[clang-format] Fix bug in block comment reflow that joins * and /

Fixes PR41213

Differential Revision: https://reviews.llvm.org/D61276

llvm-svn: 359943

clang/lib/Format/BreakableToken.cpp

@@ -65,7 +65,8 @@ static StringRef getLineCommentIndentPrefix(StringRef Comment,
 static BreakableToken::Split
 getCommentSplit(StringRef Text, unsigned ContentStartColumn,
                 unsigned ColumnLimit, unsigned TabWidth,
-                encoding::Encoding Encoding, const FormatStyle &Style) {
+                encoding::Encoding Encoding, const FormatStyle &Style,
+                bool DecorationEndsWithStar = false) {
   LLVM_DEBUG(llvm::dbgs() << "Comment split: \"" << Text
                           << "\", Column limit: " << ColumnLimit
                           << ", Content start: " << ContentStartColumn << "\n");
@@ -123,7 +124,10 @@ getCommentSplit(StringRef Text, unsigned ContentStartColumn,
     if (SpaceOffset == 1 && Text[SpaceOffset - 1] == '*')
       return BreakableToken::Split(StringRef::npos, 0);
     StringRef BeforeCut = Text.substr(0, SpaceOffset).rtrim(Blanks);
-    StringRef AfterCut = Text.substr(SpaceOffset).ltrim(Blanks);
+    StringRef AfterCut = Text.substr(SpaceOffset);
+    // Don't trim the leading blanks if it would create a */ after the break.
+    if (!DecorationEndsWithStar || AfterCut.size() <= 1 || AfterCut[1] != '/')
+      AfterCut = AfterCut.ltrim(Blanks);
     return BreakableToken::Split(BeforeCut.size(),
                                  AfterCut.begin() - BeforeCut.end());
   }
@@ -452,6 +456,18 @@ BreakableBlockComment::BreakableBlockComment(
   });
 }
 
+BreakableToken::Split
+BreakableBlockComment::getSplit(unsigned LineIndex, unsigned TailOffset,
+                           unsigned ColumnLimit, unsigned ContentStartColumn,
+                           llvm::Regex &CommentPragmasRegex) const {
+  // Don't break lines matching the comment pragmas regex.
+  if (CommentPragmasRegex.match(Content[LineIndex]))
+    return Split(StringRef::npos, 0);
+  return getCommentSplit(Content[LineIndex].substr(TailOffset),
+                         ContentStartColumn, ColumnLimit, Style.TabWidth,
+                         Encoding, Style, Decoration.endswith("*"));
+}
+
 void BreakableBlockComment::adjustWhitespace(unsigned LineIndex,
                                              int IndentDelta) {
   // When in a preprocessor directive, the trailing backslash in a block comment

clang/lib/Format/BreakableToken.h

@@ -361,6 +361,9 @@ public:
                         bool InPPDirective, encoding::Encoding Encoding,
                         const FormatStyle &Style, bool UseCRLF);
 
+  Split getSplit(unsigned LineIndex, unsigned TailOffset, unsigned ColumnLimit,
+                 unsigned ContentStartColumn,
+                 llvm::Regex &CommentPragmasRegex) const override;
   unsigned getRangeLength(unsigned LineIndex, unsigned Offset,
                           StringRef::size_type Length,
                           unsigned StartColumn) const override;

clang/unittests/Format/FormatTest.cpp

@@ -11150,6 +11150,24 @@ TEST_F(FormatTest, OptimizeBreakPenaltyVsExcess) {
   FormatStyle Style = getLLVMStyle();
   Style.ColumnLimit = 20;
 
+  // See PR41213
+  EXPECT_EQ("/*\n"
+            " *\t9012345\n"
+            " * /8901\n"
+            " */",
+            format("/*\n"
+                   " *\t9012345 /8901\n"
+                   " */",
+                   Style));
+  EXPECT_EQ("/*\n"
+            " *345678\n"
+            " *\t/8901\n"
+            " */",
+            format("/*\n"
+                   " *345678\t/8901\n"
+                   " */",
+                   Style));
+
   verifyFormat("int a; // the\n"
                "       // comment", Style);
   EXPECT_EQ("int a; /* first line\n"