fix(#218): include independent hasOne identifier

in all requests for the dependent side of the relationship by default

Author: jaredcnance

Diff for: src/JsonApiDotNetCore/Builders/DocumentBuilder.cs

@@ -13,9 +13,9 @@ public class DocumentBuilder : IDocumentBuilder
         private readonly IJsonApiContext _jsonApiContext;
         private readonly IContextGraph _contextGraph;
         private readonly IRequestMeta _requestMeta;
-        private readonly DocumentBuilderOptions _documentBuilderOptions; 
+        private readonly DocumentBuilderOptions _documentBuilderOptions;
 
-        public DocumentBuilder(IJsonApiContext jsonApiContext, IRequestMeta requestMeta=null, IDocumentBuilderOptionsProvider documentBuilderOptionsProvider=null)
+        public DocumentBuilder(IJsonApiContext jsonApiContext, IRequestMeta requestMeta = null, IDocumentBuilderOptionsProvider documentBuilderOptionsProvider = null)
         {
             _jsonApiContext = jsonApiContext;
             _contextGraph = jsonApiContext.ContextGraph;
@@ -143,34 +143,42 @@ private bool OmitNullValuedAttribute(AttrAttribute attr, object attributeValue)
         private void AddRelationships(DocumentData data, ContextEntity contextEntity, IIdentifiable entity)
         {
             data.Relationships = new Dictionary<string, RelationshipData>();
+            contextEntity.Relationships.ForEach(r =>
+                data.Relationships.Add(
+                    r.PublicRelationshipName,
+                    GetRelationshipData(r, contextEntity, entity)
+                )
+            );
+        }
+
+        private RelationshipData GetRelationshipData(RelationshipAttribute attr, ContextEntity contextEntity, IIdentifiable entity)
+        {
             var linkBuilder = new LinkBuilder(_jsonApiContext);
 
-            contextEntity.Relationships.ForEach(r =>
+            var relationshipData = new RelationshipData();
+
+            if (attr.DocumentLinks.HasFlag(Link.None) == false)
             {
-                var relationshipData = new RelationshipData();
+                relationshipData.Links = new Links();
+                if (attr.DocumentLinks.HasFlag(Link.Self))
+                    relationshipData.Links.Self = linkBuilder.GetSelfRelationLink(contextEntity.EntityName, entity.StringId, attr.PublicRelationshipName);
 
-                if (r.DocumentLinks.HasFlag(Link.None) == false)
-                {
-                    relationshipData.Links = new Links();
-                    if (r.DocumentLinks.HasFlag(Link.Self))
-                        relationshipData.Links.Self = linkBuilder.GetSelfRelationLink(contextEntity.EntityName, entity.StringId, r.PublicRelationshipName);
+                if (attr.DocumentLinks.HasFlag(Link.Related))
+                    relationshipData.Links.Related = linkBuilder.GetRelatedRelationLink(contextEntity.EntityName, entity.StringId, attr.PublicRelationshipName);
+            }
 
-                    if (r.DocumentLinks.HasFlag(Link.Related))
-                        relationshipData.Links.Related = linkBuilder.GetRelatedRelationLink(contextEntity.EntityName, entity.StringId, r.PublicRelationshipName);
-                }
-                
-                var navigationEntity = _jsonApiContext.ContextGraph
-                    .GetRelationship(entity, r.InternalRelationshipName);
-
-                if (navigationEntity == null)
-                    relationshipData.SingleData = null;
-                else if (navigationEntity is IEnumerable)
-                    relationshipData.ManyData = GetRelationships((IEnumerable<object>)navigationEntity);
-                else
-                    relationshipData.SingleData = GetRelationship(navigationEntity);
-                
-                data.Relationships.Add(r.PublicRelationshipName, relationshipData);
-            });
+            // this only includes the navigation property, we need to actually check the navigation property Id
+            var navigationEntity = _jsonApiContext.ContextGraph.GetRelationship(entity, attr.InternalRelationshipName);
+            if (navigationEntity == null)
+                relationshipData.SingleData = attr.IsHasOne
+                    ? GetIndependentRelationshipIdentifier((HasOneAttribute)attr, entity)
+                    : null;
+            else if (navigationEntity is IEnumerable)
+                relationshipData.ManyData = GetRelationships((IEnumerable<object>)navigationEntity);
+            else
+                relationshipData.SingleData = GetRelationship(navigationEntity);
+
+            return relationshipData;
         }
 
