From d6b36350630002c603302efc78bbeb39633ba694 Mon Sep 17 00:00:00 2001
From: Alexander Kornienko <alexfh@google.com>
Date: Mon, 10 Mar 2014 13:14:56 +0000
Subject: [PATCH] Preserve hanging indent when breaking line comments.

Summary:
If we need to break the second line here:
// something: aaaaa aaaaa aaaaaa aaaaa aaaaa
//            aaaaa aaaaa aaaaaa aaaaa aaaaa aaaaa

with the patch it will be turned to

// something: aaaaa aaaaa aaaaaa aaaaa aaaaa
//            aaaaa aaaaa aaaaaa aaaaa aaaaa
//            aaaaa

instead of

// something: aaaaa aaaaa aaaaaa aaaaa aaaaa
//            aaaaa aaaaa aaaaaa aaaaa aaaaa
// aaaaa

Reviewers: djasper, klimek

Reviewed By: klimek

CC: cfe-commits, klimek

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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203458 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Format/BreakableToken.cpp   | 21 ++++++++++++++-------
 unittests/Format/FormatTest.cpp | 15 +++++++++++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/lib/Format/BreakableToken.cpp b/lib/Format/BreakableToken.cpp
index 03693c62bb..d43a774c9c 100644
--- a/lib/Format/BreakableToken.cpp
+++ b/lib/Format/BreakableToken.cpp
@@ -184,19 +184,26 @@ void BreakableStringLiteral::insertBreak(unsigned LineIndex,
       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() &&
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index 6690103dc1..ad1ad04160 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -1026,6 +1026,21 @@ TEST_F(FormatTest, SplitsLongCxxComments) {
       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"
-- 
2.40.0