From 416c5409c26453b31775e4a618de64020694006d Mon Sep 17 00:00:00 2001
From: Albert Meltzer <7529386+kitbellew@users.noreply.github.com>
Date: Wed, 15 May 2024 21:28:31 -0700
Subject: [PATCH] FormatOps: in CtrlBodySplits, add consistency

Previously, the code was computing splits differently for tokens with a
break and without one. Since we could potentially have no-break in the
source but format with one, this could introduce non-idempotency.
---
 .../scala/org/scalafmt/internal/FormatOps.scala   | 15 +++++++--------
 .../src/test/resources/scalajs/DefDef.stat        | 13 ++++++-------
 2 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/FormatOps.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/FormatOps.scala
index 5126c55d16..54be13ab0e 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/FormatOps.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/FormatOps.scala
@@ -1644,21 +1644,20 @@ class FormatOps(
         classicNoBreakFunc: => Split,
     )(nlSplitFunc: Int => Split)(implicit style: ScalafmtConfig): Seq[Split] =
       checkComment(ft, nlSplitFunc) { x =>
+        def getFolded(isKeep: Boolean) =
+          foldedNonComment(body, nlSplitFunc, isKeep = isKeep, spaceIndents)
         style.newlines.getBeforeMultiline match {
+          case Newlines.fold => getFolded(false)
           case Newlines.unfold =>
             unfoldedNonComment(body, nlSplitFunc, spaceIndents, false)
-          case Newlines.classic | Newlines.keep if x.hasBreak =>
-            Seq(nlSplitFunc(0).forThisLine)
-          case Newlines.classic => Option(classicNoBreakFunc).fold {
-              foldedNonComment(body, nlSplitFunc, isKeep = true, spaceIndents)
-            } { func =>
+          case Newlines.classic if x.noBreak =>
+            Option(classicNoBreakFunc).fold(getFolded(true)) { func =>
               val spcSplit = func.forThisLine
               val nlSplit = nlSplitFunc(spcSplit.getCost(_ + 1, 0)).forThisLine
               Seq(spcSplit, nlSplit)
             }
-          case sh => // fold or keep without break
-            val isKeep = sh eq Newlines.keep
-            foldedNonComment(body, nlSplitFunc, isKeep, spaceIndents)
+          case Newlines.keep if x.noBreak => getFolded(true)
+          case _ => getFolded(true).filter(_.isNL) // keep/classic with break
         }
       }
 
diff --git a/scalafmt-tests/src/test/resources/scalajs/DefDef.stat b/scalafmt-tests/src/test/resources/scalajs/DefDef.stat
index 2c08ab02aa..dc321b0273 100644
--- a/scalafmt-tests/src/test/resources/scalajs/DefDef.stat
+++ b/scalafmt-tests/src/test/resources/scalajs/DefDef.stat
@@ -570,10 +570,9 @@ object a {
   }
 }
 >>>
-Idempotency violated
-=> Diff (- obtained, + expected)
-     val registry =
--      new js_FinalizationRegistry[js_Date, String, Any]((heldValue: String) =>
--        ())
-+      new js_FinalizationRegistry[js_Date, String, Any]((heldValue: String) => ())
-   }
+object a {
+  def foo = {
+    val registry =
+      new js_FinalizationRegistry[js_Date, String, Any]((heldValue: String) => ())
+  }
+}