[clang-format] Indent the same amount a sequence of string literals

[krasimir]

Summary

Currently clang-format indents the second in a sequence of string literals:
Code before:

"line 1"
    "line 2";

This is undesirable however, since the second string literal might have been
introduced as a result of string breaking during a previous clang-format run.
This patch makes clang-format to not indent the second and next string literals.
Code after:

"line 1"
"line 2"

[krasimir]

this is nonsense

lib/Format/ContinuationIndenter.cpp

unsigned ContinuationIndenter::getNewLineColumn(const LineState &State) {
   if (NextNonComment->is(TT_CtorInitializerColon))
     return State.FirstIndent + Style.ConstructorInitializerIndentWidth;
   if (NextNonComment->is(TT_CtorInitializerComma))
     return State.Stack.back().Indent;
   if (Previous.is(tok::r_paren) && !Current.isBinaryOperator() &&
       !Current.isOneOf(tok::colon, tok::comment))
     return ContinuationIndent;
   if (State.Stack.back().Indent == State.FirstIndent && PreviousNonComment &&
-      PreviousNonComment->isNot(tok::r_brace))
+      PreviousNonComment->isNot(tok::r_brace) &&
+      // Don't indent the second and next in a sequence of string literals.
+      // Such sequence might have been introduced by string literal breaking,
+      // so this is important to preserve idempotency.
+      !(PreviousNonComment->isStringLiteral() && Current.isStringLiteral()))
     // Ensure that we fall back to the continuation indent width instead of
     // just flushing continuations left.
     return State.Stack.back().Indent + Style.ContinuationIndentWidth;
   return State.Stack.back().Indent;
 }
 
 unsigned ContinuationIndenter::moveStateToNextToken(LineState &State,
                                                     bool DryRun, bool Newline) {

unittests/Format/FormatTest.cpp

EXPECT_EQ("\"test\"\n"
             "\"000001\"",
             format("\"test\\000000000001\"", getLLVMStyleWithColumns(9)));
   EXPECT_EQ("\"test\\000\"\n"
             "\"00000000\"\n"
             "\"1\"",
             format("\"test\\000000000001\"", getLLVMStyleWithColumns(10)));
 }
 
+TEST_F(FormatTest, KeepsIndentInASequenceOfStringLiteralsTheSame) {
+  verifyFormat("\"line 1\"\n"
+               "\"line 2\"");
+  verifyFormat("f(\"line 1\"\n"
+               "  \"line 2\");");
+  verifyFormat("{\n"
+               "  std::string a = \"line 1\"\n"
+               "                  \"line 2\"\n"
+               "                  \"line 3\";\n"
+               "}");
+  verifyFormat("auto a = \"line 1\"\n"
+               "         u\"line 2\";");
+  verifyFormat("@\"line 1\"\n"
+               "@\"line 2\";");
+}
+
 TEST_F(FormatTest, DoNotCreateUnreasonableUnwrappedLines) {
   verifyFormat("void f() {\n"
                "  return g() {}\n"
                "  void h() {}");
   verifyFormat("int a[] = {void forgot_closing_brace(){f();\n"
                "g();\n"
                "}");
 }
TEST_F(ReplacementTest, SortIncludesAfterReplacement) {
   Style.SortIncludes = true;
   auto FormattedReplaces = formatReplacements(Code, Replaces, Style);
   EXPECT_TRUE(static_cast<bool>(FormattedReplaces))
       << llvm::toString(FormattedReplaces.takeError()) << "\n";
   auto Result = applyAllReplacements(Code, *FormattedReplaces);
   EXPECT_TRUE(static_cast<bool>(Result));
   EXPECT_EQ(Expected, *Result);
 }
-
 } // end namespace
 } // end namespace format
 } // end namespace clang