Fix/patch relationships

src/JsonApiDotNetCore/Data/DefaultEntityRepository.cs

@@ -105,9 +105,12 @@ public virtual async Task<TEntity> UpdateAsync(TId id, TEntity entity)
                 attr.SetValue(oldEntity, attr.GetValue(entity));
             });
 
+            foreach(var relationship in _jsonApiContext.RelationshipsToUpdate)
+                relationship.Key.SetValue(oldEntity, relationship.Value);
+
             await _context.SaveChangesAsync();
 
-        return oldEntity;
+            return oldEntity;
         }
 
         public async Task UpdateRelationshipsAsync(object parent, RelationshipAttribute relationship, IEnumerable<string> relationshipIds)

src/JsonApiDotNetCore/Models/HasManyAttribute.cs

@@ -1,4 +1,4 @@
-using System;
+using System.Reflection;
 
 namespace JsonApiDotNetCore.Models
 {
@@ -9,5 +9,14 @@ public HasManyAttribute(string publicName)
         {
             PublicRelationshipName = publicName;
         }
+
+        public override void SetValue(object entity, object newValue)
+        {
+            var propertyInfo = entity
+                .GetType()
+                .GetProperty(InternalRelationshipName);
+
+            propertyInfo.SetValue(entity, newValue);        
+        }
     }
 }

src/JsonApiDotNetCore/Models/HasOneAttribute.cs

@@ -1,3 +1,5 @@
+using System.Reflection;
+
 namespace JsonApiDotNetCore.Models
 {
     public class HasOneAttribute : RelationshipAttribute
@@ -7,5 +9,18 @@ public HasOneAttribute(string publicName)
         {
             PublicRelationshipName = publicName;
         }
+
+        public override void SetValue(object entity, object newValue)
+        {
+            var propertyName = (newValue.GetType() == Type) 
+                ? InternalRelationshipName 
+                : $"{InternalRelationshipName}Id";
+
+            var propertyInfo = entity
+                .GetType()
+                .GetProperty(propertyName);
+
+            propertyInfo.SetValue(entity, newValue);
+        }
     }
 }

src/JsonApiDotNetCore/Models/RelationshipAttribute.cs

@@ -1,9 +1,8 @@
 using System;
-using System.Reflection;
 
 namespace JsonApiDotNetCore.Models
 {
-    public class RelationshipAttribute : Attribute
+    public abstract class RelationshipAttribute : Attribute
     {
         protected RelationshipAttribute(string publicName)
         {
@@ -16,13 +15,6 @@ protected RelationshipAttribute(string publicName)
         public bool IsHasMany { get { return this.GetType() == typeof(HasManyAttribute); } }
         public bool IsHasOne { get { return this.GetType() == typeof(HasOneAttribute); } }
 
-        public void SetValue(object entity, object newValue)
-        {
-            var propertyInfo = entity
-                .GetType()
-                .GetProperty(InternalRelationshipName);
-
-            propertyInfo.SetValue(entity, newValue);        
-        }
+        public abstract void SetValue(object entity, object newValue);
     }
 }

src/JsonApiDotNetCore/Serialization/JsonApiDeSerializer.cs

@@ -141,12 +141,18 @@ private object _setHasOneRelationship(object entity,
 
             if (relationships.TryGetValue(relationshipName, out RelationshipData relationshipData))
             {
+                var relationshipAttr = _jsonApiContext.RequestEntity.Relationships
+                        .SingleOrDefault(r => r.PublicRelationshipName == relationshipName);
+
                 var data = (Dictionary<string, string>)relationshipData.ExposedData;
 
                 if (data == null) return entity;
 
                 var newValue = data["id"];
                 var convertedValue = TypeHelper.ConvertType(newValue, entityProperty.PropertyType);
+
+                _jsonApiContext.RelationshipsToUpdate[relationshipAttr] = convertedValue;
+
                 entityProperty.SetValue(entity, convertedValue);
             }
 

src/JsonApiDotNetCore/Services/IJsonApiContext.cs

@@ -3,6 +3,7 @@
 using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Internal;
 using JsonApiDotNetCore.Internal.Query;
+using JsonApiDotNetCore.Models;
 
 namespace JsonApiDotNetCore.Services
 {
@@ -20,5 +21,6 @@ public interface IJsonApiContext
         PageManager PageManager { get; set; }
         IMetaBuilder MetaBuilder { get; set; }
         IGenericProcessorFactory GenericProcessorFactory { get; set; }
+        Dictionary<RelationshipAttribute, object> RelationshipsToUpdate { get; set; }
     }
 }

