[llvm-branch-commits] [clang] release/23.x: [clang-format] Honor new lines before // clang-format on (#218022) (PR #218139)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/218139

Backport 6978738e1efe0c33a9540b70697ce0c83852d9c7

Requested by: @HazardyKnusperkeks

>From 356a3d9fe8d9c73475feaad6bd26c9c480d83a8e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Sch=C3=A4pers?= <bjoern at hazardy.de>
Date: Sat, 22 Aug 2026 13:03:31 +0200
Subject: [PATCH] [clang-format] Honor new lines before // clang-format on
 (#218022)

Fixes #217872.

(cherry picked from commit 6978738e1efe0c33a9540b70697ce0c83852d9c7)
---
 clang/lib/Format/UnwrappedLineFormatter.cpp | 2 ++
 clang/unittests/Format/FormatTest.cpp       | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 7afc7a46dd1c0..b783876b6da8f 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -1637,6 +1637,8 @@ static auto computeNewlines(const AnnotatedLine &Line,
                             const SmallVectorImpl<AnnotatedLine *> &Lines,
                             const FormatStyle &Style) {
   const auto &RootToken = *Line.First;
+  if (isClangFormatOn(RootToken.TokenText))
+    return RootToken.NewlinesBefore;
   auto Newlines =
       std::min(RootToken.NewlinesBefore, Style.MaxEmptyLinesToKeep + 1);
   // Remove empty lines before "}" where applicable.
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 72e0182181763..92bc4c918fb21 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -22420,6 +22420,14 @@ TEST_F(FormatTest, DisableRegions) {
                  " #endif\n"
                  "#endif\n"
                  "// clang-format on");
+
+  verifyNoChange("// clang-format off\n"
+                 "\n"
+                 "\n"
+                 " int  i ;\n"
+                 "\n"
+                 "\n"
+                 "// clang-format on");
 }
 
 TEST_F(FormatTest, OneLineFormatOffRegex) {