[clang-format [PR45791] BeforeLambdaBody is confused by comment inside lambda

[MyDeveloperDay]

Summary

https://bugs.llvm.org/show_bug.cgi?id=45791

Lambda with line comment is incorrectly formatted

auto k = []() // comment
{ return; };
`

auto k = []() // comment { return; };

[Wawha]

Thanks for the patch !

clang/lib/Format/ContinuationIndenter.cpp

bool ContinuationIndenter::canBreak(const LineState &State) {
 
   return !State.Stack.back().NoLineBreak;
 }
 
 bool ContinuationIndenter::mustBreak(const LineState &State) {
   const FormatToken &Current = *State.NextToken;
   const FormatToken &Previous = *Current.Previous;
   if (Style.BraceWrapping.BeforeLambdaBody && Current.CanBreakBefore &&
-      Current.is(TT_LambdaLBrace)) {
+      Current.is(TT_LambdaLBrace) && Previous.isNot(TT_LineComment)) {
     auto LambdaBodyLength = getLengthToMatchingParen(Current, State.Stack);
     return (LambdaBodyLength > getColumnLimit(State));
   }
   if (Current.MustBreakBefore || Current.is(TT_InlineASMColon))
     return true;
   if (State.Stack.back().BreakBeforeClosingBrace &&
       Current.closesBlockOrBlockTypeList(Style))
     return true;

clang/unittests/Format/FormatTest.cpp

verifyFormat("TwoNestedLambdas_SLS_All(\n"
                "          {\n"
                "            // A cool function...\n"
                "            return 17;\n"
                "          });\n"
                "    });",
                LLVMWithBeforeLambdaBody);
 }
 
+TEST_F(FormatTest, LambdaWithLineComments) {
+  FormatStyle LLVMWithBeforeLambdaBody = getLLVMStyle();
+  LLVMWithBeforeLambdaBody.BreakBeforeBraces = FormatStyle::BS_Custom;
+  LLVMWithBeforeLambdaBody.BraceWrapping.BeforeLambdaBody = true;
+  LLVMWithBeforeLambdaBody.AllowShortLambdasOnASingleLine =
+      FormatStyle::ShortLambdaStyle::SLS_All;
+
+  verifyFormat("auto k = []() { return; }", LLVMWithBeforeLambdaBody);
+  verifyFormat("auto k = []() // comment\n"
+               "{ return; }",
+               LLVMWithBeforeLambdaBody);
+  verifyFormat("auto k = []() /* comment */ { return; }",
+               LLVMWithBeforeLambdaBody);
+  verifyFormat("auto k = []() /* comment */ /* comment */ { return; }",
+               LLVMWithBeforeLambdaBody);
+  verifyFormat("auto k = []() // X\n"
+               "{ return; }",
+               LLVMWithBeforeLambdaBody);
+  verifyFormat(
+      "auto k = []() // XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\n"
+      "{ return; }",
+      LLVMWithBeforeLambdaBody);
+}
+
 TEST_F(FormatTest, EmptyLinesInLambdas) {
   verifyFormat("auto lambda = []() {\n"
                "  x(); //\n"
                "};",
                "auto lambda = []() {\n"
                "\n"
                "  x(); //\n"
                "\n"