[clang-format] Never remove braces in macro definitions

[owenpan]

Summary

Fixes https://github.com/llvm/llvm-project/issues/56559.

[curdeius]

Nice finding! LGTM

clang/lib/Format/UnwrappedLineParser.cpp

case tok::l_brace:
                  /*UnindentWhitesmithsBraces=*/false, CanContainBracedList,
                  NextLBracesType);
       ++StatementCount;
       assert(StatementCount > 0 && "StatementCount overflow!");
       addUnwrappedLine();
       break;
     case tok::r_brace:
       if (OpeningBrace) {
-        if (!Style.RemoveBracesLLVM ||
+        if (!Style.RemoveBracesLLVM || Line->InPPDirective ||
             !OpeningBrace->isOneOf(TT_ControlStatementLBrace, TT_ElseLBrace)) {
           return false;
         }
         if (FormatTok->isNot(tok::r_brace) || StatementCount != 1 || HasLabel ||
             HasDoWhile || IsPrecededByCommentOrPPDirective ||
             precededByCommentOrPPDirective()) {
           return false;
         }

clang/unittests/Format/FormatTest.cpp

verifyFormat("if (condition) {\n"
                "} else {\n"
                "  ff(Indices,\n"
                "     [&](unsigned LHSI, unsigned RHSI) { return true; });\n"
                "}",
                Style);
 
   Style.ColumnLimit = 20;
 
+  verifyFormat("int i;\n"
+               "#define FOO(a, b)  \\\n"
+               "  while (a) {      \\\n"
+               "    b;             \\\n"
+               "  }",
+               Style);
+
   verifyFormat("int ab = [](int i) {\n"
                "  if (i > 0) {\n"
                "    i = 12345678 -\n"
                "        i;\n"
                "  }\n"
                "  return i;\n"
                "};",
                Style);