[clang-format] Wrap and indent lambda braces in GNU style

Fix #133135

Author: owenca

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 ||

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,

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;