Add smart comment formatting in ConsoleReporter

Author: felixmulder

src/dotty/tools/dotc/reporting/ConsoleReporter.scala

@@ -8,6 +8,7 @@ import core.Contexts._
 import Reporter._
 import java.io.{ BufferedReader, IOException, PrintWriter }
 import scala.reflect.internal.util._
+import printing.SyntaxHighlighting._
 
 /**
  * This class implements a Reporter that displays messages on a text
@@ -21,34 +22,76 @@ class ConsoleReporter(
   /** maximal number of error messages to be printed */
   protected def ErrorLimit = 100
 
-  def printSourceLine(pos: SourcePosition) =
-    printMessage(pos.lineContent.stripLineEnd)
+  def sourceLine(pos: SourcePosition): (String, Int) = {
+    val lineNum = s"${pos.line}:"
+    (lineNum + hl"${pos.lineContent.stripLineEnd}", lineNum.length)
+  }
+
+  def columnMarker(pos: SourcePosition, offset: Int) =
+    if (pos.startLine == pos.endLine) {
+      val whitespace = " " * (pos.column + offset)
+      val carets =
+        AnnotationColor +
+        ("^" * math.max(1, pos.endColumn - pos.startColumn)) +
+        NoColor
+
+      whitespace + carets
+    } else {
+      " " * (pos.column + offset) + AnnotationColor + "^" + NoColor
+    }
+
+  def errorMsg(pos: SourcePosition, msg: String, offset: Int)(implicit ctx: Context) = {
+    var hasLongLines = false
+    val leastWhitespace = msg.lines.foldLeft(Int.MaxValue) { (minPad, line) =>
+      val lineLength =
+        line.replaceAll("\u001B\\[[;\\d]*m", "").length
+      val padding =
+        math.min(math.max(0, ctx.settings.pageWidth.value - offset - lineLength), offset + pos.startColumn)
+
+      if (padding < minPad) padding
+      else minPad
+    }
 
-  def printColumnMarker(pos: SourcePosition) =
-    if (pos.exists) { printMessage(" " * pos.column + "^") }
+    msg
+      .lines
+      .map { line => " " * leastWhitespace + line }
+      .mkString(sys.props("line.separator"))
+  }
+
+  def posStr(pos: SourcePosition, kind: String)(implicit ctx: Context) =
+    if (pos.exists) {
+      val file = pos.source.file.toString
+
+      s"${Console.CYAN}$kind: $file " +
+      "-" * math.max(ctx.settings.pageWidth.value - file.length - kind.length - 1, 0) +
+      NoColor
+    }
+    else ""
 
   /** Prints the message. */
   def printMessage(msg: String): Unit = { writer.print(msg + "\n"); writer.flush() }
 
   /** Prints the message with the given position indication. */
-  def printMessageAndPos(msg: String, pos: SourcePosition)(implicit ctx: Context): Unit = {
-    val posStr = if (pos.exists) s"$pos: " else ""
-    printMessage(posStr + msg)
+  def printMessageAndPos(msg: String, pos: SourcePosition, kind: String = "")(implicit ctx: Context): Unit = {
+    printMessage(posStr(pos, kind))
     if (pos.exists) {
-      printSourceLine(pos)
-      printColumnMarker(pos)
-    }
+      val (src, offset) = sourceLine(pos)
+      val marker = columnMarker(pos, offset)
+      val err = errorMsg(pos, msg, offset)
+
+      printMessage(List(src, marker, err).mkString("\n"))
+    } else printMessage(msg)
   }
 
   override def doReport(d: Diagnostic)(implicit ctx: Context): Unit = d match {
     case d: Error =>
-      printMessageAndPos(s"error: ${d.message}", d.pos)
+      printMessageAndPos(d.message, d.pos, "Error in")
       if (ctx.settings.prompt.value) displayPrompt()
     case d: ConditionalWarning if !d.enablingOption.value =>
     case d: MigrationWarning =>
-      printMessageAndPos(s"migration warning: ${d.message}", d.pos)
+      printMessageAndPos(d.message, d.pos, "Migration Warning in")
     case d: Warning =>
-      printMessageAndPos(s"warning: ${d.message}", d.pos)
+      printMessageAndPos(d.message, d.pos, "Warning in")
     case _ =>
       printMessageAndPos(d.message, d.pos)
   }