apply javac log level approach to directJavac

util/log/LoggerWriter.scala

@@ -5,11 +5,13 @@ package sbt
 
 /** Provides a `java.io.Writer` interface to a `Logger`.  Content is line-buffered and logged at `level`.
 * A line is delimited by `nl`, which is by default the platform line separator.*/
-class LoggerWriter(delegate: Logger, level: Level.Value, nl: String) extends java.io.Writer
+class LoggerWriter(delegate: Logger, unbufferedLevel: Option[Level.Value], nl: String = System.getProperty("line.separator")) extends java.io.Writer
 {
-	def this(delegate: Logger, level: Level.Value) = this(delegate, level, System.getProperty("line.separator"))
+	def this(delegate: Logger, level: Level.Value) = this(delegate, Some(level))
+	def this(delegate: Logger) = this(delegate, None)
 	
 	private[this] val buffer = new StringBuilder
+	private[this] val lines = new collection.mutable.ListBuffer[String]
 
 	override def close() = flush()
 	override def flush(): Unit =
@@ -20,6 +22,12 @@ class LoggerWriter(delegate: Logger, level: Level.Value, nl: String) extends jav
 				buffer.clear()
 			}
 		}
+	def flushLines(level: Level.Value): Unit =
+		synchronized {
+			for(line <- lines)
+				delegate.log(level, line)
+			lines.clear()
+		}
 	override def write(content: Array[Char], offset: Int, length: Int): Unit =
 		synchronized {
 			buffer.appendAll(content, offset, length)
@@ -36,5 +44,8 @@ class LoggerWriter(delegate: Logger, level: Level.Value, nl: String) extends jav
 			process()
 		}
 	}
-	private[this] def log(s: String): Unit  =  delegate.log(level, s)
+	private[this] def log(s: String): Unit = unbufferedLevel match {
+		case None => lines += s
+		case Some(level) => delegate.log(level, s)
+	}
 }