[clang] [clang-format] Skip line splices when sorting C++ includes (PR #120680)

[Owen Pan via cfe-commits]

https://github.com/owenca created https://github.com/llvm/llvm-project/pull/120680

Fixes #109864.

>From cb71ed39160ad46566db7ce5d4ab622ffcf842ee Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Thu, 19 Dec 2024 19:59:23 -0800
Subject: [PATCH] [clang-format] Skip line splices when sorting C++ includes

Fixes #109864.
---
 clang/lib/Format/Format.cpp                 |  9 ++++++++-
 clang/unittests/Format/SortIncludesTest.cpp | 12 ++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index dcaac4b0d42cc5..f79f9cb1ecdd22 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -3247,7 +3247,14 @@ tooling::Replacements sortCppIncludes(const FormatStyle &Style, StringRef Code,
   std::string RawStringTermination = ")\"";
 
   for (;;) {
-    auto Pos = Code.find('\n', SearchFrom);
+    size_t Pos = SearchFrom;
+    if (Code[SearchFrom] != '\n') {
+      do { // Search for the first newline while skipping line splices.
+        ++Pos;
+        Pos = Code.find('\n', Pos);
+      } while (Pos != StringRef::npos && Code[Pos - 1] == '\\');
+    }
+
     StringRef Line =
         Code.substr(Prev, (Pos != StringRef::npos ? Pos : Code.size()) - Prev);
 
diff --git a/clang/unittests/Format/SortIncludesTest.cpp b/clang/unittests/Format/SortIncludesTest.cpp
index 31753825646373..cb3f8c73a04871 100644
--- a/clang/unittests/Format/SortIncludesTest.cpp
+++ b/clang/unittests/Format/SortIncludesTest.cpp
@@ -984,6 +984,18 @@ TEST_F(SortIncludesTest, SortAndDeduplicateIncludes) {
                     "#include <c>\n"
                     "#include <b>"));
 
+  verifyFormat("/* COPYRIGHT *\\\n"
+               "\\* (C) 2024  */\n"
+               "\n"
+               "#include <a>\n"
+               "#include <b>",
+               sort("/* COPYRIGHT *\\\n"
+                    "\\* (C) 2024  */\n"
+                    "\n"
+                    "#include <b>\n"
+                    "#include <a>\n"
+                    "#include <b>"));
+
   Style.IncludeBlocks = tooling::IncludeStyle::IBS_Merge;
   verifyFormat("#include <a>\n"
                "#include <b>\n"