Port more things!

Myriad/Serialization/OptionalConverter.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Reflection;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+using Myriad.Utils;
+
+namespace Myriad.Serialization
+{
+    public class OptionalConverter: JsonConverter<IOptional>
+    {
+        public override IOptional? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            var innerType = typeToConvert.GetGenericArguments()[0];
+            var inner = JsonSerializer.Deserialize(ref reader, innerType, options);
+
+            // TODO: rewrite to JsonConverterFactory to cut down on reflection
+            return (IOptional?) Activator.CreateInstance(
+                typeof(Optional<>).MakeGenericType(innerType),
+                BindingFlags.Instance | BindingFlags.Public,
+                null,
+                new[] {inner}, 
+                null);
+        }
+
+        public override void Write(Utf8JsonWriter writer, IOptional value, JsonSerializerOptions options)
+        {
+            var innerType = value.GetType().GetGenericArguments()[0];
+            JsonSerializer.Serialize(writer, value.GetValue(), innerType, options);
+        }
+
+        public override bool CanConvert(Type typeToConvert)
+        {
+            if (!typeToConvert.IsGenericType)
+                return false;
+
+            if (typeToConvert.GetGenericTypeDefinition() != typeof(Optional<>))
+                return false;
+
+            return true;
+        }
+    }
+}