[YAML] Fix UTF-8 handling

[thegameg]

Summary

Previous YAML quoting patches broke UTF-8 printing in YAML: see https://reviews.llvm.org/D41290#961801.

[JDevlieghere]

Makes sense to me. LGTM!

[JDevlieghere]

unittests/Support/YAMLIOTest.cpp

2546

I'd remove the double single quotes here though, it doesn't really add anything to the test case except confusion.

2559

Maybe merge this with the previous test case?

lib/Support/YAMLTraits.cpp

if (S[j] == QuoteChar) {                  // Escape quotes.
       if (MustQuote == QuotingType::Double) { // Print it as \"
         output(StringLiteral("\\"));
         output(StringRef(Quote, 1));
       } else {                       // Single
         output(StringLiteral("''")); // Print it as ''
       }
       i = j + 1;
     } else if (MustQuote == QuotingType::Double &&
-               !sys::unicode::isPrintable(S[j])) {
+               !sys::unicode::isPrintable(S[j]) && (S[j] & 0x80) == 0) {
+      // If we're double quoting non-printable characters, we prefer printing
+      // them as "\x" + their hex representation. Note that special casing is
+      // needed for UTF-8, where we want to print the non-escaped characters.
       output(StringRef(&Base[i], j - i)); // "flush"
       output(StringLiteral("\\x"));
 
       // Output the byte 0x0F as \x0f.
       auto FormattedHex = format_hex_no_prefix(S[j], 2);
       Out << FormattedHex;
       Column += 4; // one for the '\', one for the 'x', and two for the hex
 

unittests/Support/YAMLIOTest.cpp

TEST(YAMLIO, TestEscapedSingleQuoteInsideSingleQuote) {
   Output xout(ostr, nullptr, 0);
 
   llvm::yaml::EmptyContext Ctx;
   yamlize(xout, Id, true, Ctx);
 
   ostr.flush();
   EXPECT_EQ("'abc''fdf'", out);
 }
+
+TEST(YAMLIO, TestEscapedUTF8SingleQuoteInsideDoubleQuote) {
+  std::string Id = "parameter ''параметр'' is unused";
+
+  std::string out;
+  llvm::raw_string_ostream ostr(out);
+  Output xout(ostr, nullptr, 0);
+
+  llvm::yaml::EmptyContext Ctx;
+  yamlize(xout, Id, true, Ctx);
+
+  ostr.flush();
+  EXPECT_EQ("\"parameter ''параметр'' is unused\"", out);
+}
+
+TEST(YAMLIO, TestEscapedUTF8) {
+  std::string Id = "/*параметр*/";
+
+  std::string out;
+  llvm::raw_string_ostream ostr(out);
+  Output xout(ostr, nullptr, 0);
+
+  llvm::yaml::EmptyContext Ctx;
+  yamlize(xout, Id, true, Ctx);
+
+  ostr.flush();
+  EXPECT_EQ("\"/*параметр*/\"", out);
+}