Improve Xprint

project/Build.scala

@@ -100,6 +100,7 @@ object DottyBuild extends Build {
                                   "org.scala-lang.modules" %% "scala-partest" % "1.0.11" % "test",
                                   "com.novocode" % "junit-interface" % "0.11" % "test",
                                   "jline" % "jline" % "2.12",
+                                  "com.googlecode.java-diff-utils" % "diffutils" % "1.3.0",
                                   "com.typesafe.sbt" % "sbt-interface" % sbtVersion.value),
       // enable improved incremental compilation algorithm
       incOptions := incOptions.value.withNameHashing(true),

src/dotty/tools/dotc/Run.scala

@@ -2,14 +2,20 @@ package dotty.tools
 package dotc
 
 import core._
-import Contexts._, Periods._, Symbols._, Phases._, Decorators._
+import Contexts._
+import Periods._
+import Symbols._
+import Phases._
+import Decorators._
 import dotty.tools.dotc.transform.TreeTransforms.TreeTransformer
 import io.PlainFile
-import util.{SourceFile, NoSource, Stats, SimpleMap}
+import util._
 import reporting.Reporter
 import transform.TreeChecker
 import rewrite.Rewrites
 import java.io.{BufferedWriter, OutputStreamWriter}
+
+import scala.annotation.tailrec
 import scala.reflect.io.VirtualFile
 import scala.util.control.NonFatal
 
@@ -56,26 +62,48 @@ class Run(comp: Compiler)(implicit ctx: Context) {
     val phases = ctx.squashPhases(ctx.phasePlan,
       ctx.settings.Yskip.value, ctx.settings.YstopBefore.value, ctx.settings.YstopAfter.value, ctx.settings.Ycheck.value)
     ctx.usePhases(phases)
+    var lastPrintedTree: PrintedTree = NoPrintedTree
     for (phase <- ctx.allPhases)
       if (!ctx.reporter.hasErrors) {
         val start = System.currentTimeMillis
         units = phase.runOn(units)
-        def foreachUnit(op: Context => Unit)(implicit ctx: Context): Unit =
-          for (unit <- units) op(ctx.fresh.setPhase(phase.next).setCompilationUnit(unit))
-        if (ctx.settings.Xprint.value.containsPhase(phase))
-          foreachUnit(printTree)
+        if (ctx.settings.Xprint.value.containsPhase(phase)) {
+          for (unit <- units) {
+            lastPrintedTree =
+              printTree(lastPrintedTree)(ctx.fresh.setPhase(phase.next).setCompilationUnit(unit))
+          }
+        }
         ctx.informTime(s"$phase ", start)
       }
     if (!ctx.reporter.hasErrors) Rewrites.writeBack()
   }
 
-  private def printTree(ctx: Context) = {
+  private sealed trait PrintedTree
+  private final case class SomePrintedTree(phase: String, tree: String) extends PrintedTree
+  private object NoPrintedTree extends PrintedTree
+
+  private def printTree(last: PrintedTree)(implicit ctx: Context): PrintedTree = {
     val unit = ctx.compilationUnit
     val prevPhase = ctx.phase.prev // can be a mini-phase
     val squashedPhase = ctx.squashed(prevPhase)
+    val treeString = unit.tpdTree.show
+
+    ctx.echo(s"result of $unit after $squashedPhase:")
 
-    ctx.echo(s"result of $unit after ${squashedPhase}:")
-    ctx.echo(unit.tpdTree.show(ctx))
+    last match {
+      case SomePrintedTree(phase, lastTreeSting) if lastTreeSting != treeString =>
+        val diff = DiffUtil.mkColoredCodeDiff(treeString, lastTreeSting, ctx.settings.XprintDiffDel.value)
+        ctx.echo(diff)
+        SomePrintedTree(squashedPhase.toString, treeString)
+
+      case SomePrintedTree(phase, lastTreeSting) =>
+        ctx.echo("  Unchanged since " + phase)
+        last
+
+      case NoPrintedTree =>
+        ctx.echo(treeString)
+        SomePrintedTree(squashedPhase.toString, treeString)
+    }
   }
 
   def compile(sourceCode: String): Unit = {

src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -85,6 +85,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val writeICode = PhasesSetting("-Xprint-icode", "Log internal icode to *.icode files after", "icode")
   val Xprintpos = BooleanSetting("-Xprint-pos", "Print tree positions, as offsets.")
   val printtypes = BooleanSetting("-Xprint-types", "Print tree types (debugging option).")
+  val XprintDiffDel = BooleanSetting("-Xprint-diff-del", "Print deleted parts of the tree since last print.")
   val prompt = BooleanSetting("-Xprompt", "Display a prompt after each error (debugging option).")
   val script = StringSetting("-Xscript", "object", "Treat the source file as a script and wrap it in a main method.", "")
   val mainClass = StringSetting("-Xmain-class", "path", "Class for manifest's Main-Class entry (only useful with -d <jar>)", "")

src/dotty/tools/dotc/util/DiffUtil.scala

@@ -0,0 +1,66 @@
+package dotty.tools.dotc.util
+
+import scala.annotation.tailrec
+import difflib._
+
+object DiffUtil {
+
+  private final val ANSI_DEFAULT = "\u001B[0m"
+  private final val ANSI_RED = "\u001B[31m"
+  private final val ANSI_GREEN = "\u001B[32m"
+  private final val ANSI_YELLOW = "\u001B[33m"
+  private final val ANSI_MAGENTA = "\u001B[35m"
+
+  def mkColoredCodeDiff(code: String, lastCode: String, printDiffDel: Boolean): String = {
+    import scala.collection.JavaConversions._
+
+    @tailrec def split(str: String, acc: List[String]): List[String] = {
+      if (str == "") {
+        acc.reverse
+      } else {
+        val head = str.charAt(0)
+        val (token, rest) = if (Character.isAlphabetic(head) || Character.isDigit(head)) {
+          str.span(c => Character.isAlphabetic(c) || Character.isDigit(c))
+        } else if (Character.isMirrored(head) || Character.isWhitespace(head)) {
+          str.splitAt(1)
+        } else {
+          str.span { c =>
+            !Character.isAlphabetic(c) && !Character.isDigit(c) &&
+              !Character.isMirrored(c) && !Character.isWhitespace(c)
+          }
+        }
+        split(rest, token :: acc)
+      }
+    }
+
+    val lines = split(code, Nil).toArray
+    val diff = DiffUtils.diff(split(lastCode, Nil), lines.toList)
+
+    for (delta <- diff.getDeltas) {
+      val pos = delta.getRevised.getPosition
+      val endPos = pos + delta.getRevised.getLines.size - 1
+
+      delta.getType.toString match { // Issue #1355 forces us to use the toString
+        case "INSERT" =>
+          lines(pos) = ANSI_GREEN + lines(pos)
+          lines(endPos) = lines(endPos) + ANSI_DEFAULT
+
+        case "CHANGE" =>
+          val old = if (!printDiffDel) "" else
+            ANSI_MAGENTA + delta.getOriginal.getLines.mkString + ANSI_DEFAULT
+          lines(pos) = old + ANSI_YELLOW + lines(pos)
+          lines(endPos) = lines(endPos) + ANSI_DEFAULT
+
+        case "DELETE" if printDiffDel =>
+          val deleted = delta.getOriginal.getLines.mkString
+          if (!deleted.forall(Character.isWhitespace)) {
+            lines(pos) = ANSI_RED + deleted + ANSI_DEFAULT + lines(pos)
+          }
+
+        case _ =>
+      }
+    }
+
+    lines.mkString
+  }
+}