[clang-format] Handle \n the same way as std::endl with stream operator.

[jeanphilippeD]

Summary

clang-format break multi-line streams after std::endl.
It now also break for '\n', the suggested replacement for std::endl: http://llvm.org/docs/CodingStandards.html#avoid-std-endl

Before:
llvm::errs() << aaaaaaaaaaaaaaaaaaaaaa << '\n' << bbbbbbbbbbbbbbbbbbbbbb

<< '\n';

llvm::errs() << aaaa << "aaaaaaaaaaaaaaaaaa\n" << bbbb

<< "bbbbbbbbbbbbbbbbbb\n";

After:
llvm::errs() << aaaaaaaaaaaaaaaaaaaaaa << '\n'

<< bbbbbbbbbbbbbbbbbbbbbb << '\n';

llvm::errs() << aaaa << "aaaaaaaaaaaaaaaaaa\n"

<< bbbb << "bbbbbbbbbbbbbbbbbb\n";

This changeset ensure that multiline streams have a line break after:
-std::endl
-'\n'
-"\n"
-"Some Text\n"

Test:
-Run unit tests
-Run clang format on Format.cpp without it making changes compared to current clang-format.

[jeanphilippeD]

Ping.
Is that patch of interest?

[djasper]

Looks good.

[jeanphilippeD]

Thanks,
Would you be happy to commit it for me since i do not have commit access.

[djasper]

Submitted as r256832.

lib/Format/ContinuationIndenter.cpp

bool ContinuationIndenter::mustBreak(const LineState &State) {
 
   // The following could be precomputed as they do not depend on the state.
   // However, as they should take effect only if the UnwrappedLine does not fit
   // into the ColumnLimit, they are checked here in the ContinuationIndenter.
   if (Style.ColumnLimit != 0 && Previous.BlockKind == BK_Block &&
       Previous.is(tok::l_brace) && !Current.isOneOf(tok::r_brace, tok::comment))
     return true;
 
-  if (Current.is(tok::lessless) && Previous.is(tok::identifier) &&
-      Previous.TokenText == "endl")
+  if (Current.is(tok::lessless) &&
+      ((Previous.is(tok::identifier) && Previous.TokenText == "endl") ||
+       (Previous.Tok.isLiteral() && (Previous.TokenText.endswith("\\n\"") ||
+                                     Previous.TokenText == "\'\\n\'"))))
     return true;
 
   return false;
 }
 
 unsigned ContinuationIndenter::addTokenToState(LineState &State, bool Newline,
                                                bool DryRun,
                                                unsigned ExtraSpaces) {

unittests/Format/FormatTest.cpp

verifyFormat("void f() {\n"
                "  CHECK_EQ(aaaa, (*bbbbbbbbb)->cccccc)\n"
                "      << \"qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq\";\n"
                "}");
 
   // Handle 'endl'.
   verifyFormat("llvm::errs() << aaaaaaaaaaaaaaaaaaaaaa << endl\n"
                "             << bbbbbbbbbbbbbbbbbbbbbb << endl;");
   verifyFormat("llvm::errs() << endl << bbbbbbbbbbbbbbbbbbbbbb << endl;");
+
+  // Handle '\n'.
+  verifyFormat("llvm::errs() << aaaaaaaaaaaaaaaaaaaaaa << \"\\n\"\n"
+               "             << bbbbbbbbbbbbbbbbbbbbbb << \"\\n\";");
+  verifyFormat("llvm::errs() << aaaaaaaaaaaaaaaaaaaaaa << \'\\n\'\n"
+               "             << bbbbbbbbbbbbbbbbbbbbbb << \'\\n\';");
+  verifyFormat("llvm::errs() << aaaa << \"aaaaaaaaaaaaaaaaaa\\n\"\n"
+               "             << bbbb << \"bbbbbbbbbbbbbbbbbb\\n\";");
+  verifyFormat("llvm::errs() << \"\\n\" << bbbbbbbbbbbbbbbbbbbbbb << \"\\n\";");
 }
 
 TEST_F(FormatTest, UnderstandsEquals) {
   verifyFormat(
       "aaaaaaaaaaaaaaaaa =\n"
       "    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;");
   verifyFormat(
       "if (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa =\n"