fix(Deserializer): remove dependency on GenericProcessorFactory

Rather than fetching data from the database during deserialization, we can set the relationships with instances that just carry the id. It will then be the responsibility of the repository to handle those relationships

Author: jaredcnance

src/JsonApiDotNetCore/Extensions/TypeExtensions.cs

@@ -31,5 +31,28 @@ public static Type GetElementType(this IEnumerable enumerable)
 
             return elementType;
         }
+
+        /// <summary>
+        /// Creates a List{TInterface} where TInterface is the generic for type specified by t
+        /// </summary>
+        public static List<TInterface> GetEmptyCollection<TInterface>(this Type t)
+        {
+            if (t == null) throw new ArgumentNullException(nameof(t));
+
+            var listType = typeof(List<>).MakeGenericType(t);
+            var list = (List<TInterface>)Activator.CreateInstance(listType);
+            return list;
+        }
+
+        /// <summary>
+        /// Creates a new instance of type t, casting it to the specified TInterface 
+        /// </summary>
+        public static TInterface New<TInterface>(this Type t)
+        {
+            if (t == null) throw new ArgumentNullException(nameof(t));
+
+            var instance = (TInterface)Activator.CreateInstance(t);
+            return instance;
+        }
     }
 }

src/JsonApiDotNetCore/Serialization/JsonApiDeSerializer.cs

@@ -9,20 +9,27 @@
 using JsonApiDotNetCore.Services;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
+using JsonApiDotNetCore.Extensions;
 
 namespace JsonApiDotNetCore.Serialization
 {
     public class JsonApiDeSerializer : IJsonApiDeSerializer
     {
         private readonly IJsonApiContext _jsonApiContext;
-        private readonly IGenericProcessorFactory _genericProcessorFactory;
 
+        [Obsolete(
+            "The deserializer no longer depends on the IGenericProcessorFactory",
+            error: false)]
         public JsonApiDeSerializer(
             IJsonApiContext jsonApiContext,
             IGenericProcessorFactory genericProcessorFactory)
         {
             _jsonApiContext = jsonApiContext;
-            _genericProcessorFactory = genericProcessorFactory;
+        }
+
+        public JsonApiDeSerializer(IJsonApiContext jsonApiContext)
+        {
+            _jsonApiContext = jsonApiContext;
         }
 
         public object Deserialize(string requestBody)
@@ -225,10 +232,11 @@ private object SetHasManyRelationship(object entity,
             ContextEntity contextEntity,
             Dictionary<string, RelationshipData> relationships)
         {
-            var entityProperty = entityProperties.FirstOrDefault(p => p.Name == attr.InternalRelationshipName);
+            // TODO: is this necessary? if not, remove
+            // var entityProperty = entityProperties.FirstOrDefault(p => p.Name == attr.InternalRelationshipName);
 
-            if (entityProperty == null)
-                throw new JsonApiException(400, $"{contextEntity.EntityType.Name} does not contain an relationsip named {attr.InternalRelationshipName}");
+            // if (entityProperty == null)
+            //     throw new JsonApiException(400, $"{contextEntity.EntityType.Name} does not contain a relationsip named '{attr.InternalRelationshipName}'");
 
             var relationshipName = attr.PublicRelationshipName;
 
@@ -238,11 +246,16 @@ private object SetHasManyRelationship(object entity,
 
                 if (data == null) return entity;
 
-                var genericProcessor = _genericProcessorFactory.GetProcessor<IGenericProcessor>(typeof(GenericProcessor<>), attr.Type);
+                var resourceRelationships = attr.Type.GetEmptyCollection<IIdentifiable>();
 
-                var ids = relationshipData.ManyData.Select(r => r.Id);
+                var relationshipShells = relationshipData.ManyData.Select(r =>
+                {
+                    var instance = attr.Type.New<IIdentifiable>();
+                    instance.StringId = r.Id;
+                    return instance;
+                });
 
-                genericProcessor.SetRelationships(entity, attr, ids);
+                attr.SetValue(entity, relationshipShells);
             }
 
             return entity;

test/UnitTests/Extensions/TypeExtensions_Tests.cs

@@ -0,0 +1,44 @@
+using JsonApiDotNetCore.Models;
+using Xunit;
+using JsonApiDotNetCore.Extensions;
+using System.Collections.Generic;
+
+namespace UnitTests.Extensions
+{
+    public class TypeExtensions_Tests
+    {
+        [Fact]
+        public void GetCollection_Creates_List_If_T_Implements_Interface()
+        {
+            // arrange
+            var type = typeof(Model);
+
+            // act
+            var collection = type.GetEmptyCollection<IIdentifiable>();
+
+            // assert
+            Assert.NotNull(collection);
+            Assert.Empty(collection);
+            Assert.IsType<List<Model>>(collection);
+        }
+
+        [Fact]
+        public void New_Creates_An_Instance_If_T_Implements_Interface()
+        {
+            // arrange
+            var type = typeof(Model);
+
+            // act
+            var instance = type.New<IIdentifiable>();
+
+            // assert
+            Assert.NotNull(instance);
+            Assert.IsType<Model>(instance);
+        }
+
+        private class Model : IIdentifiable
+        {
+            public string StringId { get; set; }
+        }
+    }
+}