SI-7969 REPL -C columnar output

Let `ConsoleReaderHelper.printColumns` print in a vertical
orientation (similar to `ls -C`) instead of horizontally (`ls -x`).

To support the old behavior, add a property `-Dscala.repl.format=across`
where "across" is the presumptive mnemonic for `-x`.

The format property also takes value `paged` to turn on pagination,
which currently forces single-column output (as does `ls | more`)
for simplicity.

4 files changed, 58 insertions, 11 deletions

diff --git a/src/repl/scala/tools/nsc/interpreter/ConsoleReaderHelper.scala b/src/repl/scala/tools/nsc/interpreter/ConsoleReaderHelper.scala
index cf03ecb480..a4315760a2 100644
--- a/src/repl/scala/tools/nsc/interpreter/ConsoleReaderHelper.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ConsoleReaderHelper.scala
@@ -8,7 +8,9 @@ package interpreter
 
 import jline.console.{ ConsoleReader, CursorBuffer }
 
-trait ConsoleReaderHelper extends ConsoleReader {
+trait ConsoleReaderHelper { _: ConsoleReader =>
+  def isAcross: Boolean
+
   def terminal    = getTerminal()
   def width       = terminal.getWidth()
   def height      = terminal.getHeight()
@@ -38,19 +40,42 @@ trait ConsoleReaderHelper extends ConsoleReader {
   }
 
   override def printColumns(items: JCollection[_ <: CharSequence]): Unit =
-    printColumns(items: List[String])
+    printColumns_(items: List[String])
 
-  def printColumns(items: List[String]): Unit = {
-    if (items forall (_ == ""))
-      return
+  private def fits(items: List[String], width: Int): Boolean = (
+    (items map (_.length)).sum + (items.length - 1) * marginSize < width
+  )
+  private def printColumns_(items: List[String]): Unit = if (items exists (_ != "")) {
+    if (fits(items, width)) println(items mkString " " * marginSize)
+    else printMultiLineColumns(items)
+  }
+  private def printMultiLineColumns(items: List[String]): Unit = {
+    import SimpleMath._
+    val longest     = (items map (_.length)).max
+    //val shortest   = (items map (_.length)).min
+    val columnWidth = longest + marginSize
+    val maxcols = {
+      if (isPaginationEnabled) 1
+      else if (columnWidth >= width) 1
+      else 1 max (width / columnWidth)   // make sure it doesn't divide to 0
+    }
+    val nrows       = items.size /% maxcols
+    val ncols       = items.size /% nrows
+    val groupSize   = ncols
+    val padded      = items map (s"%-${columnWidth}s" format _)
+    val xwise       = isAcross || ncols > items.length
+    val grouped: Seq[Seq[String]]    =
+      if (xwise) (padded grouped groupSize).toSeq
+      else {
+        val h       = 1 max padded.size /% groupSize
+        val cols    = (padded grouped h).toList
+        for (i <- 0 until h) yield
+          for (j <- 0 until groupSize) yield
+            if (i < cols(j).size) cols(j)(i) else ""
+      }
 
-    val longest    = items map (_.length) max
     var linesLeft  = if (isPaginationEnabled()) height - 1 else Int.MaxValue
-    val columnSize = longest + marginSize
-    val padded     = items map ("%-" + columnSize + "s" format _)
-    val groupSize  = 1 max (width / columnSize)   // make sure it doesn't divide to 0
-
-    padded grouped groupSize foreach { xs =>
+    grouped foreach { xs =>
       println(xs.mkString)
       linesLeft -= 1
       if (linesLeft <= 0) {
@@ -61,3 +86,10 @@ trait ConsoleReaderHelper extends ConsoleReader {
     }
   }
 }
+
+private[interpreter] object SimpleMath {
+  implicit class DivRem(private val i: Int) extends AnyVal {
+    /** i/n + if (i % n != 0) 1 else 0 */
+    def /%(n: Int): Int = (i + n - 1) / n
+  }
+}
diff --git a/src/repl/scala/tools/nsc/interpreter/JLineReader.scala b/src/repl/scala/tools/nsc/interpreter/JLineReader.scala
index 8b0c6d78fa..970efc1282 100644
--- a/src/repl/scala/tools/nsc/interpreter/JLineReader.scala
+++ b/src/repl/scala/tools/nsc/interpreter/JLineReader.scala
@@ -34,6 +34,10 @@ class JLineReader(_completion: => Completion) extends InteractiveReader {
   }
 
   class JLineConsoleReader extends ConsoleReader with ConsoleReaderHelper {
+    val isAcross = interpreter.`package`.isAcross
+
+    this setPaginationEnabled interpreter.`package`.isPaged
+
     // ASAP
     this setExpandEvents false
 
diff --git a/src/repl/scala/tools/nsc/interpreter/ReplConfig.scala b/src/repl/scala/tools/nsc/interpreter/ReplConfig.scala
index 3392ea0b5e..046d6ecbfb 100644
--- a/src/repl/scala/tools/nsc/interpreter/ReplConfig.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ReplConfig.scala
@@ -46,4 +46,8 @@ trait ReplConfig {
   def isReplDebug: Boolean = replProps.debug || isReplTrace
   def isReplInfo: Boolean  = replProps.info || isReplDebug
   def isReplPower: Boolean = replProps.power
+
+  private def csv(p: String, v: String) = p split "," contains v
+  def isPaged: Boolean     = replProps.format.isSet && csv(replProps.format.get, "paged")
+  def isAcross: Boolean    = replProps.format.isSet && csv(replProps.format.get, "across")
 }
diff --git a/src/repl/scala/tools/nsc/interpreter/ReplProps.scala b/src/repl/scala/tools/nsc/interpreter/ReplProps.scala
index 2364918494..36e6dbbccc 100644
--- a/src/repl/scala/tools/nsc/interpreter/ReplProps.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ReplProps.scala
@@ -18,6 +18,13 @@ class ReplProps {
   val trace = bool("scala.repl.trace")
   val power = bool("scala.repl.power")
 
+  /** CSV of paged,across to enable pagination or `-x` style
+   *  columns, "across" instead of down the column.  Since
+   *  pagination turns off columnar output, these flags are
+   *  currently mutually exclusive.
+   */
+  val format = Prop[String]("scala.repl.format")
+
   val replAutorunCode = Prop[JFile]("scala.repl.autoruncode")
   val powerInitCode   = Prop[JFile]("scala.repl.power.initcode")
   val powerBanner     = Prop[JFile]("scala.repl.power.banner")