Support kinds of emitter format-setting for YAML::Null. (#906)

* Support kinds of emitter format-setting for YAML::Null.

* update the code and test cases

* add the comment //fallthrough

include/yaml-cpp/emitter.h

@@ -50,6 +50,7 @@ class YAML_CPP_API Emitter {
   bool SetOutputCharset(EMITTER_MANIP value);
   bool SetStringFormat(EMITTER_MANIP value);
   bool SetBoolFormat(EMITTER_MANIP value);
+  bool SetNullFormat(EMITTER_MANIP value);
   bool SetIntBase(EMITTER_MANIP value);
   bool SetSeqFormat(EMITTER_MANIP value);
   bool SetMapFormat(EMITTER_MANIP value);
@@ -123,6 +124,7 @@ class YAML_CPP_API Emitter {
   void SpaceOrIndentTo(bool requireSpace, std::size_t indent);
 
   const char* ComputeFullBoolName(bool b) const;
+  const char* ComputeNullName() const;
   bool CanEmitNewline() const;
 
  private:

include/yaml-cpp/emittermanip.h

@@ -26,6 +26,12 @@ enum EMITTER_MANIP {
   DoubleQuoted,
   Literal,
 
+  // null manipulators
+  LowerNull,
+  UpperNull,
+  CamelNull,
+  TildeNull,
+
   // bool manipulators
   YesNoBool,      // yes, no
   TrueFalseBool,  // true, false

src/emitter.cpp

@@ -49,6 +49,10 @@ bool Emitter::SetBoolFormat(EMITTER_MANIP value) {
   return ok;
 }
 
+bool Emitter::SetNullFormat(EMITTER_MANIP value) {
+  return m_pState->SetNullFormat(value, FmtScope::Global);
+}
+
 bool Emitter::SetIntBase(EMITTER_MANIP value) {
   return m_pState->SetIntFormat(value, FmtScope::Global);
 }
@@ -770,6 +774,21 @@ const char* Emitter::ComputeFullBoolName(bool b) const {
                          // these answers
 }
 
+const char* Emitter::ComputeNullName() const {
+  switch (m_pState->GetNullFormat()) {
+    case LowerNull:
+      return "null";
+    case UpperNull:
+      return "NULL";
+    case CamelNull:
+      return "Null";
+    case TildeNull:
+      // fallthrough
+    default:
+      return "~";
+  }
+}
+
 Emitter& Emitter::Write(bool b) {
   if (!good())
     return *this;
@@ -893,7 +912,7 @@ Emitter& Emitter::Write(const _Null& /*null*/) {
 
   PrepareNode(EmitterNodeType::Scalar);
 
-  m_stream << "~";
+  m_stream << ComputeNullName();
 
   StartedScalar();
 

src/emitterstate.cpp

@@ -13,6 +13,7 @@ EmitterState::EmitterState()
       m_boolFmt(TrueFalseBool),
       m_boolLengthFmt(LongBool),
       m_boolCaseFmt(LowerCase),
+      m_nullFmt(TildeNull),
       m_intFmt(Dec),
       m_indent(2),
       m_preCommentIndent(2),
@@ -43,6 +44,7 @@ void EmitterState::SetLocalValue(EMITTER_MANIP value) {
   SetBoolFormat(value, FmtScope::Local);
   SetBoolCaseFormat(value, FmtScope::Local);
   SetBoolLengthFormat(value, FmtScope::Local);
+  SetNullFormat(value, FmtScope::Local);
   SetIntFormat(value, FmtScope::Local);
   SetFlowType(GroupType::Seq, value, FmtScope::Local);
   SetFlowType(GroupType::Map, value, FmtScope::Local);
@@ -279,6 +281,19 @@ bool EmitterState::SetBoolCaseFormat(EMITTER_MANIP value,
   }
 }
 
+bool EmitterState::SetNullFormat(EMITTER_MANIP value, FmtScope::value scope) {
+  switch (value) {
+    case LowerNull:
+    case UpperNull:
+    case CamelNull:
+    case TildeNull:
+      _Set(m_nullFmt, value, scope);
+      return true;
+    default:
+      return false;
+  }
+}
+
 bool EmitterState::SetIntFormat(EMITTER_MANIP value, FmtScope::value scope) {
   switch (value) {
     case Dec:

src/emitterstate.h

@@ -91,6 +91,9 @@ class EmitterState {
   bool SetBoolCaseFormat(EMITTER_MANIP value, FmtScope::value scope);
   EMITTER_MANIP GetBoolCaseFormat() const { return m_boolCaseFmt.get(); }
 
+  bool SetNullFormat(EMITTER_MANIP value, FmtScope::value scope);
+  EMITTER_MANIP GetNullFormat() const { return m_nullFmt.get(); }
+
   bool SetIntFormat(EMITTER_MANIP value, FmtScope::value scope);
   EMITTER_MANIP GetIntFormat() const { return m_intFmt.get(); }
 
@@ -131,6 +134,7 @@ class EmitterState {
   Setting<EMITTER_MANIP> m_boolFmt;
   Setting<EMITTER_MANIP> m_boolLengthFmt;
   Setting<EMITTER_MANIP> m_boolCaseFmt;
+  Setting<EMITTER_MANIP> m_nullFmt;
   Setting<EMITTER_MANIP> m_intFmt;
   Setting<std::size_t> m_indent;
   Setting<std::size_t> m_preCommentIndent, m_postCommentIndent;

test/integration/emitter_test.cpp

@@ -1047,6 +1047,45 @@ TEST_F(EmitterTest, BoolFormatting) {
       "- Y\n- Y\n- y\n- N\n- N\n- n");
 }
 
+TEST_F(EmitterTest, GlobalNullFormatting) {
+  out << Flow << BeginSeq;
+  out.SetNullFormat(LowerNull);
+  out << Null;
+  out.SetNullFormat(UpperNull);
+  out << Null;
+  out.SetNullFormat(CamelNull);
+  out << Null;
+  out.SetNullFormat(TildeNull);
+  out << Null;
+  out << EndSeq;
+  ExpectEmit("[null, NULL, Null, ~]");
+}
+
+TEST_F(EmitterTest, NullFormatting) {
+  out << Flow << BeginSeq;
+  out << LowerNull << Null;
+  out << UpperNull << Null;
+  out << CamelNull << Null;
+  out << TildeNull << Null;
+  out << EndSeq;
+  ExpectEmit("[null, NULL, Null, ~]");
+}
+
+TEST_F(EmitterTest, NullFormattingOnNode) {
+  Node n(Load("null"));
+  out << Flow << BeginSeq;
+  out.SetNullFormat(LowerNull);
+  out << n;
+  out.SetNullFormat(UpperNull);
+  out << n;
+  out.SetNullFormat(CamelNull);
+  out << n;
+  out.SetNullFormat(TildeNull);
+  out << n;
+  out << EndSeq;
+  ExpectEmit("[null, NULL, Null, ~]");
+}
+
 // TODO: Fix this test.
 // TEST_F(EmitterTest, DocStartAndEnd) {
 //  out << BeginDoc;