[clang-tidy] Fix the YAML created for checks like modernize-pass-by-v…

…alue

Currently this check generates the replacement with the newline in the end.
The proper way to export it to YAML is to have two \n\n instead of one.
Without this fix clients should reinterpret the replacement as
"#include <utility> " instead of "#include <utility>\n"

Differential Revision: https://reviews.llvm.org/D63482

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@365017 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Tooling/ReplacementsYaml.h

@@ -35,7 +35,13 @@ template <> struct MappingTraits<clang::tooling::Replacement> {
 
     NormalizedReplacement(const IO &, const clang::tooling::Replacement &R)
         : FilePath(R.getFilePath()), Offset(R.getOffset()),
-          Length(R.getLength()), ReplacementText(R.getReplacementText()) {}
+          Length(R.getLength()), ReplacementText(R.getReplacementText()) {
+      size_t lineBreakPos = ReplacementText.find('\n');
+      while (lineBreakPos != std::string::npos) {
+        ReplacementText.replace(lineBreakPos, 1, "\n\n");
+        lineBreakPos = ReplacementText.find('\n', lineBreakPos + 2);
+      }
+    }
 
     clang::tooling::Replacement denormalize(const IO &) {
       return clang::tooling::Replacement(FilePath, Offset, Length,

unittests/Tooling/ReplacementsYamlTest.cpp

@@ -46,6 +46,30 @@ TEST(ReplacementsYamlTest, serializesReplacements) {
                YamlContentStream.str().c_str());
 }
 
+TEST(ReplacementsYamlTest, serializesNewLines) {
+  TranslationUnitReplacements Doc;
+
+  Doc.MainSourceFile = "/path/to/source.cpp";
+  Doc.Replacements.emplace_back("/path/to/file1.h", 0, 0, "#include <utility>\n");
+
+  std::string YamlContent;
+  llvm::raw_string_ostream YamlContentStream(YamlContent);
+
+  yaml::Output YAML(YamlContentStream);
+  YAML << Doc;
+
+  // NOTE: If this test starts to fail for no obvious reason, check whitespace.
+  ASSERT_STREQ("---\n"
+               "MainSourceFile:  '/path/to/source.cpp'\n"
+               "Replacements:    \n" // Extra whitespace here!
+               "  - FilePath:        '/path/to/file1.h'\n"
+               "    Offset:          0\n"
+               "    Length:          0\n"
+               "    ReplacementText: '#include <utility>\n\n'\n"
+               "...\n",
+               YamlContentStream.str().c_str());
+}
+
 TEST(ReplacementsYamlTest, deserializesReplacements) {
   std::string YamlContent = "---\n"
                             "MainSourceFile:      /path/to/source.cpp\n"