From 9710e2df7e2674d1554ef59d54c34f6cbdc02605 Mon Sep 17 00:00:00 2001
From: Albert Meltzer <7529386+kitbellew@users.noreply.github.com>
Date: Wed, 15 May 2024 08:48:19 -0700
Subject: [PATCH 1/2] Add non-idempotent binpack.defnsite=oneline test

---
 .../src/test/resources/scalajs/DefDef.stat    | 24 ++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/scalafmt-tests/src/test/resources/scalajs/DefDef.stat b/scalafmt-tests/src/test/resources/scalajs/DefDef.stat
index eca5ac4bd2..5261736e0a 100644
--- a/scalafmt-tests/src/test/resources/scalajs/DefDef.stat
+++ b/scalafmt-tests/src/test/resources/scalajs/DefDef.stat
@@ -541,7 +541,7 @@ newlines.source = keep
 binPack.preset = oneline
 danglingParentheses.preset = false
 newlines.configStyleDefnSite.prefer = true
-# newlines.avoidForSimpleOverflow = [tooLong, punct, slc]
+newlines.avoidForSimpleOverflow = [tooLong, punct, slc]
 ===
 object a {
   def getArrayUnderlyingTypedArrayClassRef(elemTypeRef: NonArrayTypeRef)(implicit tracking: GlobalRefTracking, pos: Position): Option[WithGlobals[VarRef]] = {
@@ -556,3 +556,25 @@ object a {
     // foo
   }
 }
+<<< break at maxColumn, with overflow enabled 3
+preset = default
+maxColumn = 80
+newlines.source = keep
+binPack.preset = oneline
+danglingParentheses.preset = false
+newlines.configStyleDefnSite.prefer = true
+newlines.avoidForSimpleOverflow = [tooLong, punct, slc]
+===
+object a {
+  def foo = {
+    val registry = new js_FinalizationRegistry[js_Date, String, Any]((heldValue: String) => ())
+  }
+}
+>>>
+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) => ())
+   }

From b10c15a6739d4b0f44cabc354440b828252fa97d 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 2/2] 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 5261736e0a..4f26bfb72e 100644
--- a/scalafmt-tests/src/test/resources/scalajs/DefDef.stat
+++ b/scalafmt-tests/src/test/resources/scalajs/DefDef.stat
@@ -571,10 +571,9 @@ 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) => ())
+  }
+}