Make REPL tests capture all produced output

It used to capture output only from 'println(String | Object)'

compiler/src/dotty/tools/repl/ReplDriver.scala

@@ -81,8 +81,8 @@ case class Completions(cursor: Int,
 
 /** Main REPL instance, orchestrating input, compilation and presentation */
 class ReplDriver(settings: Array[String],
-                 protected val out: PrintStream = Console.out,
-                 protected val classLoader: Option[ClassLoader] = None) extends Driver {
+                 out: PrintStream = Console.out,
+                 classLoader: Option[ClassLoader] = None) extends Driver {
 
   /** Overridden to `false` in order to not have to give sources on the
    *  commandline

compiler/test/dotty/tools/repl/ReplTest.scala

@@ -11,38 +11,20 @@ import org.junit.Assert.fail
 import dotc.reporting.diagnostic.MessageContainer
 import results.Result
 
-sealed class NullPrintStream extends ByteArrayOutputStream {
-  override def write(b: Int) = ()
-  override def write(b: Array[Byte], off: Int, len: Int) = ()
-  override def writeTo(out: OutputStream) = ()
-}
-
-sealed class StoringPrintStream extends PrintStream(new NullPrintStream) {
-  private[this] var sb = new StringBuilder
-
-  override def println(obj: Object) =
-    println(obj.toString)
-
-  override def println(str: String) = {
-    sb.append(str)
-    sb += '\n'
-  }
 
-  def flushStored(): String = {
-    val str = sb.toString
-    sb = new StringBuilder
-    str
-  }
-}
-
-class ReplTest extends ReplDriver(
+class ReplTest private (out: ByteArrayOutputStream) extends ReplDriver(
   Array("-classpath", List(Jars.dottyLib, Jars.dottyInterfaces).mkString(":"), "-color:never"),
-  new StoringPrintStream
+  new PrintStream(out)
 ) with MessageRendering {
 
-  /** Get the stored output from `out`, resetting the `StoringPrintStream` */
-  def storedOutput(): String =
-    stripColor(out.asInstanceOf[StoringPrintStream].flushStored())
+  def this() = this(new ByteArrayOutputStream)
+
+  /** Get the stored output from `out`, resetting the buffer */
+  def storedOutput(): String = {
+    val output = stripColor(out.toString)
+    out.reset()
+    output
+  }
 
   protected implicit def toParsed(expr: String)(implicit state: State): Parsed = {
     implicit val ctx = state.run.runContext

compiler/test/dotty/tools/repl/ScriptedTests.scala

@@ -22,14 +22,14 @@ class ScriptedTests extends ReplTest with MessageRendering {
 
   private def testFile(f: JFile): Unit = {
     val prompt = "scala>"
-    val lines = Source.fromFile(f).getLines.buffered
+    val lines = Source.fromFile(f).getLines().buffered
+
+    assert(lines.head.startsWith(prompt),
+      s"""Each file has to start with the prompt: "$prompt"""")
 
     def extractInputs(prompt: String): List[String] = {
       val input = lines.next()
 
-      assert(input.startsWith(prompt),
-        s"""Each file has to start with the prompt: "$prompt"""")
-
       if (!input.startsWith(prompt)) extractInputs(prompt)
       else if (lines.hasNext) {
         // read lines and strip trailing whitespace:
@@ -60,7 +60,7 @@ class ScriptedTests extends ReplTest with MessageRendering {
       }
 
     val expectedOutput =
-      Source.fromFile(f).getLines.flatMap(filterEmpties).mkString("\n")
+      Source.fromFile(f).getLines().flatMap(filterEmpties).mkString("\n")
     val actualOutput = {
       resetToInitial()
       init()