SI-7969 REPL variable columnar output

Extend column formatting to make columns only as wide as
their widest element.  This is similar to what `ls` does.

Given the longest and shortest string, which bound the
min and max column count, compute the layout for those
possible column counts, and choose the minimal row count
and minimal column count.

The junit test is under pending because it uses expecty.
(Edit: updated without expectytations.)

Example that really benefits, witness the skinny columns:

```
scala> math.

BigDecimal                     PartiallyOrdered             cosh      rint
BigInt                         Pi                           exp       round
E                              ScalaNumber                  expm1     signum
Equiv                          ScalaNumericAnyConversions   floor     sin
Fractional                     ScalaNumericConversions      hypot     sinh
IEEEremainder                  abs                          log       sqrt
Integral                       acos                         log10     tan
LowPriorityEquiv               asin                         log1p     tanh
LowPriorityOrderingImplicits   atan                         max       toDegrees
Numeric                        atan2                        min       toRadians
Ordered                        cbrt                         package   ulp
Ordering                       ceil                         pow
PartialOrdering                cos                          random

```

more

1 files changed, 44 insertions, 0 deletions

diff --git a/test/junit/scala/tools/nsc/interpreter/TabulatorTest.scala b/test/junit/scala/tools/nsc/interpreter/TabulatorTest.scala
index e252942f89..21e338eac0 100644
--- a/test/junit/scala/tools/nsc/interpreter/TabulatorTest.scala
+++ b/test/junit/scala/tools/nsc/interpreter/TabulatorTest.scala
@@ -7,6 +7,7 @@ import org.junit.runner.RunWith
 import org.junit.runners.JUnit4
 
 case class Tabby(width: Int = 80, isAcross: Boolean = false, marginSize: Int = 3) extends Tabulator
+case class VTabby(width: Int = 80, isAcross: Boolean = false, marginSize: Int = 3) extends VariColumnTabulator
 
 @RunWith(classOf[JUnit4])
 class TabulatorTest {
@@ -38,4 +39,47 @@ class TabulatorTest {
     assert(res(1).size == 1)          // no trailing empty strings
     assert(res(1)(0) startsWith "c")
   }
+  // before, two 9-width cols don't fit in 20
+  // but now, 5-col and 9-col do fit.
+  @Test def twolinerVariable() = {
+    val sut   = VTabby(width = 20)
+    val items = (1 to 9) map (i => i.toString * i)
+    val rows  = sut tabulate items
+    assert(rows.size == 5)
+    assert(rows(0).size == 2)
+    assert(rows(0)(0).size == 8) // width is 55555 plus margin of 3
+  }
+  @Test def sys() = {
+    val sut   = VTabby(width = 40)
+    val items = List("BooleanProp", "PropImpl", "addShutdownHook", "error",
+                    "process", "CreatorImpl", "ShutdownHookThread", "allThreads",
+                    "exit", "props", "Prop", "SystemProperties",
+                    "env", "package", "runtime")
+    val rows  = sut tabulate items
+    assert(rows.size == 8)
+    assert(rows(0).size == 2)
+    assert(rows(0)(0).size == "ShutdownHookThread".length + sut.marginSize)   // 21
+  }
+  @Test def syswide() = {
+    val sut   = VTabby(width = 120)
+    val items = List("BooleanProp", "PropImpl", "addShutdownHook", "error",
+                    "process", "CreatorImpl", "ShutdownHookThread", "allThreads",
+                    "exit", "props", "Prop", "SystemProperties",
+                    "env", "package", "runtime")
+    val rows  = sut tabulate items
+    assert(rows.size == 2)
+    assert(rows(0).size == 8)
+    assert(rows(0)(0).size == "BooleanProp".length + sut.marginSize)  // 14
+  }
+  @Test def resultFits() = {
+    val sut   = VTabby(width = 10)
+    // each of two lines would fit, but layout is two cols of width six > 10
+    // therefore, should choose ncols = 1
+    val items = List("a", "bcd",
+                    "efg", "h")
+    val rows  = sut tabulate items
+    assert(rows.size == 4)
+    assert(rows(0).size == 1)
+    assert(rows(0)(0).size == "efg".length + sut.marginSize)  // 6
+  }
 }