[clang] [clang-format] Handle doxygen commands starting with \ (PR #80381)

[Fernando Tagawa via cfe-commits]

https://github.com/XDeme created https://github.com/llvm/llvm-project/pull/80381

Fixes llvm/llvm-project#63241

Doxygen commands can start with `@` or `\`.

>From efd816282e5f5b71d6f88038a2121fa698becf7a Mon Sep 17 00:00:00 2001
From: XDeme <fernando.tagawa.gamail.com at gmail.com>
Date: Fri, 2 Feb 2024 00:27:57 -0300
Subject: [PATCH] [clang-format] Handle doxygen comments starting with \

---
 clang/lib/Format/BreakableToken.cpp           | 4 ++--
 clang/unittests/Format/FormatTestComments.cpp | 8 ++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Format/BreakableToken.cpp b/clang/lib/Format/BreakableToken.cpp
index 473908e8fee3b..75304908dc650 100644
--- a/clang/lib/Format/BreakableToken.cpp
+++ b/clang/lib/Format/BreakableToken.cpp
@@ -449,11 +449,11 @@ const FormatToken &BreakableComment::tokenAt(unsigned LineIndex) const {
 
 static bool mayReflowContent(StringRef Content) {
   Content = Content.trim(Blanks);
-  // Lines starting with '@' commonly have special meaning.
+  // Lines starting with '@' or '\' commonly have special meaning.
   // Lines starting with '-', '-#', '+' or '*' are bulleted/numbered lists.
   bool hasSpecialMeaningPrefix = false;
   for (StringRef Prefix :
-       {"@", "TODO", "FIXME", "XXX", "-# ", "- ", "+ ", "* "}) {
+       {"@", "\\", "TODO", "FIXME", "XXX", "-# ", "- ", "+ ", "* "}) {
     if (Content.starts_with(Prefix)) {
       hasSpecialMeaningPrefix = true;
       break;
diff --git a/clang/unittests/Format/FormatTestComments.cpp b/clang/unittests/Format/FormatTestComments.cpp
index c249f4d9333fd..0327937e4496a 100644
--- a/clang/unittests/Format/FormatTestComments.cpp
+++ b/clang/unittests/Format/FormatTestComments.cpp
@@ -1909,6 +1909,14 @@ TEST_F(FormatTestComments, ReflowsComments) {
                    "// @param arg",
                    getLLVMStyleWithColumns(20)));
 
+  // Don't reflow lines starting with '\'.
+  EXPECT_EQ("// long long long\n"
+            "// long\n"
+            "// \\param arg",
+            format("// long long long long\n"
+                   "// \\param arg",
+                   getLLVMStyleWithColumns(20)));
+
   // Don't reflow lines starting with 'TODO'.
   EXPECT_EQ("// long long long\n"
             "// long\n"