fix(Deserializer): properly convert collection type when setting it o…

…n the model

src/JsonApiDotNetCore/Extensions/TypeExtensions.cs

@@ -35,12 +35,12 @@ public static Type GetElementType(this IEnumerable enumerable)
         /// <summary>
         /// Creates a List{TInterface} where TInterface is the generic for type specified by t
         /// </summary>
-        public static IEnumerable<TInterface> GetEmptyCollection<TInterface>(this Type t)
+        public static IEnumerable GetEmptyCollection(this Type t)
         {
             if (t == null) throw new ArgumentNullException(nameof(t));
 
             var listType = typeof(List<>).MakeGenericType(t);
-            var list = (IEnumerable<TInterface>)Activator.CreateInstance(listType);
+            var list = (IEnumerable)Activator.CreateInstance(listType);
             return list;
         }
 

src/JsonApiDotNetCore/Internal/TypeHelper.cs

@@ -7,6 +7,14 @@ namespace JsonApiDotNetCore.Internal
 {
     public static class TypeHelper
     {
+        public static IList ConvertCollection(IEnumerable<object> collection, Type targetType)
+        {
+            var list = Activator.CreateInstance(typeof(List<>).MakeGenericType(targetType)) as IList;
+            foreach(var item in collection)
+                list.Add(ConvertType(item, targetType));
+            return list;
+        }
+
         public static object ConvertType(object value, Type type)
         {
             if (value == null)

src/JsonApiDotNetCore/Models/HasManyAttribute.cs

@@ -12,7 +12,7 @@ public override void SetValue(object entity, object newValue)
                 .GetType()
                 .GetProperty(InternalRelationshipName);
 
-            propertyInfo.SetValue(entity, newValue);        
+            propertyInfo.SetValue(entity, newValue);
         }
     }
 }

src/JsonApiDotNetCore/Serialization/JsonApiDeSerializer.cs

@@ -2,14 +2,14 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
+using JsonApiDotNetCore.Extensions;
 using JsonApiDotNetCore.Internal;
 using JsonApiDotNetCore.Internal.Generics;
 using JsonApiDotNetCore.Models;
 using JsonApiDotNetCore.Models.Operations;
 using JsonApiDotNetCore.Services;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
-using JsonApiDotNetCore.Extensions;
 
 namespace JsonApiDotNetCore.Serialization
 {
@@ -246,16 +246,18 @@ private object SetHasManyRelationship(object entity,
 
                 if (data == null) return entity;
 
-                var resourceRelationships = attr.Type.GetEmptyCollection<IIdentifiable>();
-
                 var relationshipShells = relationshipData.ManyData.Select(r =>
                 {
                     var instance = attr.Type.New<IIdentifiable>();
                     instance.StringId = r.Id;
                     return instance;
                 });
 
-                attr.SetValue(entity, relationshipShells);
+                var convertedCollection = TypeHelper.ConvertCollection(relationshipShells, attr.Type);
+
+                // var convertedCollection = TypeHelper.ConvertCollection(relationshipShells, attr.Type);
+
+                attr.SetValue(entity, convertedCollection);
             }
 
             return entity;

test/UnitTests/Extensions/TypeExtensions_Tests.cs

@@ -1,7 +1,7 @@
+using System.Collections.Generic;
+using JsonApiDotNetCore.Extensions;
 using JsonApiDotNetCore.Models;
 using Xunit;
-using JsonApiDotNetCore.Extensions;
-using System.Collections.Generic;
 
 namespace UnitTests.Extensions
 {
@@ -14,7 +14,7 @@ public void GetCollection_Creates_List_If_T_Implements_Interface()
             var type = typeof(Model);
 
             // act
-            var collection = type.GetEmptyCollection<IIdentifiable>();
+            var collection = type.GetEmptyCollection();
 
             // assert
             Assert.NotNull(collection);