[PATCH] Don't break line comments with escaped newlines.

[Alexander Kornienko]

Hi djasper,

These can appear when comments contain command lines with quoted line
breaks. As the text (including escaped newlines and '//' from consecutive lines)
is a single line comment, we used to break it even when it didn't exceed column
limit. This is a temporary solution, in the future we may want to support this
case completely - at least adjust leading whitespace when changing indentation
of the first line.

http://llvm-reviews.chandlerc.com/D1146

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

Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -914,6 +914,16 @@
     } else if (Current.Type == TT_LineComment &&
                (Current.Previous == NULL ||
                 Current.Previous->Type != TT_ImplicitStringLiteral)) {
+      // Don't break line comments with escaped newlines. These look like
+      // separate line comments, but in fact contain consecutive lines including
+      // leading whitespace and '//' markers.
+      //
+      // TODO: If we want to handle them correctly, we'll need to adjust leading
+      // whitespace in consecutive lines when changing indentation of the first
+      // line similar to what we do with block comments.
+      if (Current.TokenText.find("\\\n") != StringRef::npos)
+        return 0;
+
       Token.reset(new BreakableLineComment(Current, StartColumn,
                                            Line.InPPDirective, Encoding));
     } else {
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -921,6 +921,15 @@
                    getLLVMStyleWithColumns(20)));
 }
 
+TEST_F(FormatTest, DontSplitLineCommentsWithEscapedNewlines) {
+  EXPECT_EQ("// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \\\n"
+            "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \\\n"
+            "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+            format("// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \\\n"
+                   "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \\\n"
+                   "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"));
+}
+
 TEST_F(FormatTest, PriorityOfCommentBreaking) {
   EXPECT_EQ("if (xxx == yyy && // aaaaaaaaaaaa\n"
             "                  // bbbbbbbbb\n"
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