src/JsonApiDotNetCore/Services/JsonApiContext.cs

@@ -4,6 +4,7 @@
 using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Internal;
 using JsonApiDotNetCore.Internal.Query;
+using JsonApiDotNetCore.Models;
 using Microsoft.AspNetCore.Http;
 
 namespace JsonApiDotNetCore.Services
@@ -23,6 +24,7 @@ public JsonApiContext(
             Options = options;
             MetaBuilder = metaBuilder;
             GenericProcessorFactory = genericProcessorFactory;
+            RelationshipsToUpdate = new Dictionary<RelationshipAttribute, object>();
         }
 
         public JsonApiOptions Options { get; set; }
@@ -36,6 +38,7 @@ public JsonApiContext(
         public PageManager PageManager { get; set; }
         public IMetaBuilder MetaBuilder { get; set; }
         public IGenericProcessorFactory GenericProcessorFactory { get; set; }
+        public Dictionary<RelationshipAttribute, object> RelationshipsToUpdate { get; set; }
 
         public IJsonApiContext ApplyContext<T>()
         {

test/JsonApiDotNetCoreExampleTests/Acceptance/Spec/UpdatingDataTests.cs

@@ -1,4 +1,3 @@
-using System.Collections.Generic;
 using System.Linq;
 using System.Net;
 using System.Net.Http;
@@ -7,15 +6,15 @@
 using Bogus;
 using DotNetCoreDocs;
 using DotNetCoreDocs.Writers;
-using JsonApiDotNetCore.Serialization;
-using JsonApiDotNetCore.Services;
 using JsonApiDotNetCoreExample;
 using JsonApiDotNetCoreExample.Data;
 using JsonApiDotNetCoreExample.Models;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.EntityFrameworkCore;
 using Newtonsoft.Json;
 using Xunit;
+using Person = JsonApiDotNetCoreExample.Models.Person;
 
 namespace JsonApiDotNetCoreExampleTests.Acceptance.Spec
 {
@@ -25,14 +24,18 @@ public class UpdatingDataTests
         private DocsFixture<Startup, JsonDocWriter> _fixture;
         private AppDbContext _context;
         private Faker<TodoItem> _todoItemFaker;
+        private Faker<Person> _personFaker;
 
         public UpdatingDataTests(DocsFixture<Startup, JsonDocWriter> fixture)
         {
             _fixture = fixture;
             _context = fixture.GetService<AppDbContext>();
-             _todoItemFaker = new Faker<TodoItem>()
+            _todoItemFaker = new Faker<TodoItem>()
                 .RuleFor(t => t.Description, f => f.Lorem.Sentence())
                 .RuleFor(t => t.Ordinal, f => f.Random.Number());
+            _personFaker = new Faker<Person>()
+                .RuleFor(p => p.FirstName, f => f.Name.FirstName())
+                .RuleFor(p => p.LastName, f => f.Name.LastName());
         }
 
         [Fact]
@@ -73,5 +76,62 @@ public async Task Respond_404_If_EntityDoesNotExist()
             // Assert
             Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
         }
+
+        [Fact]
+        public async Task Can_Patch_Entity_And_HasOne_Relationships()
+        {
+            // arrange
+            var todoItem = _todoItemFaker.Generate();
+            var person = _personFaker.Generate();
+            _context.TodoItems.Add(todoItem);
+            _context.People.Add(person);
+            _context.SaveChanges();
+
+            var builder = new WebHostBuilder()
+                .UseStartup<Startup>();
+            var server = new TestServer(builder);
+            var client = server.CreateClient();
+
+            var content = new
+            {
+                data = new
+                {
+                    type = "todo-items",
+                    attributes = new
+                    {
+                        description = todoItem.Description,
+                        ordinal = todoItem.Ordinal
+                    },
+                    relationships = new
+                    {
+                        owner = new
+                        {
+                            data = new
+                            {
+                                type = "people",
+                                id = person.Id.ToString()
+                            }
+                        }
+                    }
+                }
+            };
+
+            var httpMethod = new HttpMethod("PATCH");
+            var route = $"/api/v1/todo-items/{todoItem.Id}";
+            var request = new HttpRequestMessage(httpMethod, route);
+
+            request.Content = new StringContent(JsonConvert.SerializeObject(content));
+            request.Content.Headers.ContentType = new MediaTypeHeaderValue("application/vnd.api+json");
+
+            // Act
+            var response = await client.SendAsync(request);
+            var updatedTodoItem = _context.TodoItems.AsNoTracking()
+                .Include(t => t.Owner)
+                .SingleOrDefault(t => t.Id == todoItem.Id);
+
+            // Assert
+            Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+            Assert.Equal(person.Id, updatedTodoItem.OwnerId);
+        }
     }
 }