clang-format: Allow customizing the penalty for breaking assignment

Summary:
Add option to customize the penalty for breaking assignment

This allows increasing the priority of the assignment, to prefer spliting
an operation instead of splitting the assignment, e.g. :

  int a = bbbbbbbbbbbbbbbb +
          cccccccccccccccc;

Reviewers: krasimir, djasper

Reviewed By: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D32477

llvm-svn: 303534

clang/include/clang/Format/Format.h

@@ -1133,6 +1133,9 @@ struct FormatStyle {
   /// ``Foo <Protocol>`` instead of ``Foo<Protocol>``.
   bool ObjCSpaceBeforeProtocolList;
 
+  /// \brief The penalty for breaking around an assignment operator.
+  unsigned PenaltyBreakAssignment;
+
   /// \brief The penalty for breaking a function call after ``call(``.
   unsigned PenaltyBreakBeforeFirstCallParameter;
 
@@ -1420,6 +1423,8 @@ struct FormatStyle {
            ObjCBlockIndentWidth == R.ObjCBlockIndentWidth &&
            ObjCSpaceAfterProperty == R.ObjCSpaceAfterProperty &&
            ObjCSpaceBeforeProtocolList == R.ObjCSpaceBeforeProtocolList &&
+           PenaltyBreakAssignment ==
+               R.PenaltyBreakAssignment &&
            PenaltyBreakBeforeFirstCallParameter ==
                R.PenaltyBreakBeforeFirstCallParameter &&
            PenaltyBreakComment == R.PenaltyBreakComment &&

clang/lib/Format/Format.cpp

@@ -343,6 +343,8 @@ template <> struct MappingTraits<FormatStyle> {
     IO.mapOptional("ObjCSpaceAfterProperty", Style.ObjCSpaceAfterProperty);
     IO.mapOptional("ObjCSpaceBeforeProtocolList",
                    Style.ObjCSpaceBeforeProtocolList);
+    IO.mapOptional("PenaltyBreakAssignment",
+                   Style.PenaltyBreakAssignment);
     IO.mapOptional("PenaltyBreakBeforeFirstCallParameter",
                    Style.PenaltyBreakBeforeFirstCallParameter);
     IO.mapOptional("PenaltyBreakComment", Style.PenaltyBreakComment);
@@ -582,6 +584,7 @@ FormatStyle getLLVMStyle() {
   LLVMStyle.SpaceBeforeAssignmentOperators = true;
   LLVMStyle.SpacesInAngles = false;
 
+  LLVMStyle.PenaltyBreakAssignment = prec::Assignment;
   LLVMStyle.PenaltyBreakComment = 300;
   LLVMStyle.PenaltyBreakFirstLessLess = 120;
   LLVMStyle.PenaltyBreakString = 1000;

clang/lib/Format/TokenAnnotator.cpp

@@ -2093,9 +2093,10 @@ unsigned TokenAnnotator::splitPenalty(const AnnotatedLine &Line,
   if (Left.is(TT_ConditionalExpr))
     return prec::Conditional;
   prec::Level Level = Left.getPrecedence();
-  if (Level != prec::Unknown)
-    return Level;
+  if (Level == prec::Unknown)
     Level = Right.getPrecedence();
+  if (Level == prec::Assignment)
+    return Style.PenaltyBreakAssignment;
   if (Level != prec::Unknown)
     return Level;
 

clang/unittests/Format/FormatTest.cpp

@@ -3457,6 +3457,18 @@ TEST_F(FormatTest, BreaksAfterAssignments) {
                "    1;");
 }
 
+TEST_F(FormatTest, ConfigurableBreakAssignmentPenalty) {
+  FormatStyle Style = getLLVMStyle();
+  verifyFormat("int aaaaaaaaaaaaaaaaaaaaaaaaaa =\n"
+               "    bbbbbbbbbbbbbbbbbbbbbbbbbb + cccccccccccccccccccccccccc;",
+               Style);
+
+  Style.PenaltyBreakAssignment = 20;
+  verifyFormat("int aaaaaaaaaaaaaaaaaaaaaaaaaa = bbbbbbbbbbbbbbbbbbbbbbbbbb +\n"
+               "                                 cccccccccccccccccccccccccc;",
+               Style);
+}
+
 TEST_F(FormatTest, AlignsAfterAssignments) {
   verifyFormat(
       "int Result = aaaaaaaaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaaaaaaaa +\n"
@@ -8802,6 +8814,8 @@ TEST_F(FormatTest, ParsesConfiguration) {
   CHECK_PARSE("ObjCBlockIndentWidth: 1234", ObjCBlockIndentWidth, 1234u);
   CHECK_PARSE("ColumnLimit: 1234", ColumnLimit, 1234u);
   CHECK_PARSE("MaxEmptyLinesToKeep: 1234", MaxEmptyLinesToKeep, 1234u);
+  CHECK_PARSE("PenaltyBreakAssignment: 1234",
+              PenaltyBreakAssignment, 1234u);
   CHECK_PARSE("PenaltyBreakBeforeFirstCallParameter: 1234",
               PenaltyBreakBeforeFirstCallParameter, 1234u);
   CHECK_PARSE("PenaltyExcessCharacter: 1234", PenaltyExcessCharacter, 1234u);