[clang-format] Add BinPackLongBracedList style option (#112482)

The use of Cpp11BracedListStyle with BinPackArguments=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/docs/ClangFormatStyleOptions.rst

@@ -2182,6 +2182,24 @@ the configuration (without a prefix: ``Auto``).
         aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);
     }
 
+.. _BinPackLongBracedList:
+
+**BinPackLongBracedList** (``Boolean``) :versionbadge:`clang-format 21` :ref:`¶ <BinPackLongBracedList>`
+  If ``BinPackLongBracedList`` is ``true`` it overrides
+  ``BinPackArguments`` if there are 20 or more items in a braced
+  initializer list.
+
+  .. code-block:: c++
+
+     BinPackLongBracedList: false  vs.    BinPackLongBracedList: true
+     vector<int> x{                       vector<int> x{1, 2, ...,
+                                                        20, 21};
+                 1,
+                 2,
+                 ...,
+                 20,
+                 21};
+
 .. _BinPackParameters:
 
 **BinPackParameters** (``BinPackParametersStyle``) :versionbadge:`clang-format 3.7` :ref:`¶ <BinPackParameters>`

clang/docs/ReleaseNotes.rst

@@ -237,6 +237,8 @@ clang-format
 ------------
 
 - Adds ``BreakBeforeTemplateCloser`` option.
+- Adds ``BinPackLongBracedList`` option to override bin packing options in
+  long (20 item or more) braced list initializer lists.
 
 libclang
 --------

clang/include/clang/Format/Format.h

@@ -1212,6 +1212,22 @@ struct FormatStyle {
   /// \version 3.7
   bool BinPackArguments;
 
+  /// If ``BinPackLongBracedList`` is ``true`` it overrides
+  /// ``BinPackArguments`` if there are 20 or more items in a braced
+  /// initializer list.
+  /// \code
+  ///    BinPackLongBracedList: false  vs.    BinPackLongBracedList: true
+  ///    vector<int> x{                       vector<int> x{1, 2, ...,
+  ///                                                       20, 21};
+  ///                1,
+  ///                2,
+  ///                ...,
+  ///                20,
+  ///                21};
+  /// \endcode
+  /// \version 21
+  bool BinPackLongBracedList;
+
   /// Different way to try to fit all parameters on a line.
   enum BinPackParametersStyle : int8_t {
     /// Bin-pack parameters.
@@ -5266,6 +5282,7 @@ struct FormatStyle {
                R.AlwaysBreakBeforeMultilineStrings &&
            AttributeMacros == R.AttributeMacros &&
            BinPackArguments == R.BinPackArguments &&
+           BinPackLongBracedList == R.BinPackLongBracedList &&
            BinPackParameters == R.BinPackParameters &&
            BitFieldColonSpacing == R.BitFieldColonSpacing &&
            BracedInitializerIndentWidth == R.BracedInitializerIndentWidth &&

clang/lib/Format/Format.cpp

@@ -995,6 +995,7 @@ template <> struct MappingTraits<FormatStyle> {
                    Style.AlwaysBreakBeforeMultilineStrings);
     IO.mapOptional("AttributeMacros", Style.AttributeMacros);
     IO.mapOptional("BinPackArguments", Style.BinPackArguments);
+    IO.mapOptional("BinPackLongBracedList", Style.BinPackLongBracedList);
     IO.mapOptional("BinPackParameters", Style.BinPackParameters);
     IO.mapOptional("BitFieldColonSpacing", Style.BitFieldColonSpacing);
     IO.mapOptional("BracedInitializerIndentWidth",
@@ -1507,6 +1508,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.AlwaysBreakBeforeMultilineStrings = false;
   LLVMStyle.AttributeMacros.push_back("__capability");
   LLVMStyle.BinPackArguments = true;
+  LLVMStyle.BinPackLongBracedList = true;
   LLVMStyle.BinPackParameters = FormatStyle::BPPS_BinPack;
   LLVMStyle.BitFieldColonSpacing = FormatStyle::BFCS_Both;
   LLVMStyle.BracedInitializerIndentWidth = std::nullopt;

clang/lib/Format/FormatToken.cpp

@@ -175,7 +175,7 @@ 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.BinPackLongBracedList)) {
     return;
   }
 

clang/unittests/Format/ConfigParseTest.cpp

@@ -168,6 +168,7 @@ TEST(ConfigParseTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL(AllowShortLoopsOnASingleLine);
   CHECK_PARSE_BOOL(AllowShortNamespacesOnASingleLine);
   CHECK_PARSE_BOOL(BinPackArguments);
+  CHECK_PARSE_BOOL(BinPackLongBracedList);
   CHECK_PARSE_BOOL(BreakAdjacentStringLiterals);
   CHECK_PARSE_BOOL(BreakAfterJavaFieldAnnotations);
   CHECK_PARSE_BOOL(BreakBeforeTemplateCloser);

clang/unittests/Format/FormatTest.cpp

@@ -14420,6 +14420,51 @@ TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
       "};",
       NoBinPacking);
 
+  NoBinPacking.BinPackLongBracedList = false;
+  verifyFormat("const Aaaaaa aaaaa = {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};",
+               NoBinPacking);
+  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"
+               "};",
+               NoBinPacking);
+
   NoBinPacking.AlignAfterOpenBracket = FormatStyle::BAS_AlwaysBreak;
   verifyFormat("static uint8 CddDp83848Reg[] = {\n"
                "    CDDDP83848_BMCR_REGISTER,\n"