move error processing to complete/

util/complete/Parser.scala

@@ -277,6 +277,12 @@ trait ParserMain
 		def unapply[A,B](t: (A,B)): Some[(A,B)] = Some(t)
 	}
 
+	def parse[T](str: String, parser: Parser[T]): Either[String, T] =
+		Parser.result(parser, str).left.map { failures =>
+			val (msgs,pos) = failures()
+			ProcessError(str, msgs, pos)
+		}
+
 	// intended to be temporary pending proper error feedback
 	def result[T](p: Parser[T], s: String): Either[() => (Seq[String],Int), T] =
 	{

util/complete/ProcessError.scala

@@ -0,0 +1,30 @@
+package sbt.complete
+
+object ProcessError
+{
+	def apply(command: String, msgs: Seq[String], index: Int): String =
+	{
+		val (line, modIndex) = extractLine(command, index)
+		val point = pointerSpace(command, modIndex)
+		msgs.mkString("\n") + "\n" + line + "\n" + point + "^"
+	}
+	def extractLine(s: String, i: Int): (String, Int) =
+	{
+		val notNewline = (c: Char) => c != '\n' && c != '\r'
+		val left = takeRightWhile( s.substring(0, i) )( notNewline )
+		val right = s substring i takeWhile notNewline
+		(left + right, left.length)
+	}
+	def takeRightWhile(s: String)(pred: Char => Boolean): String =
+	{
+		def loop(i: Int): String =
+			if(i < 0)
+				s
+			else if( pred(s(i)) )
+				loop(i-1)
+			else
+				s.substring(i+1)
+		loop(s.length - 1)
+	}
+	def pointerSpace(s: String, i: Int): String  =	(s take i) map { case '\t' => '\t'; case _ => ' ' } mkString;
+}