feat(*): implement fetching relationships

Author: jaredcnance

src/JsonApiDotNetCore/Builders/DocumentBuilder.cs

@@ -52,11 +52,15 @@ private DocumentData _getData(ContextEntity contextEntity, IIdentifiable entity)
             var data = new DocumentData
             {
                 Type = contextEntity.EntityName,
-                Id = entity.Id.ToString(),
-                Attributes = new Dictionary<string, object>(),
-                Relationships = new Dictionary<string, Dictionary<string, object>>()
+                Id = entity.Id.ToString()
             };
 
+            if(_jsonApiContext.IsRelationshipData)
+                return data;
+
+            data.Attributes = new Dictionary<string, object>();
+            data.Relationships = new Dictionary<string, Dictionary<string, object>>();
+
             contextEntity.Attributes.ForEach(attr =>
             {
                 data.Attributes.Add(attr.PublicAttributeName, attr.GetValue(entity));

src/JsonApiDotNetCore/Controllers/JsonApiController.cs

@@ -70,6 +70,14 @@ public virtual async Task<IActionResult> GetAsync(TId id)
             return Ok(entity);
         }
 
+        [HttpGet("{id}/relationships/{relationshipName}")]
+        public virtual async Task<IActionResult> GetRelationshipsAsync(TId id, string relationshipName)
+        {
+            _jsonApiContext.IsRelationshipData = true;
+
+            return await GetRelationshipAsync(id, relationshipName);
+        }
+
         [HttpGet("{id}/{relationshipName}")]
         public virtual async Task<IActionResult> GetRelationshipAsync(TId id, string relationshipName)
         {

src/JsonApiDotNetCore/Extensions/ServiceProviderExtensions.cs

@@ -31,7 +31,7 @@ public static void AddJsonApiInternals<TContext>(this IServiceCollection service
             services.AddScoped(typeof(IEntityRepository<,>), typeof(DefaultEntityRepository<,>));
 
             services.AddSingleton<IContextGraph>(contextGraph);
-            services.AddSingleton<IJsonApiContext,JsonApiContext>();
+            services.AddScoped<IJsonApiContext,JsonApiContext>();
             services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
 
             services.AddScoped<JsonApiRouteHandler>();

src/JsonApiDotNetCore/Serialization/JsonApiSerializer.cs

@@ -18,18 +18,19 @@ public static string Serialize(object entity, IJsonApiContext jsonApiContext)
         private static string _serializeDocuments(object entity, IJsonApiContext jsonApiContext)
         {
             var documentBuilder = new DocumentBuilder(jsonApiContext);
-
             var entities = entity as IEnumerable<IIdentifiable>;
             var documents = documentBuilder.Build(entities);
             return JsonConvert.SerializeObject(documents);
         }
 
-         private static string _serializeDocument(object entity, IJsonApiContext jsonApiContext)
+        private static string _serializeDocument(object entity, IJsonApiContext jsonApiContext)
         {
             var documentBuilder = new DocumentBuilder(jsonApiContext);
             var identifiableEntity = entity as IIdentifiable;
             var document = documentBuilder.Build(identifiableEntity);
-            return JsonConvert.SerializeObject(document);
+            return JsonConvert.SerializeObject(document, new JsonSerializerSettings {
+                NullValueHandling = NullValueHandling.Ignore
+            });
         }
     }
 }

src/JsonApiDotNetCore/Services/IJsonApiContext.cs

@@ -10,5 +10,6 @@ public interface IJsonApiContext
         ContextEntity RequestEntity { get; set; }
         string BasePath { get; set; }
         IQueryCollection Query { get; set; }
+        bool IsRelationshipData { get; set; }
     }
 }

src/JsonApiDotNetCore/Services/JsonApiContext.cs

@@ -19,6 +19,7 @@ public JsonApiContext(
         public ContextEntity RequestEntity { get; set; }
         public string BasePath { get; set; }
         public IQueryCollection Query { get; set; }
+        public bool IsRelationshipData { get; set; }
 
         public IJsonApiContext ApplyContext<T>()
         {

src/JsonApiDotNetCoreExample/README.md

@@ -8,6 +8,7 @@
 - [x] Add support for authorization/context-scoping middleware
 - [x] Filtering
 - [x] Sorting
+- [x] Fetching relationships
 - [ ] Creating relationships
 - [ ] Include Entities
 - [ ] BadRequest should be 422 in POST