clang-format: Let a trailing comma in braced lists enforce linebreaks.

Before:
  vector<int> x{1, 2, 3, 4, };

After:
  vector<int> x{
      1, 2, 3, 4,
  };

This fixes llvm.org/PR18519.

llvm-svn: 204458

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index c3cc000044b..efb983e7366 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -1478,6 +1478,7 @@ bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
 
 bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
                                      const FormatToken &Right) {
+  const FormatToken &Left = *Right.Previous;
   if (Right.is(tok::comment)) {
     return Right.Previous->BlockKind != BK_BracedInit &&
            Right.Previous->Type != TT_CtorInitializerColon &&
@@ -1514,6 +1515,13 @@ bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
              Style.Language == FormatStyle::LK_Proto) {
     // Don't enums onto single lines in protocol buffers.
     return true;
+  } else if ((Left.is(tok::l_brace) && Left.MatchingParen &&
+              Left.MatchingParen->Previous &&
+              Left.MatchingParen->Previous->is(tok::comma)) ||
+             (Right.is(tok::r_brace) && Left.is(tok::comma))) {
+    // If the last token before a '}' is a comma, the intention is to insert a
+    // line break after it in order to make shuffling around entries easier.
+    return true;
   }
   return false;
 }