Support ReadAsPropertyName and WriteAsPropertyName in System.Text.Json support

[Khitiara]

ReadAsPropertyName and WriteAsPropertyName are virtual methods on JsonConverter used to support custom key types for dictionary serialization, and currently throw an exception in the case of smartenums

[ardalis]

Can you provide some code showing how this would be used with a SmartEnum?

A failing unit test that, when passing, demonstrated the behavior you seek is working would be ideal.

[Khitiara]

https://gist.github.com/Khitiara/9198a97340b4a0286405e10216392606

[Khitiara]

Here's an implementation for value converter for the special case of SmartEnum<T, string> that I'm using as a temporary workaround in the project I need this feature for, though the methods to implement dont seem to be exposed until .NET 6 or later

class SmartEnumSlugValueConverter<TEnum> : JsonConverter<TEnum>
    where TEnum : SmartEnum<TEnum, string>
{
    public override TEnum? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) =>
        reader.GetString() is { } str ? SmartEnum<TEnum, string>.FromValue(str) : null;

    public override TEnum ReadAsPropertyName(ref Utf8JsonReader reader, Type typeToConvert,
        JsonSerializerOptions options) =>
        SmartEnum<TEnum, string>.FromValue(reader.GetString() ?? throw new JsonException());


    public override void Write(Utf8JsonWriter writer, TEnum value, JsonSerializerOptions options) =>
        writer.WriteStringValue(value.Value);

    public override void WriteAsPropertyName(Utf8JsonWriter writer, TEnum value, JsonSerializerOptions options) =>
        writer.WritePropertyName(value.Value);
}