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

Fix #133135

Author: owenca

clang/lib/Format/ContinuationIndenter.cpp

@@ -1334,6 +1334,14 @@ unsigned ContinuationIndenter::getNewLineColumn(const LineState &State) {
            Style.IndentWidth;
   }
 
+  if (Style.BraceWrapping.BeforeLambdaBody &&
+      Style.BraceWrapping.IndentBraces && Current.is(TT_LambdaLBrace)) {
+    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)) ||
       (Style.isVerilog() && Keywords.isVerilogBegin(*NextNonComment))) {
     if (Current.NestingLevel == 0 ||
@@ -2113,7 +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.

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

@@ -24267,6 +24267,37 @@ TEST_F(FormatTest, EmptyLinesInLambdas) {
                "};");
 }
 
+TEST_F(FormatTest, LambdaBracesInGNU) {
+  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"
+               "    /* 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) {
   FormatStyle ShortBlocks = getLLVMStyle();
   ShortBlocks.AllowShortBlocksOnASingleLine = FormatStyle::SBS_Always;