Avoid empty lines in the beginning and end of blocks

docs/configuration.md

@@ -82,6 +82,28 @@ val example2 =
   |""".stripMargin
 ```
 
+## Edition
+
+The `edition` setting allows Scalafmt users to stay on older default settings
+while upgrading to the latest Scalafmt release.
+
+The use-case for configuring the `edition` setting is when you want to upgrade
+to the latest Scalafmt version (for example, to enjoy a bug fix in the parser)
+but need more time to deal with the latest changes in the formatting output.
+
+The end goal for users should be to remove the `edition` setting from
+`.scalafmt.conf` in order to enjoy the latest improvements to the formatting
+output.
+
+```scala mdoc:defaults
+edition
+```
+
+The `edition` setting is formatted as `"$year-$month"` and should be interpreted
+as: "use the default settings at that given date". For example the setting
+`edition = 2019-10` means that the default settings from October 2019 should be
+used.
+
 ## Indentation
 
 ### `continuationIndent.callSite`
@@ -138,9 +160,9 @@ x match { // false for case arrows
 ```
 
 > **Pro tip**: Enable this setting to minimize git diffs/conflicts from
-> renamings and other refactorings, without having to ignore whitespace
-> changes in diffs or use `--ignore-all-space` to avoid conflicts when
-> git merging or rebasing.
+> renamings and other refactorings, without having to ignore whitespace changes
+> in diffs or use `--ignore-all-space` to avoid conflicts when git merging or
+> rebasing.
 
 #### `align=some`
 

scalafmt-core/shared/src/main/scala/org/scalafmt/config/Edition.scala

@@ -0,0 +1,24 @@
+package org.scalafmt.config
+
+import metaconfig.{Conf, ConfDecoder, ConfEncoder, Configured}
+
+case class Edition(year: Int, month: Int)
+
+object Edition {
+  val Latest = Edition(Int.MaxValue, Int.MaxValue)
+  implicit val ordering: Ordering[Edition] =
+    Ordering.by[Edition, (Int, Int)](e => e.year -> e.month)
+  lazy val format = "(\\d{4})-(\\d{1,2})".r
+
+  implicit val decoder: ConfDecoder[Edition] =
+    ConfDecoder.instanceExpect("'$year-$month', for example '2019-08'") {
+      case Conf.Str(format(year, month)) =>
+        Configured.ok(Edition(year.toInt, month.toInt))
+      case Conf.Str("latest") => Configured.ok(Latest)
+    }
+
+  implicit val encoder: ConfEncoder[Edition] =
+    ConfEncoder.instance(
+      edition => Conf.Str(f"${edition.year}%d-${edition.month}%02d")
+    )
+}

scalafmt-core/shared/src/main/scala/org/scalafmt/config/Newlines.scala

@@ -110,7 +110,8 @@ case class Newlines(
     beforeImplicitKWInVerticalMultiline: Boolean = false,
     alwaysBeforeElseAfterCurlyIf: Boolean = false,
     alwaysBeforeMultilineDef: Boolean = true,
-    avoidAfterYield: Boolean = true
+    avoidAfterYield: Boolean = true,
+    avoidEmptyLinesAroundBlock: Option[Boolean] = None
 ) {
   val reader: ConfDecoder[Newlines] = generic.deriveDecoder(this).noTypos
 }

scalafmt-core/shared/src/main/scala/org/scalafmt/config/ScalafmtConfig.scala

@@ -9,6 +9,8 @@ import metaconfig.Configured._
 import org.scalafmt.util.LoggerOps
 import org.scalafmt.util.ValidationOps
 
+import Edition.ordering._
+
 /** Configuration options for scalafmt.
   *
   * @param version The version of scalafmt to use for this project. Currently not used,
@@ -159,7 +161,8 @@ case class ScalafmtConfig(
     verticalAlignMultilineOperators: Boolean = false,
     onTestFailure: String = "",
     encoding: Codec = "UTF-8",
-    project: ProjectFiles = ProjectFiles()
+    project: ProjectFiles = ProjectFiles(),
+    edition: Edition = Edition.Latest
 ) {
   private implicit val runnerReader = runner.reader
   private implicit val projectReader = project.reader
@@ -189,6 +192,9 @@ case class ScalafmtConfig(
     continuationIndent.callSite,
     continuationIndent.defnSite
   )
+
+  val avoidEmptyLinesAroundBlock: Boolean =
+    newlines.avoidEmptyLinesAroundBlock.getOrElse(edition > Edition(2019, 10))
 }
 
 object ScalafmtConfig {

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

@@ -184,6 +184,7 @@ class Router(formatOps: FormatOps) {
             selfAnnotation.nonEmpty
         val nl: Modification =
           if (isSelfAnnotation) newlines2Modification(formatToken)
+          else if (style.avoidEmptyLinesAroundBlock) NewlineT()
           else NewlineT(shouldGet2xNewlines(tok, style, owners))
 
         val (startsLambda, lambdaPolicy, lambdaArrow, lambdaIndent) =
@@ -347,6 +348,11 @@ class Router(formatOps: FormatOps) {
           )
         }
 
+      case FormatToken(_, T.RightBrace(), _)
+          if style.avoidEmptyLinesAroundBlock && newlines > 1 =>
+        Seq(
+          Split(NoSplit, 0)
+        )
       case FormatToken(_, T.RightBrace(), _) =>
         Seq(
           Split(xmlSpace(rightOwner), 0),

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

@@ -223,7 +223,6 @@ callStatement = js.If(genIsInstanceOf(callTrg, rtClass.tpe), {
         rawApply
     } else {
       val reflBoxClassPatched = {
-
         def isIntOrLongKind(kind: TypeKind) = kind match {
           case _: INT | LONG => true
           case _ => false

