From 9d6a4f70f7104e32df8163fbe76caba74773920b Mon Sep 17 00:00:00 2001
From: Mark Harrah <dmharrah@gmail.com>
Date: Wed, 24 Nov 2010 14:09:02 -0500
Subject: [PATCH] additional utility methods

---
 util/io/IO.scala         | 11 ++++++++++-
 util/io/PathMapper.scala |  8 +++++++-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/util/io/IO.scala b/util/io/IO.scala
index 6b6350237..07537d92a 100644
--- a/util/io/IO.scala
+++ b/util/io/IO.scala
@@ -13,7 +13,7 @@ import java.util.Properties
 import java.util.jar.{Attributes, JarEntry, JarFile, JarInputStream, JarOutputStream, Manifest}
 import java.util.zip.{CRC32, GZIPOutputStream, ZipEntry, ZipFile, ZipInputStream, ZipOutputStream}
 import scala.collection.immutable.TreeSet
-import scala.collection.mutable.HashSet
+import scala.collection.mutable.{HashMap,HashSet}
 import scala.reflect.{Manifest => SManifest}
 import Function.tupled
 
@@ -244,6 +244,15 @@ object IO
 
 	private[sbt] def jars(dir: File): Iterable[File] = listFiles(dir, GlobFilter("*.jar"))
 
+	def deleteIfEmpty(dirs: collection.Set[File]): Unit =
+	{
+		val isEmpty = new HashMap[File, Boolean]
+		def visit(f: File): Boolean = isEmpty.getOrElseUpdate(f, dirs(f) && f.isDirectory && (f.listFiles forall visit) )
+
+		dirs foreach visit
+		for( (f, true) <- isEmpty) f.delete
+	}
+
 	def delete(files: Iterable[File]): Unit = files.foreach(delete)
 	def delete(file: File)
 	{
diff --git a/util/io/PathMapper.scala b/util/io/PathMapper.scala
index fd0327225..b4a8b20d1 100644
--- a/util/io/PathMapper.scala
+++ b/util/io/PathMapper.scala
@@ -3,7 +3,7 @@
  */
 package sbt
 
-import java.io.File
+	import java.io.File
 
 trait Mapper
 {
@@ -51,4 +51,10 @@ trait Alternatives
 		new Alternative[A,B] { def | (g: A => Option[B]) =
 			(a: A) => f(a) orElse g(a)
 		}
+	final def alternatives[A,B](alts: Seq[A => Option[B]]): A => Option[B] =
+		alts match
+		{
+			case Seq(f, fs @ _*) => f | alternatives(fs)
+			case Seq() => a => None
+		}
 }
\ No newline at end of file