yaml-cpp.patch

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 46dc180..b746ac1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 # 3.5 is actually available almost everywhere, but this a good minimum
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.10)
 
 # enable MSVC_RUNTIME_LIBRARY target property
 # see https://cmake.org/cmake/help/latest/policy/CMP0091.html
diff --git a/include/yaml-cpp/emittermanip.h b/include/yaml-cpp/emittermanip.h
index 976d149..ba73a48 100644
--- a/include/yaml-cpp/emittermanip.h
+++ b/include/yaml-cpp/emittermanip.h
@@ -32,6 +32,7 @@ enum EMITTER_MANIP {
   UpperNull,
   CamelNull,
   TildeNull,
+  EmptyNull,
 
   // bool manipulators
   YesNoBool,      // yes, no
diff --git a/include/yaml-cpp/exceptions.h b/include/yaml-cpp/exceptions.h
index f6b2602..a4c5537 100644
--- a/include/yaml-cpp/exceptions.h
+++ b/include/yaml-cpp/exceptions.h
@@ -87,6 +87,7 @@ const char* const INVALID_ANCHOR = "invalid anchor";
 const char* const INVALID_ALIAS = "invalid alias";
 const char* const INVALID_TAG = "invalid tag";
 const char* const BAD_FILE = "bad file";
+const char* const NON_UNIQUE_MAP_KEY = "map keys must be unique";
 
 template <typename T>
 inline const std::string KEY_NOT_FOUND_WITH_KEY(
@@ -298,6 +299,16 @@ class YAML_CPP_API BadFile : public Exception {
   BadFile(const BadFile&) = default;
   ~BadFile() YAML_CPP_NOEXCEPT override;
 };
+
+class YAML_CPP_API NonUniqueMapKey : public RepresentationException {
+ public:
+  template <typename Key>
+  NonUniqueMapKey(const Mark& mark_, const Key& key)
+      : RepresentationException(mark_, ErrorMsg::NON_UNIQUE_MAP_KEY) {}
+  NonUniqueMapKey(const NonUniqueMapKey&) = default;
+  ~NonUniqueMapKey() YAML_CPP_NOEXCEPT override;
+};
+
 }  // namespace YAML
 
 #endif  // EXCEPTIONS_H_62B23520_7C8E_11DE_8A39_0800200C9A66
diff --git a/include/yaml-cpp/node/detail/impl.h b/include/yaml-cpp/node/detail/impl.h
index b38038d..9138fe6 100644
--- a/include/yaml-cpp/node/detail/impl.h
+++ b/include/yaml-cpp/node/detail/impl.h
@@ -218,7 +218,7 @@ inline void node_data::force_insert(const Key& key, const Value& value,
 
   node& k = convert_to_node(key, pMemory);
   node& v = convert_to_node(value, pMemory);
-  insert_map_pair(k, v);
+  insert_map_pair(k, v, true);
 }
 
 template <typename T>
diff --git a/include/yaml-cpp/node/detail/node_data.h b/include/yaml-cpp/node/detail/node_data.h
index 07cf81a..ed7d9cd 100644
--- a/include/yaml-cpp/node/detail/node_data.h
+++ b/include/yaml-cpp/node/detail/node_data.h
@@ -90,7 +90,7 @@ class YAML_CPP_API node_data {
   void reset_sequence();
   void reset_map();
 
-  void insert_map_pair(node& key, node& value);
+  void insert_map_pair(node& key, node& value, bool force = false);
   void convert_to_map(const shared_memory_holder& pMemory);
   void convert_sequence_to_map(const shared_memory_holder& pMemory);
 
diff --git a/src/emitter.cpp b/src/emitter.cpp
index 4d48307..a188cca 100644
--- a/src/emitter.cpp
+++ b/src/emitter.cpp
@@ -721,7 +721,7 @@ Emitter& Emitter::Write(const std::string& str) {
 
   StringEscaping::value stringEscaping = GetStringEscapingStyle(m_pState->GetOutputCharset());
 
-  const StringFormat::value strFormat =
+  const StringFormat::value strFormat = str.compare(0, 2, "|\n") == 0 ? StringFormat::Literal :
       Utils::ComputeStringFormat(str, m_pState->GetStringFormat(),
                                  m_pState->CurGroupFlowType(), stringEscaping == StringEscaping::NonAscii);
 
