From 21f09aa527eca6ecdfcd38fc7c4e8caaf6fe1388 Mon Sep 17 00:00:00 2001
From: Albert Meltzer <7529386+kitbellew@users.noreply.github.com>
Date: Sun, 26 Dec 2021 01:40:33 -0800
Subject: [PATCH] Router: attach/detach comment to comma as needed

---
 .../scala/org/scalafmt/internal/Router.scala  | 20 ++++++++++---------
 .../src/test/resources/unit/Comment.stat      |  6 ++----
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
index 33f47eacf8..e391699847 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
@@ -1385,18 +1385,20 @@ class Router(formatOps: FormatOps) {
           Split(NoSplit, 0)
         )
       // These are mostly filtered out/modified by policies.
-      case ft @ FormatToken(left: T.Comma, c: T.Comment, _) =>
+      case ft @ FormatToken(lc: T.Comma, c: T.Comment, _) =>
         if (ft.hasBlankLine) Seq(Split(NewlineT(isDouble = true), 0))
         else if (isSingleLineComment(c) || ft.meta.right.hasNL)
           Seq(Split(Space.orNL(newlines), 0))
-        else {
-          val trailingComma =
-            rightIsCloseDelimToAddTrailingComma(left, nextNonComment(next(ft)))
-          Seq(
-            Split(newlines != 0 && !trailingComma, 0)(Space),
-            Split(newlines == 0 && trailingComma, 1)(Newline)
-          )
-        }
+        else if (newlines == 0) {
+          val endFt = nextNonCommentSameLine(next(ft))
+          val useSpaceOnly = endFt.hasBreak ||
+            rightIsCloseDelimToAddTrailingComma(lc, endFt)
+          Seq(Split(Space, 0), Split(useSpaceOnly, 1)(Newline))
+        } else if (
+          !style.comments.willWrap &&
+          rightIsCloseDelimToAddTrailingComma(lc, nextNonComment(next(ft)))
+        ) Seq(Split(Space, 0), Split(Newline, 1))
+        else Seq(Split(Newline, 0))
       case FormatToken(_: T.Comma, right, _) if leftOwner.isNot[Template] =>
         val splitsOpt = argumentStarts.get(hash(right)).flatMap { nextArg =>
           val callSite = isCallSite(leftOwner)
diff --git a/scalafmt-tests/src/test/resources/unit/Comment.stat b/scalafmt-tests/src/test/resources/unit/Comment.stat
index 5a349a781f..00c617da92 100644
--- a/scalafmt-tests/src/test/resources/unit/Comment.stat
+++ b/scalafmt-tests/src/test/resources/unit/Comment.stat
@@ -742,8 +742,7 @@ foo(
 )
 >>>
 foo(
-    barBarBar,
-    /* comment */
+    barBarBar, /* comment */
     qux
 )
 <<< overflow, comma, attached mlc then another arg after space
@@ -755,8 +754,7 @@ foo(
 )
 >>>
 foo(
-    barBarBar,
-    /* comment */
+    barBarBar, /* comment */
     bazBazBaz,
     /* comment */ qux
 )