFunctions
 		doSort(roots, nonRoots, ns.size * ns.size + 1)
 	}
 	private[sbt] def translateMessage(e: LogicException) = e match {
-		case ic: InitialContradictions => s"Contradiction in selected plugins.  These plguins were both included and excluded: ${literalsString(ic.literals.toSeq)}"
+		case ic: InitialContradictions => s"Contradiction in selected plugins.  These plugins were both included and excluded: ${literalsString(ic.literals.toSeq)}"
 		case io: InitialOverlap => s"Cannot directly enable plugins.  Plugins are enabled when their required plugins are satisifed.  The directly selected plugins were: ${literalsString(io.literals.toSeq)}"
 		case cn: CyclicNegation => s"Cycles in plugin requirements cannot involve excludes.  The problematic cycle is: ${literalsString(cn.cycle)}"
 	}
@@ -208,6 +209,29 @@ object Plugins extends PluginsFunctions
 		val message = s"Plugin$ns provided by multiple AutoPlugins:$nl${dupStrings.mkString(nl)}"
 		throw AutoPluginException(message)
 	}
+	private[this] def exlusionConflictError(requested: Plugins, selected: Seq[AutoPlugin], conflicting: Seq[AutoPlugin]) {
+		def listConflicts(ns: Seq[AutoPlugin]) = (ns map { c =>
+			val reasons = (if (flatten(requested) contains c) List("requested")
+							else Nil) ++
+				(if (c.requires != empty && c.trigger == allRequirements) List(s"enabled by ${c.requires.toString}")
+					else Nil) ++
+				{
+					val reqs = selected filter { x => asRequirements(x) contains c }
+					if (!reqs.isEmpty) List(s"""required by ${reqs.mkString(", ")}""")
+					else Nil
+				} ++
+				{
+					val exs = selected filter { x => asExclusions(x) contains c }
+					if (!exs.isEmpty) List(s"""excluded by ${exs.mkString(", ")}""")
+					else Nil
+				}
+			s"""  - conflict: ${c.label} is ${reasons.mkString("; ")}"""
+		}).mkString("\n")
+		throw AutoPluginException(s"""Contradiction in enabled plugins:
+  - requested: ${requested.toString}
+  - enabled: ${selected.mkString(", ")}
+${listConflicts(conflicting)}""")
+	}
 
 	private[sbt] final object Empty extends Plugins {
 		def &&(o: Basic): Plugins = o
@@ -225,7 +249,7 @@ object Plugins extends PluginsFunctions
 	}
 	private[sbt] final case class And(plugins: List[Basic]) extends Plugins {
 		def &&(o: Basic): Plugins = And(o :: plugins)
-		override def toString = plugins.mkString(", ")
+		override def toString = plugins.mkString(" && ")
 	}
 	private[sbt] def and(a: Plugins, b: Plugins) = b match {
 		case Empty => a

main/src/test/scala/PluginsTest.scala

@@ -0,0 +1,96 @@
+package sbt
+
+import java.io.File
+import org.specs2._
+import mutable.Specification
+
+object PluginsTest extends Specification
+{
+	import AI._
+
+	"Auto plugin" should {
+		"enable plugins with trigger=allRequirements AND requirements met" in {
+			deducePlugin(A && B, log) must contain(Q)
+		}
+		"enable transive plugins with trigger=allRequirements AND requirements met" in {
+			deducePlugin(A && B, log) must contain(R)
+		}
+		"order enable plugins after required plugins" in {
+			val ns = deducePlugin(A && B, log)
+			( (ns indexOf Q) must beGreaterThan(ns indexOf A) ) and
+			( (ns indexOf Q) must beGreaterThan(ns indexOf B) ) and
+			( (ns indexOf R) must beGreaterThan(ns indexOf A) ) and
+			( (ns indexOf R) must beGreaterThan(ns indexOf B) ) and
+			( (ns indexOf R) must beGreaterThan(ns indexOf Q) )	
+		}
+		"not enable plugins with trigger=allRequirements but conflicting requirements" in {
+			deducePlugin(A && B, log) must not contain(S)
+		}
+		"enable plugins that are required by the requested plugins" in {
+			val ns = deducePlugin(Q, log)
+			(ns must contain(A)) and
+			(ns must contain(B))
+		}
+		"throw an AutoPluginException on conflicting requirements" in {
+			deducePlugin(S, log) must throwAn[AutoPluginException](message = """Contradiction in enabled plugins:
+  - requested: sbt.AI\$S
+  - enabled: sbt.AI\$S, sbt.AI\$Q, sbt.AI\$R, sbt.AI\$B, sbt.AI\$A
+  - conflict: sbt.AI\$R is enabled by sbt.AI\$Q; excluded by sbt.AI\$S""")
+		}
+		"generates a detailed report on conflicting requirements" in {
+			deducePlugin(T && U, log) must throwAn[AutoPluginException](message = """Contradiction in enabled plugins:
+  - requested: sbt.AI\$T && sbt.AI\$U
+  - enabled: sbt.AI\$U, sbt.AI\$T, sbt.AI\$A, sbt.AI\$Q, sbt.AI\$R, sbt.AI\$B
+  - conflict: sbt.AI\$Q is enabled by sbt.AI\$A && sbt.AI\$B; required by sbt.AI\$T, sbt.AI\$R; excluded by sbt.AI\$U
+  - conflict: sbt.AI\$R is enabled by sbt.AI\$Q; excluded by sbt.AI\$T""")
+		}
+	}
+}
+
+object AI
+{
+	lazy val allPlugins: List[AutoPlugin] = List(A, B, Q, R, S, T, U)
+	lazy val deducePlugin = Plugins.deducer(allPlugins)
+	lazy val log = Logger.Null
+
+	trait EmptyAutoPlugin extends AutoPlugin {
+		def requires = empty
+		def trigger = noTrigger
+	}
+	object A extends EmptyAutoPlugin
+	object B extends EmptyAutoPlugin
+
+	object Q extends AutoPlugin
+	{
+		def requires: Plugins = A && B
+		def trigger = allRequirements
+	}
+
+	object R extends AutoPlugin
+	{
+		def requires = Q
+		def trigger = allRequirements
+	}
+
+	object S extends AutoPlugin
+	{
+		def requires = Q && !R
+		def trigger = allRequirements
+	}
+
+	// This is an opt-in plugin with a requirement
+	// Unless explicitly loaded by the build user, this will not be activated.
+	object T extends AutoPlugin
+	{
+		def requires = Q && !R
+		def trigger = noTrigger
+	}
+
+	// This is an opt-in plugin with a requirement
+	// Unless explicitly loaded by the build user, this will not be activated.
+	object U extends AutoPlugin
+	{
+		def requires = A && !Q
+		def trigger = noTrigger
+	}
+}