Router: possibly keep LF before select, and indent

Currently, the code doesn't introduce newlines into select chains even
if their length exceeds the maximum line length.

It also results in missing indent when a comment is in the middle of
such a chain.

Fix both problems, by allowing a newline if one is present in the input.

Fixes scalameta#1334.

scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala

@@ -1340,6 +1340,16 @@ class Router(formatOps: FormatOps) {
           Split(Space, 0, policy = singleLine),
           Split(Newline, 1).withPolicy(penalizeNewlineByNesting(cond, arrow))
         )
+      case FormatToken(_, dot @ T.Dot(), _) =>
+        // allow keeping a newline (and indent) within a select chain
+        val noNewLine = !style.activeForEdition_2019_11 ||
+          newlines == 0 || rightOwner.isNot[Term.Select]
+        val newlinePenalty = if (noNewLine) 0 else 10 + treeDepth(rightOwner)
+        Seq(
+          Split(NoSplit, 0),
+          Split(Newline, newlinePenalty, ignoreIf = noNewLine)
+            .withIndent(2, dot, Left)
+        )
       // Inline comment
       case FormatToken(_, c: T.Comment, between) =>
         Seq(Split(newlines2Modification(between), 0))
@@ -1419,10 +1429,6 @@ class Router(formatOps: FormatOps) {
           Split(NoSplit, 0)
         )
       // Fallback
-      case FormatToken(_, T.Dot(), _) =>
-        Seq(
-          Split(NoSplit, 0)
-        )
       case FormatToken(left, T.Hash(), _) =>
         Seq(
           Split(if (endsWithSymbolIdent(left)) Space else NoSplit, 0)

scalafmt-tests/src/test/resources/default/Select.stat

@@ -62,7 +62,7 @@ val lastToken = owner.body.tokens.filter {
   case _: Whitespace | _: Comment => false
   case _ => true
 } // edge case, if body is empty expire on arrow.
-.lastOption.getOrElse(arrow)
+  .lastOption.getOrElse(arrow)
 <<< apply infix has indent
 val expireAAAAAAAAAAAAAAAAAAAAA = owner.tokens.
   find(t => t.isInstanceOf[`=`] && owners(t) == owner)
@@ -286,7 +286,7 @@ class Foo {
 >>>
 class Foo {
   val vv = v.aaa //
-  .bbb.ccc()
+    .bbb.ccc()
 }
 <<< #1334 continue chain indent after a comment, a bit longer
 class Foo {
@@ -299,9 +299,9 @@ class Foo {
 >>>
 class Foo {
   val vv = v.aaa //
-  .bbb //
-  .ccc //
-  .ddd.eee()
+    .bbb //
+    .ccc //
+    .ddd.eee()
 }
 <<< #1334 continue chain indent after a comment with apply
 class Foo {
@@ -349,6 +349,6 @@ class Foo {
 }
 >>>
 class Foo {
-  val vv =
-    v.aaaaaaaaaa.bbbbbbbbbb.cccccccccc.dddddddddd.eeeeeeeeee.ffffffffff.gggggggggg.hhhhhhhhhh.iiiiiiiiii
+  val vv = v.aaaaaaaaaa.bbbbbbbbbb.cccccccccc.dddddddddd
+    .eeeeeeeeee.ffffffffff.gggggggggg.hhhhhhhhhh.iiiiiiiiii
 }