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

[Owen Pan via cfe-commits]

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

>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 1/2] [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;

>From 5a9aa414c32d2b57e12e2c639e6385275ee91acd Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Sat, 12 Apr 2025 03:51:23 -0700
Subject: [PATCH 2/2] Also handle LBI_OuterScope

---
 clang/lib/Format/ContinuationIndenter.cpp |  8 ++++--
 clang/unittests/Format/FormatTest.cpp     | 32 +++++++++++++++++++----
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index 9bebac1bed5c6..1cf15ea65681d 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -1336,7 +1336,10 @@ unsigned ContinuationIndenter::getNewLineColumn(const LineState &State) {
 
   if (Style.BraceWrapping.BeforeLambdaBody &&
       Style.BraceWrapping.IndentBraces && Current.is(TT_LambdaLBrace)) {
-    return CurrentState.Indent + Style.IndentWidth;
+    const auto From = Style.LambdaBodyIndentation == FormatStyle::LBI_Signature
+                          ? CurrentState.Indent
+                          : State.FirstIndent;
+    return From + Style.IndentWidth;
   }
 
   if ((NextNonComment->is(tok::l_brace) && NextNonComment->is(BK_Block)) ||
@@ -2118,7 +2121,8 @@ void ContinuationIndenter::moveStateToNewBlock(LineState &State, bool NewLine) {
   if (Style.LambdaBodyIndentation == FormatStyle::LBI_OuterScope &&
       State.NextToken->is(TT_LambdaLBrace) &&
       !State.Line->MightBeFunctionDecl) {
-    State.Stack.back().NestedBlockIndent = State.FirstIndent;
+    const auto Indent = Style.IndentWidth * Style.BraceWrapping.IndentBraces;
+    State.Stack.back().NestedBlockIndent = State.FirstIndent + Indent;
   }
   unsigned NestedBlockIndent = State.Stack.back().NestedBlockIndent;
   // ObjC block sometimes follow special indentation rules.
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 108d5b90e31f8..7163a49820ae2 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -24269,12 +24269,34 @@ TEST_F(FormatTest, EmptyLinesInLambdas) {
 }
 
 TEST_F(FormatTest, LambdaBracesInGNU) {
-  verifyFormat("auto x = [&] ()\n"
+  auto Style = getGNUStyle();
+  EXPECT_EQ(Style.LambdaBodyIndentation, FormatStyle::LBI_Signature);
+
+  constexpr StringRef Code("auto x = [&] ()\n"
+                           "  {\n"
+                           "    for (int i = 0; i < y; ++i)\n"
+                           "      return 97;\n"
+                           "  };");
+  verifyFormat(Code, Style);
+
+  Style.LambdaBodyIndentation = FormatStyle::LBI_OuterScope;
+  verifyFormat(Code, Style);
+  verifyFormat("for_each_thread ([] (thread_info *thread)\n"
                "  {\n"
-               "    for (int i = 0; i < y; ++i)\n"
-               "      return 97;\n"
-               "  };",
-               getGNUStyle());
+               "    /* Lambda body.  */\n"
+               "  });",
+               "for_each_thread([](thread_info *thread) {\n"
+               "  /* Lambda body.  */\n"
+               "});",
+               Style);
+  verifyFormat("iterate_over_lwps (scope_ptid, [=] (struct lwp_info *info)\n"
+               "  {\n"
+               "    /* Lambda body.  */\n"
+               "  });",
+               "iterate_over_lwps(scope_ptid, [=](struct lwp_info *info) {\n"
+               "  /* Lambda body.  */\n"
+               "});",
+               Style);
 }
 
 TEST_F(FormatTest, FormatsBlocks) {