From 7d23e595d82342685b047ce39f1062e6d8f4a882 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nivaldo=20Bondan=C3=A7a?= <nbondanca@meta.com>
Date: Thu, 6 Jun 2024 21:46:10 -0700
Subject: [PATCH] Preserve new lines between when clauses

Summary:
Implemented as requested on
https://github.com/facebook/ktfmt/issues/342

Reviewed By: davidtorosyan

Differential Revision: D58271914

fbshipit-source-id: 048d9a754b40200f313654775eb743c024073d39
---
 .../ktfmt/format/KotlinInputAstVisitor.kt     |  6 ++-
 .../facebook/ktfmt/format/FormatterTest.kt    | 44 +++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/com/facebook/ktfmt/format/KotlinInputAstVisitor.kt b/core/src/main/java/com/facebook/ktfmt/format/KotlinInputAstVisitor.kt
index 6a620222..608af596 100644
--- a/core/src/main/java/com/facebook/ktfmt/format/KotlinInputAstVisitor.kt
+++ b/core/src/main/java/com/facebook/ktfmt/format/KotlinInputAstVisitor.kt
@@ -1882,8 +1882,12 @@ class KotlinInputAstVisitor(
       builder.space()
       builder.token("{", Doc.Token.RealOrImaginary.REAL, blockIndent, Optional.of(blockIndent))
 
-      expression.entries.forEach { whenEntry ->
+      expression.entries.forEachIndexed { index, whenEntry ->
         builder.block(blockIndent) {
+          if (index != 0) {
+            // preserve new line if there's one
+            builder.blankLineWanted(OpsBuilder.BlankLineWanted.PRESERVE)
+          }
           builder.forcedBreak()
           if (whenEntry.isElse) {
             builder.token("else")
diff --git a/core/src/test/java/com/facebook/ktfmt/format/FormatterTest.kt b/core/src/test/java/com/facebook/ktfmt/format/FormatterTest.kt
index b88138ba..4e8acc27 100644
--- a/core/src/test/java/com/facebook/ktfmt/format/FormatterTest.kt
+++ b/core/src/test/java/com/facebook/ktfmt/format/FormatterTest.kt
@@ -1635,6 +1635,50 @@ class FormatterTest {
       |"""
               .trimMargin())
 
+  @Test
+  fun `newlines between clauses of when() are preserved`() {
+    assertThatFormatting(
+            """
+        |fun f(x: Int) {
+        |  when (x) {
+        |
+        |
+        |    1 -> print(1)
+        |    2 -> print(2)
+        |
+        |
+        |    3 ->
+        |        // Comment
+        |        print(3)
+        |
+        |    else -> {
+        |      print("else")
+        |    }
+        |
+        |  }
+        |}
+        |"""
+                .trimMargin())
+        .isEqualTo(
+            """
+        |fun f(x: Int) {
+        |  when (x) {
+        |    1 -> print(1)
+        |    2 -> print(2)
+        |
+        |    3 ->
+        |        // Comment
+        |        print(3)
+        |
+        |    else -> {
+        |      print("else")
+        |    }
+        |  }
+        |}
+        |"""
+                .trimMargin())
+  }
+
   @Test
   fun `when() with a subject expression`() =
       assertFormatted(