         private List<DocumentData> GetIncludedEntities(List<DocumentData> included, ContextEntity contextEntity, IIdentifiable entity)
@@ -240,23 +248,40 @@ private List<ResourceIdentifierObject> GetRelationships(IEnumerable<object> enti
             var relationships = new List<ResourceIdentifierObject>();
             foreach (var entity in entities)
             {
-                relationships.Add(new ResourceIdentifierObject {
+                relationships.Add(new ResourceIdentifierObject
+                {
                     Type = typeName.EntityName,
                     Id = ((IIdentifiable)entity).StringId
                 });
             }
             return relationships;
         }
+
         private ResourceIdentifierObject GetRelationship(object entity)
         {
             var objType = entity.GetType();
+            var contextEntity = _jsonApiContext.ContextGraph.GetContextEntity(objType);
 
-            var typeName = _jsonApiContext.ContextGraph.GetContextEntity(objType);
-
-            return new ResourceIdentifierObject {
-                Type = typeName.EntityName,
+            return new ResourceIdentifierObject
+            {
+                Type = contextEntity.EntityName,
                 Id = ((IIdentifiable)entity).StringId
             };
         }
+
+        private ResourceIdentifierObject GetIndependentRelationshipIdentifier(HasOneAttribute hasOne, IIdentifiable entity)
+        {
+            var independentRelationshipIdentifier = hasOne.GetIdentifiablePropertyValue(entity);
+            if (independentRelationshipIdentifier == null)
+                return null;
+
+            var relatedContextEntity = _jsonApiContext.ContextGraph.GetContextEntity(hasOne.Type);
+
+            return new ResourceIdentifierObject
+            {
+                Type = relatedContextEntity.EntityName,
+                Id = independentRelationshipIdentifier.ToString()
+            };
+        }
     }
 }

Diff for: src/JsonApiDotNetCore/Models/HasOneAttribute.cs

@@ -2,21 +2,61 @@ namespace JsonApiDotNetCore.Models
 {
     public class HasOneAttribute : RelationshipAttribute
     {
-        public HasOneAttribute(string publicName, Link documentLinks = Link.All, bool canInclude = true)
+        /// <summary>
+        /// Create a HasOne relational link to another entity
+        /// </summary>
+        /// 
+        /// <param name="publicName">The relationship name as exposed by the API</param>
+        /// <param name="documentLinks">Which links are available. Defaults to <see cref="Link.All"/></param>
+        /// <param name="canInclude">Whether or not this relationship can be included using the <c>?include=public-name</c> query string</param>
+        /// <param name="withForiegnKey">The foreign key property name. Defaults to <c>"{RelationshipName}Id"</c></param>
+        /// 
+        /// <example>
+        /// Using an alternative foreign key:
+        /// 
+        /// <code>
+        /// public class Article : Identifiable 
+        /// {
+        ///     [HasOne("author", withForiegnKey: nameof(AuthorKey)]
+        ///     public Author Author { get; set; }
+        ///     public int AuthorKey { get; set; }
+        /// }
+        /// </code>
+        /// 
+        /// </example>
+        public HasOneAttribute(string publicName, Link documentLinks = Link.All, bool canInclude = true, string withForiegnKey = null)
         : base(publicName, documentLinks, canInclude)
-        { }
+        {
+            _explicitIdentifiablePropertyName = withForiegnKey;
+        }
+
+        private readonly string _explicitIdentifiablePropertyName;
+
+        /// <summary>
+        /// The independent entity identifier.
+        /// </summary>
+        public string IdentifiablePropertyName => string.IsNullOrWhiteSpace(_explicitIdentifiablePropertyName)
+            ? $"{InternalRelationshipName}Id"
+            : _explicitIdentifiablePropertyName;
 
