From 29dd76da8595b810cec7e509c1f34d8bd7212a76 Mon Sep 17 00:00:00 2001
From: Mark Harrah <dmharrah@gmail.com>
Date: Tue, 21 Aug 2012 12:26:11 -0400
Subject: [PATCH] defer opening logging output files until an actual write

---
 tasks/standard/Streams.scala |  2 +-
 util/io/DeferredWriter.scala | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 util/io/DeferredWriter.scala

diff --git a/tasks/standard/Streams.scala b/tasks/standard/Streams.scala
index f39cee152..a8e6c9afd 100644
--- a/tasks/standard/Streams.scala
+++ b/tasks/standard/Streams.scala
@@ -77,7 +77,7 @@ object Streams
 				make(a, sid)(f => new BufferedInputStream(new FileInputStream(f)))
 	
 			def text(sid: String = default): PrintWriter =
-				make(a, sid)(f => new PrintWriter(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(f), IO.defaultCharset))) )
+				make(a, sid)(f => new PrintWriter(new DeferredWriter(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(f), IO.defaultCharset)))) )
 
 			def binary(sid: String = default): BufferedOutputStream =
 				make(a, sid)(f => new BufferedOutputStream(new FileOutputStream(f)))
diff --git a/util/io/DeferredWriter.scala b/util/io/DeferredWriter.scala
new file mode 100644
index 000000000..3e93564a2
--- /dev/null
+++ b/util/io/DeferredWriter.scala
@@ -0,0 +1,29 @@
+package sbt
+
+	import java.io.Writer
+
+final class DeferredWriter(make: => Writer) extends Writer
+{
+	private[this] var opened = false
+	private[this] var delegate0: Writer = _
+	private[this] def delegate: Writer = synchronized {
+		if(delegate0 eq null) {
+			delegate0 = make
+			opened = true
+		}
+		delegate0
+	}
+	override def close() = synchronized {
+		if(opened) delegate0.close()
+	}
+
+	override def append(c: Char): Writer = delegate.append(c)
+	override def append(csq: CharSequence): Writer = delegate.append(csq)
+	override def append(csq: CharSequence, start: Int, end: Int): Writer = delegate.append(csq, start, end)
+	override def flush() = delegate.flush()
+	override def write(cbuf: Array[Char]) = delegate.write(cbuf)
+	override def write(cbuf: Array[Char], off: Int, len: Int): Unit = delegate.write(cbuf, off, len)
+	override def write(c: Int): Unit = delegate.write(c)
+	override def write(s: String): Unit = delegate.write(s)
+	override def write(s: String, off: Int, len: Int): Unit = delegate.write(s, off, len)
+}
\ No newline at end of file