delete empty parent directories of deleted class files. fixes #387

compile/inc/Incremental.scala

@@ -143,7 +143,7 @@ object Incremental
 
 	def prune(invalidatedSrcs: Set[File], previous: Analysis): Analysis =
 	{
-		IO.delete( invalidatedSrcs.flatMap(previous.relations.products) )
+		IO.deleteFilesEmptyDirs( invalidatedSrcs.flatMap(previous.relations.products) )
 		previous -- invalidatedSrcs
 	}
 

sbt/src/sbt-test/source-dependencies/empty-package/changes/Define1.scala

@@ -0,0 +1,3 @@
+package a.pkgName
+
+object Test

sbt/src/sbt-test/source-dependencies/empty-package/changes/Define2.scala

@@ -0,0 +1,3 @@
+package pkgName
+
+object Test

sbt/src/sbt-test/source-dependencies/empty-package/changes/Use.scala

@@ -0,0 +1,7 @@
+package a
+
+import pkgName.Test
+
+object Use {
+	val x = Test
+}

sbt/src/sbt-test/source-dependencies/empty-package/test

@@ -0,0 +1,6 @@
+$ copy-file changes/Define1.scala Define.scala
+$ copy-file changes/Use.scala Use.scala
+> compile
+
+$ copy-file changes/Define2.scala Define.scala
+> compile

util/io/IO.scala

@@ -304,6 +304,25 @@ object IO
 	/** Deletes each file or directory (recursively) in `files`.*/
 	def delete(files: Iterable[File]): Unit = files.foreach(delete)
 
+	/** Deletes each file or directory in `files` recursively.  Any empty parent directories are deleted, recursively.*/
+	def deleteFilesEmptyDirs(files: Iterable[File]): Unit =
+	{
+		def isEmptyDirectory(dir: File) = dir.isDirectory && listFiles(dir).isEmpty
+		def parents(fs: Set[File]) = fs.map(_.getParentFile)
+		def deleteEmpty(dirs: Set[File])
+		{
+			val empty = dirs filter isEmptyDirectory
+			if(empty.nonEmpty)  // looks funny, but this is true if at least one of `dirs` is an empty directory
+			{
+				empty foreach { _.delete() }
+				deleteEmpty(parents(empty))
+			}
+		}
+
+		delete(files)
+		deleteEmpty(parents(files.toSet))
+	}
+
 	/** Deletes `file`, recursively if it is a directory. */
 	def delete(file: File)
 	{