Splits: ensure break between yield and case

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

@@ -3377,25 +3377,31 @@ object SplitsAfterYield extends Splits {
       cfg: ScalafmtConfig,
   ): Seq[Split] = {
     import fo._, tokens._, ft._
-    leftOwner match {
-      case t: Term.ForYield =>
-        val lastToken = getLast(t.body)
-        if (
-          t.body.is[Tree.Block] && right.is[T.LeftBrace] &&
-          matchingOptRight(ft).exists(_.idx >= lastToken.idx)
-        ) Seq(Split(Space, 0))
-        else {
-          val indent = Indent(cfg.indent.main, lastToken, ExpiresOn.After)
-          if (cfg.newlines.avoidAfterYield && !rightOwner.is[Term.If]) {
-            val noIndent = !isRightCommentWithBreak(ft)
-            Seq(Split(Space, 0).withIndent(indent, noIndent))
-          } else Seq(
-            // Either everything fits in one line or break on =>
-            Split(Space, 0).withSingleLine(lastToken),
-            Split(Newline, 1).withIndent(indent),
-          )
-        }
-      case _ => Seq.empty
+    (leftOwner match {
+      case t: Term.ForYield => Some(t.body)
+      case _ => None
+    }).fold(Seq.empty[Split]) {
+      case b: Term.PartialFunction
+          if dialect.allowSignificantIndentation &&
+            nextNonComment(ft).right.is[T.KwCase] =>
+        val split = Split(Newline, 0)
+          .withIndent(cfg.indent.getSignificant, getLast(b), ExpiresOn.After)
+        Seq(split)
+      case b: Tree.Block
+          if right.is[T.LeftBrace] &&
+            matchingOptRight(ft).exists(_.idx >= getLast(b).idx) =>
+        Seq(Split(Space, 0))
+      case b =>
+        val lastToken = getLast(b)
+        val indent = Indent(cfg.indent.main, lastToken, ExpiresOn.After)
+        if (cfg.newlines.avoidAfterYield && !rightOwner.is[Term.If]) {
+          val noIndent = !isRightCommentWithBreak(ft)
+          Seq(Split(Space, 0).withIndent(indent, noIndent))
+        } else Seq(
+          // Either everything fits in one line or break on =>
+          Split(Space, 0).withSingleLine(lastToken),
+          Split(Newline, 1).withIndent(indent),
+        )
     }
   }
 }

scalafmt-tests/shared/src/test/resources/scala3/OptionalBraces.stat

@@ -8527,3 +8527,12 @@ object a {
     x = "string"
   )
 }
+<<< #4857
+for
+  foo <- Some(42)
+yield
+  case Some(x) => foo
+>>>
+for foo <- Some(42)
+yield
+   case Some(x) => foo

scalafmt-tests/shared/src/test/resources/scala3/OptionalBraces_fold.stat

@@ -8190,3 +8190,12 @@ object a {
     x = "string"
   )
 }
+<<< #4857
+for
+  foo <- Some(42)
+yield
+  case Some(x) => foo
+>>>
+for foo <- Some(42)
+yield
+   case Some(x) => foo

scalafmt-tests/shared/src/test/resources/scala3/OptionalBraces_keep.stat

@@ -8549,3 +8549,13 @@ object a {
     x = "string"
   )
 }
+<<< #4857
+for
+  foo <- Some(42)
+yield
+  case Some(x) => foo
+>>>
+for
+   foo <- Some(42)
+yield
+   case Some(x) => foo

scalafmt-tests/shared/src/test/resources/scala3/OptionalBraces_unfold.stat

@@ -8877,3 +8877,13 @@ object a {
     x = "string"
   )
 }
+<<< #4857
+for
+  foo <- Some(42)
+yield
+  case Some(x) => foo
+>>>
+for foo <- Some(42)
+yield
+   case Some(x) =>
+     foo

scalafmt-tests/shared/src/test/scala/org/scalafmt/FormatTests.scala

@@ -148,7 +148,7 @@ class FormatTests extends FunSuite with CanRunTests with FormatAssertions {
     val explored = Debug.explored.get()
     logger.debug(s"Total explored: $explored")
     if (!onlyUnit && !onlyManual)
-      assertEquals(explored, 2537604, "total explored")
+      assertEquals(explored, 2537916, "total explored")
     // TODO(olafur) don't block printing out test results.
     TestPlatformCompat.executeAndWait(PlatformFileOps.writeFile(
       FileOps.getPath("target", "index.html"),