         public override void SetValue(object entity, object newValue)
         {
-            var propertyName = (newValue.GetType() == Type) 
-                ? InternalRelationshipName 
-                : $"{InternalRelationshipName}Id";
-                
+            var propertyName = (newValue.GetType() == Type)
+                ? InternalRelationshipName
+                : IdentifiablePropertyName;
+
             var propertyInfo = entity
                 .GetType()
                 .GetProperty(propertyName);
-            
+
             propertyInfo.SetValue(entity, newValue);
         }
+
+        // HACK: this will likely require boxing
+        // we should be able to move some of the reflection into the ContextGraphBuilder
+        internal object GetIdentifiablePropertyValue(object entity) => entity
+                .GetType()
+                .GetProperty(IdentifiablePropertyName)
+                .GetValue(entity);
     }
 }

Diff for: src/JsonApiDotNetCore/Serialization/JsonApiDeSerializer.cs

@@ -175,7 +175,7 @@ private object SetRelationships(
             foreach (var attr in contextEntity.Relationships)
             {
                 entity = attr.IsHasOne
-                    ? SetHasOneRelationship(entity, entityProperties, attr, contextEntity, relationships)
+                    ? SetHasOneRelationship(entity, entityProperties, (HasOneAttribute)attr, contextEntity, relationships)
                     : SetHasManyRelationship(entity, entityProperties, attr, contextEntity, relationships);
             }
 
@@ -184,7 +184,7 @@ private object SetRelationships(
 
         private object SetHasOneRelationship(object entity,
             PropertyInfo[] entityProperties,
-            RelationshipAttribute attr,
+            HasOneAttribute attr,
             ContextEntity contextEntity,
             Dictionary<string, RelationshipData> relationships)
         {
@@ -204,7 +204,7 @@ private object SetHasOneRelationship(object entity,
 
                 var newValue = rio.Id;
 
-                var foreignKey = attr.InternalRelationshipName + "Id";
+                var foreignKey = attr.IdentifiablePropertyName;
                 var entityProperty = entityProperties.FirstOrDefault(p => p.Name == foreignKey);
                 if (entityProperty == null)
                     throw new JsonApiException(400, $"{contextEntity.EntityType.Name} does not contain a foreign key property '{foreignKey}' for has one relationship '{attr.InternalRelationshipName}'");

Diff for: test/UnitTests/Builders/DocumentBuilder_Tests.cs

@@ -145,6 +145,35 @@ public void Related_Data_Included_In_Relationships_By_Default()
             // act
             var document = documentBuilder.Build(entity);
 
+            // assert
+            var relationshipData = document.Data.Relationships[relationshipName];
+            Assert.NotNull(relationshipData);
+            Assert.NotNull(relationshipData.SingleData);
+            Assert.NotNull(relationshipData.SingleData);
+            Assert.Equal(relatedId.ToString(), relationshipData.SingleData.Id);
+            Assert.Equal(relatedTypeName, relationshipData.SingleData.Type);
+        }
+
+        [Fact]
+        public void IndependentIdentifier__Included_In_HasOne_Relationships_By_Default()
+        {
+            // arrange
+            const string relatedTypeName = "related-models";
+            const string relationshipName = "related-model";
+            const int relatedId = 1;
+            _jsonApiContextMock
+                .Setup(m => m.ContextGraph)
+                .Returns(_options.ContextGraph);
+
+            var documentBuilder = new DocumentBuilder(_jsonApiContextMock.Object);
+            var entity = new Model
+            {
+                RelatedModelId = relatedId
+            };
+
+            // act
+            var document = documentBuilder.Build(entity);
+
             // assert
             var relationshipData = document.Data.Relationships[relationshipName];
             Assert.NotNull(relationshipData);