[clang-format] Add style option PenaltyBreakBeforeMemberAccess (#118409)

The penalty for breaking before a member access is hard-coded to 150.
Add a configuration option to allow setting it.

---------

Co-authored-by: Owen Pan <[email protected]>

Author: gedare

clang/docs/ClangFormatStyleOptions.rst

@@ -5198,6 +5198,11 @@ the configuration (without a prefix: ``Auto``).
 **PenaltyBreakBeforeFirstCallParameter** (``Unsigned``) :versionbadge:`clang-format 3.7` :ref:`¶ <PenaltyBreakBeforeFirstCallParameter>`
   The penalty for breaking a function call after ``call(``.
 
+.. _PenaltyBreakBeforeMemberAccess:
+
+**PenaltyBreakBeforeMemberAccess** (``Unsigned``) :versionbadge:`clang-format 20` :ref:`¶ <PenaltyBreakBeforeMemberAccess>`
+  The penalty for breaking before a member access operator (``.``, ``->``).
+
 .. _PenaltyBreakComment:
 
 **PenaltyBreakComment** (``Unsigned``) :versionbadge:`clang-format 3.7` :ref:`¶ <PenaltyBreakComment>`

clang/docs/ReleaseNotes.rst

@@ -1294,6 +1294,7 @@ clang-format
 - Adds support for bash globstar in ``.clang-format-ignore``.
 - Adds ``WrapNamespaceBodyWithEmptyLines`` option.
 - Adds the ``IndentExportBlock`` option.
+- Adds ``PenaltyBreakBeforeMemberAccess`` option.
 
 libclang
 --------

clang/include/clang/Format/Format.h

@@ -3639,6 +3639,10 @@ struct FormatStyle {
   /// \version 3.7
   unsigned PenaltyBreakBeforeFirstCallParameter;
 
+  /// The penalty for breaking before a member access operator (``.``, ``->``).
+  /// \version 20
+  unsigned PenaltyBreakBeforeMemberAccess;
+
   /// The penalty for each line break introduced inside a comment.
   /// \version 3.7
   unsigned PenaltyBreakComment;
@@ -5311,6 +5315,7 @@ struct FormatStyle {
            PenaltyBreakAssignment == R.PenaltyBreakAssignment &&
            PenaltyBreakBeforeFirstCallParameter ==
                R.PenaltyBreakBeforeFirstCallParameter &&
+           PenaltyBreakBeforeMemberAccess == R.PenaltyBreakBeforeMemberAccess &&
            PenaltyBreakComment == R.PenaltyBreakComment &&
            PenaltyBreakFirstLessLess == R.PenaltyBreakFirstLessLess &&
            PenaltyBreakOpenParenthesis == R.PenaltyBreakOpenParenthesis &&

clang/lib/Format/Format.cpp

@@ -1091,6 +1091,8 @@ template <> struct MappingTraits<FormatStyle> {
     IO.mapOptional("PenaltyBreakAssignment", Style.PenaltyBreakAssignment);
     IO.mapOptional("PenaltyBreakBeforeFirstCallParameter",
                    Style.PenaltyBreakBeforeFirstCallParameter);
+    IO.mapOptional("PenaltyBreakBeforeMemberAccess",
+                   Style.PenaltyBreakBeforeMemberAccess);
     IO.mapOptional("PenaltyBreakComment", Style.PenaltyBreakComment);
     IO.mapOptional("PenaltyBreakFirstLessLess",
                    Style.PenaltyBreakFirstLessLess);
@@ -1659,6 +1661,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
 
   LLVMStyle.PenaltyBreakAssignment = prec::Assignment;
   LLVMStyle.PenaltyBreakBeforeFirstCallParameter = 19;
+  LLVMStyle.PenaltyBreakBeforeMemberAccess = 150;
   LLVMStyle.PenaltyBreakComment = 300;
   LLVMStyle.PenaltyBreakFirstLessLess = 120;
   LLVMStyle.PenaltyBreakOpenParenthesis = 0;

clang/lib/Format/TokenAnnotator.cpp

@@ -4313,9 +4313,11 @@ unsigned TokenAnnotator::splitPenalty(const AnnotatedLine &Line,
     //
     //   aaaaaaa
     //       .aaaaaaaaa.bbbbbbbb(cccccccc);
-    return !Right.NextOperator || !Right.NextOperator->Previous->closesScope()
-               ? 150
-               : 35;
+    const auto *NextOperator = Right.NextOperator;
+    const auto Penalty = Style.PenaltyBreakBeforeMemberAccess;
+    return NextOperator && NextOperator->Previous->closesScope()
+               ? std::min(Penalty, 35u)
+               : Penalty;
   }
 
   if (Right.is(TT_TrailingAnnotation) &&

clang/unittests/Format/ConfigParseTest.cpp

@@ -266,6 +266,8 @@ TEST(ConfigParseTest, ParsesConfiguration) {
   CHECK_PARSE("PenaltyBreakAssignment: 1234", PenaltyBreakAssignment, 1234u);
   CHECK_PARSE("PenaltyBreakBeforeFirstCallParameter: 1234",
               PenaltyBreakBeforeFirstCallParameter, 1234u);
+  CHECK_PARSE("PenaltyBreakBeforeMemberAccess: 1234",
+              PenaltyBreakBeforeMemberAccess, 1234u);
   CHECK_PARSE("PenaltyBreakTemplateDeclaration: 1234",
               PenaltyBreakTemplateDeclaration, 1234u);
   CHECK_PARSE("PenaltyBreakOpenParenthesis: 1234", PenaltyBreakOpenParenthesis,

clang/unittests/Format/FormatTest.cpp

@@ -22365,6 +22365,24 @@ TEST_F(FormatTest, BreakPenaltyAfterForLoopLParen) {
                Style);
 }
 
+TEST_F(FormatTest, BreakPenaltyBeforeMemberAccess) {
+  auto Style = getLLVMStyle();
+  EXPECT_EQ(Style.PenaltyBreakBeforeMemberAccess, 150u);
+
+  Style.ColumnLimit = 60;
+  Style.PenaltyBreakBeforeMemberAccess = 110;
+  verifyFormat("aaaaaaaa.aaaaaaaa.bbbbbbbb()\n"
+               "    .ccccccccccccccccccccc(dddddddd);\n"
+               "aaaaaaaa.aaaaaaaa\n"
+               "    .bbbbbbbb(cccccccccccccccccccccccccccccccc);",
+               Style);
+
+  Style.ColumnLimit = 13;
+  verifyFormat("foo->bar\n"
+               "    .b(a);",
+               Style);
+}
+
 TEST_F(FormatTest, BreakPenaltyScopeResolution) {
   FormatStyle Style = getLLVMStyle();
   Style.ColumnLimit = 20;