[clang-format] add BinPackLongBracedLists style option

The use of Cpp11BracedListStyle with BinPackParameters=False
avoids bin packing until reaching a hard-coded limit of 20 items.
This is an arbitrary choice. Introduce a new style option to
allow disabling this limit.

Author: gedare

clang/include/clang/Format/Format.h

@@ -1208,6 +1208,22 @@ struct FormatStyle {
   /// \version 3.7
   bool BinPackArguments;
 
+  /// If ``BinPackLongBracedLists`` is ``true`` it overrides
+  /// ``BinPackArguments`` if there are 20 or more items in a braced
+  /// initializer list.
+  /// \code
+  ///    BinPackLongBracedLists: false  vs.   BinPackLongBracedLists: true
+  ///    vector<int> x{                       vector<int> x{1, 2, ...,
+  ///                                                       20, 21};
+  ///                1,
+  ///                2,
+  ///                ...,
+  ///                20,
+  ///                21};
+  /// \endcode
+  /// \version 20
+  bool BinPackLongBracedLists;
+
   /// Different way to try to fit all parameters on a line.
   enum BinPackParametersStyle : int8_t {
     /// Bin-pack parameters.
@@ -2515,6 +2531,9 @@ struct FormatStyle {
   /// (e.g. a type or variable name), clang-format formats as if the ``{}`` were
   /// the parentheses of a function call with that name. If there is no name,
   /// a zero-length name is assumed.
+  ///
+  /// ``BinPackArguments`` may be forced to true for initializer lists with
+  /// more than 20 items if ``BinPackLongBracedLists`` is true.
   /// \code
   ///    true:                                  false:
   ///    vector<int> x{1, 2, 3, 4};     vs.     vector<int> x{ 1, 2, 3, 4 };
@@ -5172,6 +5191,7 @@ struct FormatStyle {
                R.AlwaysBreakBeforeMultilineStrings &&
            AttributeMacros == R.AttributeMacros &&
            BinPackArguments == R.BinPackArguments &&
+           BinPackLongBracedLists == R.BinPackLongBracedLists &&
            BinPackParameters == R.BinPackParameters &&
            BitFieldColonSpacing == R.BitFieldColonSpacing &&
            BracedInitializerIndentWidth == R.BracedInitializerIndentWidth &&

clang/lib/Format/Format.cpp

@@ -981,6 +981,7 @@ template <> struct MappingTraits<FormatStyle> {
                    Style.AlwaysBreakBeforeMultilineStrings);
     IO.mapOptional("AttributeMacros", Style.AttributeMacros);
     IO.mapOptional("BinPackArguments", Style.BinPackArguments);
+    IO.mapOptional("BinPackLongBracedLists", Style.BinPackLongBracedLists);
     IO.mapOptional("BinPackParameters", Style.BinPackParameters);
     IO.mapOptional("BitFieldColonSpacing", Style.BitFieldColonSpacing);
     IO.mapOptional("BracedInitializerIndentWidth",
@@ -1484,6 +1485,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.AlwaysBreakBeforeMultilineStrings = false;
   LLVMStyle.AttributeMacros.push_back("__capability");
   LLVMStyle.BinPackArguments = true;
+  LLVMStyle.BinPackLongBracedLists = true;
   LLVMStyle.BinPackParameters = FormatStyle::BPPS_BinPack;
   LLVMStyle.BitFieldColonSpacing = FormatStyle::BFCS_Both;
   LLVMStyle.BracedInitializerIndentWidth = std::nullopt;

clang/lib/Format/FormatToken.cpp

@@ -174,7 +174,7 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
   // have many items (20 or more) or we allow bin-packing of function call
   // arguments.
   if (Style.Cpp11BracedListStyle && !Style.BinPackArguments &&
-      Commas.size() < 19) {
+      (Commas.size() < 19 || !Style.BinPackLongBracedLists)) {
     return;
   }
 

clang/unittests/Format/ConfigParseTest.cpp

@@ -160,6 +160,7 @@ TEST(ConfigParseTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL(AllowShortEnumsOnASingleLine);
   CHECK_PARSE_BOOL(AllowShortLoopsOnASingleLine);
   CHECK_PARSE_BOOL(BinPackArguments);
+  CHECK_PARSE_BOOL(BinPackLongBracedLists);
   CHECK_PARSE_BOOL(BreakAdjacentStringLiterals);
   CHECK_PARSE_BOOL(BreakAfterJavaFieldAnnotations);
   CHECK_PARSE_BOOL(BreakBeforeTernaryOperators);

clang/unittests/Format/FormatTest.cpp

@@ -14038,6 +14038,32 @@ TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
       "    ffffff, ggggg,  hhhhhh, iiiiii, jjjjjj, kkkkkk,\n"
       "};",
       NoBinPacking);
+  NoBinPacking.BinPackLongBracedLists = false;
+  verifyFormat("const Aaaaaa aaaaa = {\n"
+               "    aaaaa,\n"
+               "    bbbbb,\n"
+               "    ccccc,\n"
+               "    ddddd,\n"
+               "    eeeee,\n"
+               "    ffffff,\n"
+               "    ggggg,\n"
+               "    hhhhhh,\n"
+               "    iiiiii,\n"
+               "    jjjjjj,\n"
+               "    kkkkkk,\n"
+               "    aaaaa,\n"
+               "    bbbbb,\n"
+               "    ccccc,\n"
+               "    ddddd,\n"
+               "    eeeee,\n"
+               "    ffffff,\n"
+               "    ggggg,\n"
+               "    hhhhhh,\n"
+               "    iiiiii,\n"
+               "    jjjjjj,\n"
+               "    kkkkkk,\n"
+               "};",
+               NoBinPacking);
 
   NoBinPacking.AlignAfterOpenBracket = FormatStyle::BAS_AlwaysBreak;
   verifyFormat("static uint8 CddDp83848Reg[] = {\n"