Emitter: produce string with trailing '.0' for floating point value with only integral part

For example the number 1.0 will be converted to "1.0" instead of "1".
This allows to keep the correct type information when parsing back the YAML.

This patch is equivalent of jbeder#1377 but for the 0.8.0 version of yaml-cpp.

Author: romainreignier

include/yaml-cpp/emitter.h

@@ -162,25 +162,32 @@ inline Emitter& Emitter::WriteStreamable(T value) {
 
   bool special = false;
   if (std::is_floating_point<T>::value) {
+    special = true;
     if ((std::numeric_limits<T>::has_quiet_NaN ||
          std::numeric_limits<T>::has_signaling_NaN) &&
         std::isnan(value)) {
-      special = true;
-      stream << ".nan";
+      m_stream << ".nan";
     } else if (std::numeric_limits<T>::has_infinity && std::isinf(value)) {
-      special = true;
       if (std::signbit(value)) {
-        stream << "-.inf";
+        m_stream << "-.inf";
       } else {
-        stream << ".inf";
+        m_stream << ".inf";
       }
+    } else {
+      stream << value;
+      std::string result = stream.str();
+      if (result.find('.') == std::string::npos &&
+          result.find('e') == std::string::npos) {
+        result += ".0";
+      }
+      m_stream << result;
     }
   }
 
   if (!special) {
     stream << value;
+    m_stream << stream.str();
   }
-  m_stream << stream.str();
 
   StartedScalar();
 

test/integration/emitter_test.cpp

@@ -101,12 +101,17 @@ TEST_F(EmitterTest, NumberPrecision) {
   out.SetFloatPrecision(3);
   out.SetDoublePrecision(2);
   out << BeginSeq;
+  out << 1.0f;
   out << 3.1425926f;
+  out << 0.0;
+  out << 1.0;
   out << 53.5893;
   out << 2384626.4338;
+  out << 1999926.4338;
+  out << 9999926.4338;
   out << EndSeq;
 
-  ExpectEmit("- 3.14\n- 54\n- 2.4e+06");
+  ExpectEmit("- 1.0\n- 3.14\n- 0.0\n- 1.0\n- 54.0\n- 2.4e+06\n- 2e+06\n- 1e+07");
 }
 
 TEST_F(EmitterTest, SimpleSeq) {