Encoding NaN to JSON - json

Question

My server uses ServiceStack to produce JSON, and I need to send double[] arrays containing NaNs to the browsers.
Since there's no standard way of encoding NaNs in JSON, it's not surprising that
ServiceStack produces invalid JSON in presence of NaNs
(e.g. [0,NaN,42]). I chose string values as my custom representation of NaNs (and ±Inf by the way):
[0,"NaN",42,"Inf","-Inf"] as an example. (Of course I implemented the necessary post-processing on the browser side, too).
I managed to do it by setting JsConfig<double>.RawSerializeFn to an encoder function.
That was fine, until I realized that as a side effect all DTO properties of type double
disappear from their JSON representation when the value is 0.
EDIT: this can be demonstrated by new KeyValuePair<double, double>(0, 1).ToJson()
which returns {"Key":0,"Value":1} when JsConfig<double>.RawSerializeFn is unset,
but returns {"Value":1} when JsConfig<double>.RawSerializeFn is set.
This change is a side effect that I want to avoid. (But my core problem is the transmitting of NaNs without sacrificing zero-valued DTO properties.)
I browsed the source code
of ServiceStack and it confirmed that the presence
of a custom RawSerializeFn activates the Equals(DefaultValue,propertyValue) check
(by causing propertySuppressDefaultConfig==true), which was omitted by default.
AFAICS the only way to avoid this check is setting JsConfig.IncludeNullValues=true,
which is bad because it cannot be done for double values only. I need the
default behavior: omitting properties with null values (for reference types) and include 0.0 double values in the generated JSON.
How to achieve these?

Answer 1

This custom RawSerializeFn emits 0 values in the latest version of ServiceStack.Text
JsConfig<double>.IncludeDefaultValue = true;
JsConfig<double>.RawSerializeFn = d =>
double.IsPositiveInfinity(d) ?
"\"+Inf\""
: double.IsNegativeInfinity(d) ?
"\"-Inf\""
: double.IsNaN(d) ?
"\"NaN\""
: d.ToString();
var doubles = new[] {
0.0, 1.0, double.NegativeInfinity, double.NaN, double.PositiveInfinity };
doubles.ToJson().Print(); // [0,1,"-Inf","NaN","+Inf"]
new KeyValuePair<double, double>(0, 1).ToJson().Print(); // {"Key":0,"Value":1}