Don't break line comments with escaped newlines.

Summary:
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.

Reviewers: djasper

Reviewed By: djasper

CC: cfe-commits, klimek

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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186456 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Format/Format.cpp

@@ -905,6 +905,11 @@ private:
       // Only break up default narrow strings.
       if (!Current.TokenText.startswith("\""))
         return 0;
+      // Don't break string literals with escaped newlines. As clang-format must
+      // not change the string's content, it is unlikely that we'll end up with
+      // a better format.
+      if (Current.TokenText.find("\\\n") != StringRef::npos)
+        return 0;
       // Exempts unterminated string literals from line breaking. The user will
       // likely want to terminate the string before any line breaking is done.
       if (Current.IsUnterminatedLiteral)
@@ -919,6 +924,23 @@ private:
     } 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 a single line comment with
+      // multiple lines including leading whitespace and the '//' markers.
+      //
+      // FIXME: 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.
+      StringRef::size_type EscapedNewlinePos = Current.TokenText.find("\\\n");
+      if (EscapedNewlinePos != StringRef::npos) {
+        State.Column =
+            StartColumn +
+            encoding::getCodePointCount(
+                Current.TokenText.substr(0, EscapedNewlinePos), Encoding) +
+            1;
+        return 0;
+      }
+
       Token.reset(new BreakableLineComment(Current, StartColumn,
                                            Line.InPPDirective, Encoding));
     } else {

lib/Format/TokenAnnotator.cpp

@@ -967,8 +967,9 @@ void TokenAnnotator::calculateFormattingInformation(AnnotatedLine &Line) {
                Current->is(tok::string_literal) &&
                Current->Previous->isNot(tok::lessless) &&
                Current->Previous->Type != TT_InlineASMColon &&
-               Current->getNextNonComment() &&
-               Current->getNextNonComment()->is(tok::string_literal)) {
+               ((Current->getNextNonComment() &&
+                 Current->getNextNonComment()->is(tok::string_literal)) ||
+                (Current->TokenText.find("\\\n") != StringRef::npos))) {
       Current->MustBreakBefore = true;
     }
     Current->CanBreakBefore =

unittests/Format/FormatTest.cpp

@@ -921,6 +921,32 @@ TEST_F(FormatTest, SplitsLongCxxComments) {
                    getLLVMStyleWithColumns(20)));
 }
 
+TEST_F(FormatTest, DontSplitLineCommentsWithEscapedNewlines) {
+  EXPECT_EQ("// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
+            "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
+            "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+            format("// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
+                   "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
+                   "// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"));
+  EXPECT_EQ("int a; // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\n"
+            "       // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\n"
+            "       // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
+            format("int a; // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\n"
+                   "       // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\n"
+                   "       // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
+                   getLLVMStyleWithColumns(50)));
+  // FIXME: One day we might want to implement adjustment of leading whitespace
+  // of the consecutive lines in this kind of comment:
+  EXPECT_EQ("int\n"
+            "a; // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\n"
+            "       // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\n"
+            "       // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
+            format("int a; // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\n"
+                   "       // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\\\n"
+                   "       // AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
+                   getLLVMStyleWithColumns(49)));
+}
+
 TEST_F(FormatTest, PriorityOfCommentBreaking) {
   EXPECT_EQ("if (xxx == yyy && // aaaaaaaaaaaa\n"
             "                  // bbbbbbbbb\n"
@@ -2969,6 +2995,21 @@ TEST_F(FormatTest, AlwaysBreakBeforeMultilineStrings) {
             "     \"bbbb\"\n"
             "     \"cccc\");",
             format("aaaa(qqq, \"bbbb\" \"cccc\");", Break));
+  EXPECT_EQ("x = \"a\\\n"
+            "b\\\n"
+            "c\";",
+            format("x = \"a\\\n"
+                   "b\\\n"
+                   "c\";",
+                   NoBreak));
+  EXPECT_EQ("x =\n"
+            "    \"a\\\n"
+            "b\\\n"
+            "c\";",
+            format("x = \"a\\\n"
+                   "b\\\n"
+                   "c\";",
+                   Break));
 }
 
 TEST_F(FormatTest, AlignsPipes) {
@@ -4992,6 +5033,16 @@ TEST_F(FormatTest, BreakStringLiterals) {
       format("#define A \"some text other\";", AlignLeft));
 }
 
+TEST_F(FormatTest, DontSplitStringLiteralsWithEscapedNewlines) {
+  EXPECT_EQ("aaaaaaaaaaa =\n"
+            "    \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
+            "  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
+            "  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\";",
+            format("aaaaaaaaaaa = \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
+                   "  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\\n"
+                   "  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\";"));
+}
+
 TEST_F(FormatTest, SkipsUnknownStringLiterals) {
   EXPECT_EQ(
       "u8\"unsupported literal\";",