Adding support for custom JsonConverter(s) when deserializing JSON Patch value object

src/Features/JsonPatch/src/Internal/ConversionResultProvider.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Reflection;
 using Newtonsoft.Json;
+using Newtonsoft.Json.Serialization;
 
 namespace Microsoft.AspNetCore.JsonPatch.Internal
 {
@@ -14,6 +15,11 @@ namespace Microsoft.AspNetCore.JsonPatch.Internal
     public static class ConversionResultProvider
     {
         public static ConversionResult ConvertTo(object value, Type typeToConvertTo)
+        {
+            return ConvertTo(value, typeToConvertTo, null);
+        }
+
+        internal static ConversionResult ConvertTo(object value, Type typeToConvertTo, IContractResolver contractResolver)
         {
             if (value == null)
             {
@@ -28,8 +34,20 @@ public static ConversionResult ConvertTo(object value, Type typeToConvertTo)
             {
                 try
                 {
-                    var deserialized = JsonConvert.DeserializeObject(JsonConvert.SerializeObject(value), typeToConvertTo);
-                    return new ConversionResult(true, deserialized);
+                    if (contractResolver == null)
+                    {
+                        var deserialized = JsonConvert.DeserializeObject(JsonConvert.SerializeObject(value), typeToConvertTo);
+                        return new ConversionResult(true, deserialized);
+                    }
+                    else
+                    {
+                        var serializerSettings = new JsonSerializerSettings()
+                        {
+                            ContractResolver = contractResolver
+                        };
+                        var deserialized = JsonConvert.DeserializeObject(JsonConvert.SerializeObject(value), typeToConvertTo, serializerSettings);
+                        return new ConversionResult(true, deserialized);
+                    }
                 }
                 catch
                 {

src/Features/JsonPatch/src/Internal/ListAdapter.cs

@@ -36,7 +36,7 @@ public virtual bool TryAdd(
                 return false;
             }
 
-            if (!TryConvertValue(value, typeArgument, segment, out var convertedValue, out errorMessage))
+            if (!TryConvertValue(value, typeArgument, segment, contractResolver, out var convertedValue, out errorMessage))
             {
                 return false;
             }
@@ -138,7 +138,7 @@ public virtual bool TryReplace(
                 return false;
             }
 
-            if (!TryConvertValue(value, typeArgument, segment, out var convertedValue, out errorMessage))
+            if (!TryConvertValue(value, typeArgument, segment, contractResolver, out var convertedValue, out errorMessage))
             {
                 return false;
             }
@@ -175,7 +175,7 @@ public virtual bool TryTest(
                 return false;
             }
 
-            if (!TryConvertValue(value, typeArgument, segment, out var convertedValue, out errorMessage))
+            if (!TryConvertValue(value, typeArgument, segment, contractResolver, out var convertedValue, out errorMessage))
             {
                 return false;
             }
@@ -235,7 +235,24 @@ protected virtual bool TryConvertValue(
             out object convertedValue,
             out string errorMessage)
         {
-            var conversionResult = ConversionResultProvider.ConvertTo(originalValue, listTypeArgument);
+            return TryConvertValue(
+                originalValue,
+                listTypeArgument,
+                segment,
+                null,
+                out convertedValue,
+                out errorMessage);
+        }
+
+        protected virtual bool TryConvertValue(
+            object originalValue,
+            Type listTypeArgument,
+            string segment,
+            IContractResolver contractResolver,
+            out object convertedValue,
+            out string errorMessage)
+        {
+            var conversionResult = ConversionResultProvider.ConvertTo(originalValue, listTypeArgument, contractResolver);
             if (!conversionResult.CanBeConverted)
             {
                 convertedValue = null;

src/Features/JsonPatch/src/PublicAPI.Unshipped.txt

@@ -1 +1,2 @@
 #nullable enable
+~virtual Microsoft.AspNetCore.JsonPatch.Internal.ListAdapter.TryConvertValue(object originalValue, System.Type listTypeArgument, string segment, Newtonsoft.Json.Serialization.IContractResolver contractResolver, out object convertedValue, out string errorMessage) -> bool

src/Features/JsonPatch/test/IntegrationTests/HeterogenousCollectionTests.cs

@@ -0,0 +1,103 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
+using Newtonsoft.Json.Linq;
+using Newtonsoft.Json.Serialization;
+using Xunit;
+
+namespace Microsoft.AspNetCore.JsonPatch.IntegrationTests
+{
+    public class HeterogenousCollectionTests
+    {
+        [Fact]
+        public void AddItemToList()
+        {
+            // Arrange
+            var targetObject = new Canvas()
+            {
+                Items = new List<Shape>()
+            };
+
+            var circleJObject = JObject.Parse(@"{
+              Type: 'Circle',
+              ShapeProperty: 'Shape property',
+              CircleProperty: 'Circle property'
+            }");
+
+            var patchDocument = new JsonPatchDocument
+            {
+                ContractResolver = new CanvasContractResolver()
+            };
+
+            patchDocument.Add("/Items/-", circleJObject);
+
+            // Act
+            patchDocument.ApplyTo(targetObject);
+
+            // Assert
+            var circle = targetObject.Items[0] as Circle;
+            Assert.NotNull(circle);
+            Assert.Equal("Shape property", circle.ShapeProperty);
+            Assert.Equal("Circle property", circle.CircleProperty);
+        }
+    }
+
+    public class CanvasContractResolver : DefaultContractResolver
+    {
+        protected override JsonConverter ResolveContractConverter(Type objectType)
+        {
+            if (objectType == typeof(Shape))
+            {
+                return new ShapeJsonConverter();
+            }
+
+            return base.ResolveContractConverter(objectType);
+        }
+    }
+
+    public class ShapeJsonConverter : CustomCreationConverter<Shape>
+    {
+        private const string TypeProperty = "Type";
+
+        public override bool CanRead => true;
+
+        public override Shape Create(Type objectType)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override object ReadJson(
+            JsonReader reader,
+            Type objectType,
+            object existingValue,
+            JsonSerializer serializer)
+        {
+            var jObject = JObject.Load(reader);
+
+            var target = CreateShape(jObject);
+            serializer.Populate(jObject.CreateReader(), target);
+
+            return target;
+        }
+
+        private Shape CreateShape(JObject jObject)
+        {
+            var typeProperty = jObject.GetValue(TypeProperty).ToString();
+
+            switch (typeProperty)
+            {
+                case "Circle":
+                    return new Circle();
+
+                case "Rectangle":
+                    return new Rectangle();
+            }
+
+            throw new NotSupportedException();
+        }
+    }
+}