Bugfix: Respect customizations on JsonSerializerSettings

benchmarks/Serialization/JsonApiSerializerBenchmarks.cs

@@ -1,5 +1,6 @@
 using System;
 using BenchmarkDotNet.Attributes;
+using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Internal.Contracts;
 using JsonApiDotNetCore.Managers;
 using JsonApiDotNetCore.Query;
@@ -23,6 +24,8 @@ public class JsonApiSerializerBenchmarks
 
         public JsonApiSerializerBenchmarks()
         {
+            var options = new JsonApiOptions();
+
             IResourceGraph resourceGraph = DependencyFactory.CreateResourceGraph();
             IFieldsToSerialize fieldsToSerialize = CreateFieldsToSerialize(resourceGraph);
 
@@ -33,7 +36,7 @@ public JsonApiSerializerBenchmarks()
             var resourceObjectBuilder = new ResourceObjectBuilder(resourceGraph, new ResourceObjectBuilderSettings());
 
             _jsonApiSerializer = new ResponseSerializer<BenchmarkResource>(metaBuilderMock.Object, linkBuilderMock.Object,
-                includeBuilderMock.Object, fieldsToSerialize, resourceObjectBuilder);
+                includeBuilderMock.Object, fieldsToSerialize, resourceObjectBuilder, options);
         }
 
         private static FieldsToSerialize CreateFieldsToSerialize(IResourceGraph resourceGraph)

src/JsonApiDotNetCore/Configuration/IJsonApiOptions.cs

@@ -1,3 +1,5 @@
+using Newtonsoft.Json;
+
 namespace JsonApiDotNetCore.Configuration
 {
     public interface IJsonApiOptions : ILinksConfiguration, ISerializerOptions
@@ -25,6 +27,7 @@ public interface IJsonApiOptions : ILinksConfiguration, ISerializerOptions
         bool AllowClientGeneratedIds { get; }
         bool AllowCustomQueryParameters { get; set; }
         string Namespace { get; set; }
+        JsonSerializerSettings SerializerSettings { get; }
     }
 
     public interface ISerializerOptions

src/JsonApiDotNetCore/Configuration/JsonApiOptions.cs

@@ -140,7 +140,7 @@ public class JsonApiOptions : IJsonApiOptions
         /// </example>
         public bool ValidateModelState { get; set; }
 
-        public JsonSerializerSettings SerializerSettings { get; } = new JsonSerializerSettings()
+        public JsonSerializerSettings SerializerSettings { get; } = new JsonSerializerSettings
         {
             NullValueHandling = NullValueHandling.Ignore
         };

src/JsonApiDotNetCore/Internal/Exceptions/ErrorCollection.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
+using JsonApiDotNetCore.Serialization.Common;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Serialization;
 using Microsoft.AspNetCore.Mvc;
@@ -20,12 +21,17 @@ public void Add(Error error)
             Errors.Add(error);
         }
 
-        public string GetJson()
+        public string GetJson(JsonSerializerSettings serializerSettings)
         {
-            return JsonConvert.SerializeObject(this, new JsonSerializerSettings {
-                NullValueHandling = NullValueHandling.Ignore,
-                ContractResolver = new CamelCasePropertyNamesContractResolver()
-            });
+            var beforeContractResolver = serializerSettings.ContractResolver;
+            serializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
+
+            using var scope = new JsonSerializerSettingsNullValueHandlingScope(serializerSettings, NullValueHandling.Ignore);
+            string json = JsonConvert.SerializeObject(this, serializerSettings);
+
+            serializerSettings.ContractResolver = beforeContractResolver;
+
+            return json;
         }
 
         public int GetErrorStatusCode()

src/JsonApiDotNetCore/Serialization/Common/JsonSerializerSettingsNullValueHandlingScope.cs

@@ -0,0 +1,30 @@
+using System;
+using Newtonsoft.Json;
+
+namespace JsonApiDotNetCore.Serialization.Common
+{
+    /// <summary>
+    /// Used to temporarily switch to a different <see cref="JsonSerializerSettings.NullValueHandling"/> value while preserving other settings.
+    /// After disposal, the original NullValueHandling value is restored.
+    /// </summary>
+    internal sealed class JsonSerializerSettingsNullValueHandlingScope : IDisposable
+    {
+        private readonly NullValueHandling _beforeNullValueHandling;
+
+        public JsonSerializerSettings Settings { get; set; }
+
+        public JsonSerializerSettingsNullValueHandlingScope(JsonSerializerSettings settings,
+            NullValueHandling nullValueHandling)
+        {
+            _beforeNullValueHandling = settings.NullValueHandling;
+            Settings = settings;
+
+            Settings.NullValueHandling = nullValueHandling;
+        }
+
+        public void Dispose()
+        {
+            Settings.NullValueHandling = _beforeNullValueHandling;
+        }
+    }
+}