Added ARDUINOJSON_ENABLE_NAN to enable NaN in JSON (closes #973)

test/MixedConfiguration/CMakeLists.txt

@@ -12,6 +12,8 @@ add_executable(MixedConfigurationTests
 	use_double_1.cpp
 	use_long_long_0.cpp
 	use_long_long_1.cpp
+	enable_nan_0.cpp
+	enable_nan_1.cpp
 )
 
 target_link_libraries(MixedConfigurationTests catch)

test/MixedConfiguration/enable_nan_0.cpp

@@ -0,0 +1,25 @@
+#define ARDUINOJSON_ENABLE_NAN 0
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+#include <limits>
+
+TEST_CASE("ARDUINOJSON_ENABLE_NAN == 0") {
+  DynamicJsonDocument doc(4096);
+  JsonObject root = doc.to<JsonObject>();
+
+  SECTION("serializeJson()") {
+    root["X"] = std::numeric_limits<double>::signaling_NaN();
+
+    std::string json;
+    serializeJson(doc, json);
+
+    REQUIRE(json == "{\"X\":null}");
+  }
+
+  SECTION("deserializeJson()") {
+    auto err = deserializeJson(doc, "{\"X\":NaN}");
+
+    REQUIRE(err == DeserializationError::InvalidInput);
+  }
+}

test/MixedConfiguration/enable_nan_1.cpp

@@ -0,0 +1,31 @@
+#define ARDUINOJSON_ENABLE_NAN 1
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+#include <limits>
+
+namespace my {
+using ARDUINOJSON_NAMESPACE::isnan;
+}  // namespace my
+
+TEST_CASE("ARDUINOJSON_ENABLE_NAN == 1") {
+  DynamicJsonDocument doc(4096);
+  JsonObject root = doc.to<JsonObject>();
+
+  SECTION("serializeJson()") {
+    root["X"] = std::numeric_limits<double>::signaling_NaN();
+
+    std::string json;
+    serializeJson(doc, json);
+
+    REQUIRE(json == "{\"X\":NaN}");
+  }
+
+  SECTION("deserializeJson()") {
+    auto err = deserializeJson(doc, "{\"X\":NaN}");
+    float x = doc["X"];
+
+    REQUIRE(err == DeserializationError::Ok);
+    REQUIRE(my::isnan(x));
+  }
+}