From 6b7fbfe77961ab9d3fa7a9ea7f742f8b3935dde7 Mon Sep 17 00:00:00 2001
From: Mark Harrah <dmharrah@gmail.com>
Date: Wed, 13 Mar 2013 12:40:03 -0400
Subject: [PATCH] Provided details of why external binaries are detected as
 modified in incremental compiler debug output.

---
 .../src/main/scala/sbt/inc/Incremental.scala  | 48 +++++++++++++------
 1 file changed, 34 insertions(+), 14 deletions(-)

diff --git a/compile/inc/src/main/scala/sbt/inc/Incremental.scala b/compile/inc/src/main/scala/sbt/inc/Incremental.scala
index e9722f294..ec6fbc1f7 100644
--- a/compile/inc/src/main/scala/sbt/inc/Incremental.scala
+++ b/compile/inc/src/main/scala/sbt/inc/Incremental.scala
@@ -21,14 +21,14 @@ object Incremental
 		log: Logger,
 		options: IncOptions)(implicit equivS: Equiv[Stamp]): (Boolean, Analysis) =
 	{
-		val initialChanges = changedInitial(entry, sources, previous, current, forEntry, options)
+		val initialChanges = changedInitial(entry, sources, previous, current, forEntry, options, log)
 		val binaryChanges = new DependencyChanges {
 			val modifiedBinaries = initialChanges.binaryDeps.toArray
 			val modifiedClasses = initialChanges.external.modified.toArray
 			def isEmpty = modifiedBinaries.isEmpty && modifiedClasses.isEmpty
 		}
 		val initialInv = invalidateInitial(previous.relations, initialChanges, log)
-		log.debug("Initially invalidated: " + initialInv)
+		log.debug("All initially invalidated sources: " + initialInv + "\n")
 		val analysis = manageClassfiles(options) { classfileManager =>
 			cycle(initialInv, sources, binaryChanges, previous, doCompile, classfileManager, 1, log, options)
 		}
@@ -125,14 +125,14 @@ object Incremental
   }
 
 	def changedInitial(entry: String => Option[File], sources: Set[File], previousAnalysis: Analysis, current: ReadStamps,
-	    forEntry: File => Option[Analysis], options: IncOptions)(implicit equivS: Equiv[Stamp]): InitialChanges =
+	   forEntry: File => Option[Analysis], options: IncOptions, log: Logger)(implicit equivS: Equiv[Stamp]): InitialChanges =
 	{
 		val previous = previousAnalysis.stamps
 		val previousAPIs = previousAnalysis.apis
 
 		val srcChanges = changes(previous.allInternalSources.toSet, sources,  f => !equivS.equiv( previous.internalSource(f), current.internalSource(f) ) )
 		val removedProducts = previous.allProducts.filter( p => !equivS.equiv( previous.product(p), current.product(p) ) ).toSet
-		val binaryDepChanges = previous.allBinaries.filter( externalBinaryModified(entry, forEntry, previous, current)).toSet
+		val binaryDepChanges = previous.allBinaries.filter( externalBinaryModified(entry, forEntry, previous, current, log)).toSet
 		val extChanges = changedIncremental(previousAPIs.allExternals, previousAPIs.externalAPI _, currentExternalAPI(entry, forEntry), options)
 
 		InitialChanges(srcChanges, removedProducts, binaryDepChanges, extChanges )
@@ -252,18 +252,38 @@ object Incremental
 		previous -- invalidatedSrcs
 	}
 
-	def externalBinaryModified(entry: String => Option[File], analysis: File => Option[Analysis], previous: Stamps, current: ReadStamps)(implicit equivS: Equiv[Stamp]): File => Boolean =
+	def externalBinaryModified(entry: String => Option[File], analysis: File => Option[Analysis], previous: Stamps, current: ReadStamps, log: Logger)(implicit equivS: Equiv[Stamp]): File => Boolean =
 		dependsOn =>
-			analysis(dependsOn).isEmpty &&
-			orTrue(
-				for {
-					name <- previous.className(dependsOn)
-					e <- entry(name)
-				} yield {
-					val resolved = Locate.resolve(e, name)
-					(resolved.getCanonicalPath != dependsOn.getCanonicalPath) || !equivS.equiv(previous.binary(dependsOn), current.binary(resolved))
+		{
+			def inv(reason: String): Boolean = {
+				log.debug("Invalidating " + dependsOn.getCanonicalPath + ": " + reason)
+				true
+			}
+			def entryModified(className: String, classpathEntry: File): Boolean =
+			{
+				val resolved = Locate.resolve(classpathEntry, className)
+				if(resolved.getCanonicalPath != dependsOn.getCanonicalPath)
+					inv("class " + className + " now provided by " + resolved.getCanonicalPath)
+				else {
+					val previousStamp = previous.binary(dependsOn)
+					val resolvedStamp = current.binary(resolved)
+					if(equivS.equiv(previousStamp, resolvedStamp))
+						false
+					else
+						inv("stamp changed from " + previousStamp + " to " + resolvedStamp)
 				}
-			)
+			}
+
+			analysis(dependsOn).isEmpty && {
+				previous.className(dependsOn) match {
+					case None => inv("no class name was mapped for it.")
+					case Some(name) => entry(name) match {
+						case None => inv("could not find class " + name + " on the classpath.")
+						case Some(e) => entryModified(name, e)
+					}
+				}
+			}
+		}
 
 	def currentExternalAPI(entry: String => Option[File], forEntry: File => Option[Analysis]): String => Source =
 		className =>