From 868196e6522f4fa67f038ab0d99fb18e661c4ac7 Mon Sep 17 00:00:00 2001
From: Mark Harrah <dmharrah@gmail.com>
Date: Mon, 5 Mar 2012 13:40:17 -0500
Subject: [PATCH] delete empty parent directories of deleted class files. fixes
 #387

---
 compile/inc/Incremental.scala                 |  2 +-
 .../empty-package/changes/Define1.scala       |  3 +++
 .../empty-package/changes/Define2.scala       |  3 +++
 .../empty-package/changes/Use.scala           |  7 +++++++
 .../source-dependencies/empty-package/test    |  6 ++++++
 util/io/IO.scala                              | 19 +++++++++++++++++++
 6 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 sbt/src/sbt-test/source-dependencies/empty-package/changes/Define1.scala
 create mode 100644 sbt/src/sbt-test/source-dependencies/empty-package/changes/Define2.scala
 create mode 100644 sbt/src/sbt-test/source-dependencies/empty-package/changes/Use.scala
 create mode 100644 sbt/src/sbt-test/source-dependencies/empty-package/test

diff --git a/compile/inc/Incremental.scala b/compile/inc/Incremental.scala
index 4c35b6b6a..60fe84d69 100644
--- a/compile/inc/Incremental.scala
+++ b/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
 	}
 
diff --git a/sbt/src/sbt-test/source-dependencies/empty-package/changes/Define1.scala b/sbt/src/sbt-test/source-dependencies/empty-package/changes/Define1.scala
new file mode 100644
index 000000000..9317a8425
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/empty-package/changes/Define1.scala
@@ -0,0 +1,3 @@
+package a.pkgName
+
+object Test
diff --git a/sbt/src/sbt-test/source-dependencies/empty-package/changes/Define2.scala b/sbt/src/sbt-test/source-dependencies/empty-package/changes/Define2.scala
new file mode 100644
index 000000000..ed2d7ae8a
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/empty-package/changes/Define2.scala
@@ -0,0 +1,3 @@
+package pkgName
+
+object Test
diff --git a/sbt/src/sbt-test/source-dependencies/empty-package/changes/Use.scala b/sbt/src/sbt-test/source-dependencies/empty-package/changes/Use.scala
new file mode 100644
index 000000000..b4d87c711
--- /dev/null
+++ b/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
+}
diff --git a/sbt/src/sbt-test/source-dependencies/empty-package/test b/sbt/src/sbt-test/source-dependencies/empty-package/test
new file mode 100644
index 000000000..1577ef521
--- /dev/null
+++ b/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
diff --git a/util/io/IO.scala b/util/io/IO.scala
index eb478333b..1484b7ed2 100644
--- a/util/io/IO.scala
+++ b/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)
 	{