[PATCH] Preserve hanging indent when breaking line comments.

[Alexander Kornienko]

  Changed getLineCommentIndentPrefix to return a StringRef pointing to the argument.

Hi djasper,

http://llvm-reviews.chandlerc.com/D2988

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D2988?vs=7601&id=7685#toc

Files:
  lib/Format/BreakableToken.cpp
  unittests/Format/FormatTest.cpp

Index: lib/Format/BreakableToken.cpp
===================================================================
--- lib/Format/BreakableToken.cpp
+++ lib/Format/BreakableToken.cpp
@@ -184,19 +184,26 @@
       Prefix, InPPDirective, 1, IndentLevel, LeadingSpaces);
 }
 
-static StringRef getLineCommentPrefix(StringRef Comment) {
-  static const char *const KnownPrefixes[] = { "/// ", "///", "// ", "//" };
-  for (size_t i = 0, e = llvm::array_lengthof(KnownPrefixes); i != e; ++i)
-    if (Comment.startswith(KnownPrefixes[i]))
-      return KnownPrefixes[i];
-  return "";
+static StringRef getLineCommentIndentPrefix(StringRef Comment) {
+  static const char *const KnownPrefixes[] = { "///", "//" };
+  StringRef LongestPrefix;
+  for (StringRef KnownPrefix : KnownPrefixes) {
+    if (Comment.startswith(KnownPrefix)) {
+      size_t PrefixLength = KnownPrefix.size();
+      while (PrefixLength < Comment.size() && Comment[PrefixLength] == ' ')
+        ++PrefixLength;
+      if (PrefixLength > LongestPrefix.size())
+        LongestPrefix = Comment.substr(0, PrefixLength);
+    }
+  }
+  return LongestPrefix;
 }
 
 BreakableLineComment::BreakableLineComment(
     const FormatToken &Token, unsigned IndentLevel, unsigned StartColumn,
     bool InPPDirective, encoding::Encoding Encoding, const FormatStyle &Style)
     : BreakableSingleLineToken(Token, IndentLevel, StartColumn,
-                               getLineCommentPrefix(Token.TokenText), "",
+                               getLineCommentIndentPrefix(Token.TokenText), "",
                                InPPDirective, Encoding, Style) {
   OriginalPrefix = Prefix;
   if (Token.TokenText.size() > Prefix.size() &&
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -1026,6 +1026,21 @@
       format("#define XXX //q w e r t y u i", getLLVMStyleWithColumns(22)));
 }
 
+TEST_F(FormatTest, PreservesHangingIndentInCxxComments) {
+  EXPECT_EQ("//     A comment\n"
+            "//     that doesn't\n"
+            "//     fit on one\n"
+            "//     line",
+            format("//     A comment that doesn't fit on one line",
+                   getLLVMStyleWithColumns(20)));
+  EXPECT_EQ("///     A comment\n"
+            "///     that doesn't\n"
+            "///     fit on one\n"
+            "///     line",
+            format("///     A comment that doesn't fit on one line",
+                   getLLVMStyleWithColumns(20)));
+}
+
 TEST_F(FormatTest, DontSplitLineCommentsWithEscapedNewlines) {
   EXPECT_EQ("// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
             "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
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