[clang] [clang-format] Wrap and indent lambda braces in GNU style (PR #135479)

[Owen Pan via cfe-commits]

https://github.com/owenca created https://github.com/llvm/llvm-project/pull/135479

Fix #133135

>From f041f9c3eac94b8f1322ebaa9dfd60d4287840d7 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Fri, 11 Apr 2025 23:36:37 -0700
Subject: [PATCH] [clang-format] Wrap and indent lambda braces in GNU style

Fix #133135
---
 clang/lib/Format/ContinuationIndenter.cpp | 5 +++++
 clang/lib/Format/Format.cpp               | 2 +-
 clang/unittests/Format/FormatTest.cpp     | 9 +++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index 1969f4297b211..9bebac1bed5c6 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -1334,6 +1334,11 @@ unsigned ContinuationIndenter::getNewLineColumn(const LineState &State) {
            Style.IndentWidth;
   }
 
+  if (Style.BraceWrapping.BeforeLambdaBody &&
+      Style.BraceWrapping.IndentBraces && Current.is(TT_LambdaLBrace)) {
+    return CurrentState.Indent + Style.IndentWidth;
+  }
+
   if ((NextNonComment->is(tok::l_brace) && NextNonComment->is(BK_Block)) ||
       (Style.isVerilog() && Keywords.isVerilogBegin(*NextNonComment))) {
     if (Current.NestingLevel == 0 ||
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index b90bd8276e1e2..57175a0be1a6b 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -1435,7 +1435,7 @@ static void expandPresetsBraceWrapping(FormatStyle &Expanded) {
         /*AfterExternBlock=*/true,
         /*BeforeCatch=*/true,
         /*BeforeElse=*/true,
-        /*BeforeLambdaBody=*/false,
+        /*BeforeLambdaBody=*/true,
         /*BeforeWhile=*/true,
         /*IndentBraces=*/true,
         /*SplitEmptyFunction=*/true,
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index f0e67c604cc4b..108d5b90e31f8 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -24268,6 +24268,15 @@ TEST_F(FormatTest, EmptyLinesInLambdas) {
                "};");
 }
 
+TEST_F(FormatTest, LambdaBracesInGNU) {
+  verifyFormat("auto x = [&] ()\n"
+               "  {\n"
+               "    for (int i = 0; i < y; ++i)\n"
+               "      return 97;\n"
+               "  };",
+               getGNUStyle());
+}
+
 TEST_F(FormatTest, FormatsBlocks) {
   FormatStyle ShortBlocks = getLLVMStyle();
   ShortBlocks.AllowShortBlocksOnASingleLine = FormatStyle::SBS_Always;