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

@@ -249,7 +249,6 @@ class ResolutionCopier(x: Int) {
 }
 >>>
 class ResolutionCopier(x: Int) {
-
   def visitClassDeclaration(node: ClassDeclaration): Boolean = {
     val toNode = this._toNode.asInstanceOf[ClassDeclaration];
     javaBooleanAnd(

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

@@ -62,7 +62,6 @@ class MediaStream() extends EventTarget {
 }
 >>>
 class MediaStream() extends EventTarget {
-
   /**
     */
   val ended: Boolean = js.native

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

@@ -10,7 +10,6 @@
   }
 >>>
 {
-
   def cancel(reason: Any): js.Promise[Any] = js.native // comment
 
   /**
@@ -29,7 +28,6 @@ object KeyValue {
 }
 >>>
 object KeyValue {
-
   // ================================
   // 6.3.1 Special Key Values
 
@@ -45,7 +43,6 @@ object KeyValue {
 }
 >>>
 object KeyValue {
-
   // comment
   /** This key value */
   final val Unidentified = "Unidentified"
@@ -74,7 +71,6 @@ object D {
   }
 >>>
 object D {
-
   private val decompressedPrefixes: Seq[(String, String)] =
     compressedPrefixes map { case (a, b) => (b, a) }
 
@@ -94,7 +90,6 @@ object Primes {
 }
 >>>
 object Primes {
-
   // prime sieve; use instead of the test or stream when you know the
   // upper bound of the primes you will need.
   // en.wikipedia.org/wiki/Sieve_of_Eratosthenes

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

@@ -9,7 +9,6 @@ object a {
 }
 >>>
 object a {
-
   /**
     * Returns True is this state will always return better formatting than other.
     */

scalafmt-tests/src/test/resources/default/Fidelity.source

@@ -10,7 +10,6 @@ object ScalaJSGroupID {
 }
 >>>
 object ScalaJSGroupID {
-
   def auto_impl(c: Context { type PrefixType = ScalaJSGroupID })()
       : Expr[CrossGroupArtifactID] = {
     reify {}

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

@@ -86,7 +86,6 @@ val bindingFuture = Http().bindAndHandleSync({
 >>>
 {
   {
-
     {
       {
         {
@@ -103,7 +102,6 @@ val bindingFuture = Http().bindAndHandleSync({
       }
     }
   }
-
 }
 <<< rendering #339
 {{
@@ -130,7 +128,6 @@ val bindingFuture = Http().bindAndHandleSync({
           RequestRenderingContext(request, hostHeader, sendEntityTrigger)
         }
       }
-
     })
   }
 }
@@ -169,7 +166,6 @@ val bindingFuture = Http().bindAndHandleSync({
                                  })
         new ResponseParsingMerge(rootParser)
       }
-
     })
   }
 }

scalafmt-tests/src/test/resources/newlines/alwaysBeforeTopLevelStatements.stat

@@ -132,7 +132,6 @@ object A {
 }
 >>>
 object A {
-
   /** test */
   def foo(): Int = 0
   // bar

scalafmt-tests/src/test/resources/newlines/avoidEmptyLinesAroundBlock.stat

@@ -0,0 +1,55 @@
+maxColumn = 80
+newlines.avoidEmptyLinesAroundBlock = true
+
+<<< should remove empty lines at the beginning of a def block
+def other: String = {
+
+  "Result"
+}
+>>>
+def other: String = {
+  "Result"
+}
+
+<<< should remove empty lines at the beginning and end of a def block
+def other: String = {
+
+  "Result"
+
+}
+>>>
+def other: String = {
+  "Result"
+}
+
+<<< should remove empty lines at the beginning and end of a val block
+def other: String = {
+
+  val aux = {
+
+    "Result"
+
+  }
+
+  aux
+
+}
+>>>
+def other: String = {
+  val aux = {
+    "Result"
+  }
+
+  aux
+}
+
+<<< should remove empty lines at the end of a block
+def other: String = {
+  "Result"
+
+
+}
+>>>
+def other: String = {
+  "Result"
+}

scalafmt-tests/src/test/resources/rewrite/RedundantBraces-case.stat

@@ -15,14 +15,12 @@ object a {
 }
 >>>
 object a {
-
   val x: Int => String = {
     case 2 =>
       "two"
     case _ =>
       "other"
   }
-
 }
 <<< case clauses with stuff
 object a {
@@ -41,7 +39,6 @@ object a {
 }
 >>>
 object a {
-
   val x: Int => String = {
     case 2 =>
       println("TWO")
@@ -50,7 +47,6 @@ object a {
       // Nice
       "other"
   }
-
 }
 <<< case clauses to unit
 object a {
@@ -66,12 +62,10 @@ object a {
 }
 >>>
 object a {
-
   val x: Int => Unit = {
     case 0 =>
     case 1 =>
     case 2 =>
     case _ => println("?")
   }
-
 }

scalafmt-tests/src/test/resources/rewrite/RedundantBraces-if.stat

@@ -15,15 +15,13 @@ object a {
 }
 >>>
 object a {
-
   def x(i: Int): String =
     if (i == 0)
       "zero"
     else if (i < 0)
       "sub-zero"
     else
       "other"
-
 }
 <<< if-else with stuff
 object a {
@@ -50,7 +48,6 @@ object a {
 }
 >>>
 object a {
-
   def x(i: Int): String =
     if (i == 0)
       /* what */
@@ -88,7 +85,6 @@ object a {
 }
 >>>
 object a {
-
   val x: Int => Unit =
     if (i == 0)
       println("zero")
@@ -98,7 +94,6 @@ object a {
   def y(i: Int) =
     if (i > 0)
       println("yes!")
-
 }
 <<< nested if
 object a {