@@ -816,6 +816,8 @@ const char* Emitter::ComputeNullName() const {
       return "NULL";
     case CamelNull:
       return "Null";
+    case EmptyNull:
+      return "";
     case TildeNull:
       // fallthrough
     default:
diff --git a/src/emitterstate.cpp b/src/emitterstate.cpp
index 3dbe401..0dd0b17 100644
--- a/src/emitterstate.cpp
+++ b/src/emitterstate.cpp
@@ -305,6 +305,7 @@ bool EmitterState::SetNullFormat(EMITTER_MANIP value, FmtScope::value scope) {
     case LowerNull:
     case UpperNull:
     case CamelNull:
+    case EmptyNull:
     case TildeNull:
       _Set(m_nullFmt, value, scope);
       return true;
diff --git a/src/emitterutils.cpp b/src/emitterutils.cpp
index 6cdf6de..b48b7c0 100644
--- a/src/emitterutils.cpp
+++ b/src/emitterutils.cpp
@@ -365,7 +365,7 @@ bool WriteDoubleQuotedString(ostream_wrapper& out, const std::string& str,
 
 bool WriteLiteralString(ostream_wrapper& out, const std::string& str,
                         std::size_t indent) {
-  out << "|\n";
+  out << (str.compare(0, 2, "|\n") == 0 ? "" : "|\n");
   int codePoint;
   for (std::string::const_iterator i = str.begin();
        GetNextCodePointAndAdvance(codePoint, i, str.end());) {
diff --git a/src/exceptions.cpp b/src/exceptions.cpp
index 43a7976..af99fd6 100644
--- a/src/exceptions.cpp
+++ b/src/exceptions.cpp
@@ -17,4 +17,5 @@ BadPushback::~BadPushback() YAML_CPP_NOEXCEPT = default;
 BadInsert::~BadInsert() YAML_CPP_NOEXCEPT = default;
 EmitterException::~EmitterException() YAML_CPP_NOEXCEPT = default;
 BadFile::~BadFile() YAML_CPP_NOEXCEPT = default;
+NonUniqueMapKey::~NonUniqueMapKey() YAML_CPP_NOEXCEPT = default;
 }  // namespace YAML
diff --git a/src/exp.h b/src/exp.h
index c8837f0..5db3ee4 100644
--- a/src/exp.h
+++ b/src/exp.h
@@ -118,7 +118,7 @@ inline const RegEx& ValueInJSONFlow() {
   return e;
 }
 inline const RegEx& Ampersand() {
-  static const RegEx e = RegEx('&');
+  static const RegEx e = RegEx("^&| &");
   return e;
 }
 inline const RegEx Comment() {
diff --git a/src/node_data.cpp b/src/node_data.cpp
index 8f5422a..23ad892 100644
--- a/src/node_data.cpp
+++ b/src/node_data.cpp
@@ -279,7 +279,12 @@ void node_data::reset_map() {
   m_undefinedPairs.clear();
 }
 
-void node_data::insert_map_pair(node& key, node& value) {
+void node_data::insert_map_pair(node& key, node& value, bool force) {
+  if (!force && !key.scalar().empty())
+    for (const auto& mapEntry : m_map)
+      if (mapEntry.first->scalar() == key.scalar())
+        throw NonUniqueMapKey(m_mark, key);
+
   m_map.emplace_back(&key, &value);
 
   if (!key.is_defined() || !value.is_defined())
diff --git a/test/integration/load_node_test.cpp b/test/integration/load_node_test.cpp
index 9d0c790..37355aa 100644
--- a/test/integration/load_node_test.cpp
+++ b/test/integration/load_node_test.cpp
@@ -360,5 +360,9 @@ TEST(LoadNodeTest, BlockCRNLEncoded) {
   EXPECT_EQ(1, node["followup"].as<int>());
 }
 
+TEST(LoadNodeTest, NonUniqueMapKey) {
+  EXPECT_THROW(Load("{a: A, b: B, a: A}"), NonUniqueMapKey);
+}
+
 }  // namespace
 }  // namespace YAML