Merge pull request #2166 from erri120/fix/windowdata-serialization

Add `Optional<T>` JSON converter

src/NexusMods.DataModel/JsonConverters/OptionalConverter.cs

@@ -0,0 +1,69 @@
+using System.Reflection;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using DynamicData.Kernel;
+using JetBrains.Annotations;
+
+namespace NexusMods.DataModel.JsonConverters;
+
+/// <summary>
+/// Converter factory for <see cref="Optional{T}"/>
+/// </summary>
+[UsedImplicitly]
+public class OptionalConverterFactory : JsonConverterFactory
+{
+    /// <inheritdoc/>
+    public override bool CanConvert(Type typeToConvert)
+    {
+        if (!typeToConvert.IsGenericType) return false;
+        return typeToConvert.GetGenericTypeDefinition() == typeof(Optional<>);
+    }
+
+    /// <inheritdoc/>
+    public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options)
+    {
+        var typeArguments = typeToConvert.GetGenericArguments();
+        var valueType = typeArguments[0];
+
+        var converter = (JsonConverter)Activator.CreateInstance(
+            type: typeof(OptionalConverter<>).MakeGenericType(valueType),
+            bindingAttr: BindingFlags.Instance | BindingFlags.Public,
+            binder: null,
+            args: [options],
+            culture: null
+        )!;
+
+        return converter;
+    }
+
+    private class OptionalConverter<TValue> : JsonConverter<Optional<TValue>>
+        where TValue : notnull
+    {
+        private readonly JsonConverter<TValue> _valueConverter;
+
+        [UsedImplicitly]
+        public OptionalConverter(JsonSerializerOptions options)
+        {
+            _valueConverter = (JsonConverter<TValue>)options.GetConverter(typeof(TValue));
+        }
+
+        public override Optional<TValue> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            if (reader.TokenType == JsonTokenType.Null) return Optional<TValue>.None;
+            var value = _valueConverter.Read(ref reader, typeToConvert, options);
+            return Optional<TValue>.Create(value);
+        }
+
+        public override void Write(Utf8JsonWriter writer, Optional<TValue> value, JsonSerializerOptions options)
+        {
+            if (!value.HasValue)
+            {
+                writer.WriteNullValue();
+            }
+            else
+            {
+                _valueConverter.Write(writer, value.Value, options);
+            }
+        }
+    }
+}

src/NexusMods.DataModel/Services.cs

@@ -86,7 +86,9 @@ public static IServiceCollection AddDataModel(this IServiceCollection coll)
         coll.AddSingleton<JsonConverter, GamePathConverter>();
         coll.AddSingleton<JsonConverter, DateTimeConverter>();
         coll.AddSingleton<JsonConverter, SizeConverter>();
-
+        coll.AddSingleton<JsonConverterFactory, OptionalConverterFactory>();
+        coll.AddSingleton<JsonConverter, OptionalConverterFactory>();
+
         // Game Registry
         coll.AddSingleton<IGameRegistry, GameRegistry>();
         coll.AddHostedService(s => (GameRegistry)s.GetRequiredService<IGameRegistry>());