fix: traversal bug related to parsing next layer relationships when layer count > 2

Author: maurei

src/JsonApiDotNetCore/Extensions/IQueryableExtensions.cs

@@ -430,5 +430,13 @@ public static IQueryable<T> PageForward<T>(this IQueryable<T> source, int pageSi
             return source;
         }
 
+        public static void ForEach<T>(this IEnumerable<T> enumeration, Action<T> action)
+        {
+            foreach (T item in enumeration)
+            {
+                action(item);
+            }
+        }
+
     }
 }

src/JsonApiDotNetCore/Hooks/Traversal/TraversalHelper.cs

@@ -55,6 +55,7 @@ public TraversalHelper(
         public RootNode<TEntity> CreateRootNode<TEntity>(IEnumerable<TEntity> rootEntities) where TEntity : class, IIdentifiable
         {
             _processedEntities = new Dictionary<DependentType, HashSet<IIdentifiable>>();
+            RegisterRelationshipProxies(typeof(TEntity));
             var uniqueEntities = ProcessEntities(rootEntities);
             var relationshipsToNextLayer = GetRelationships(typeof(TEntity));
             return new RootNode<TEntity>(uniqueEntities, relationshipsToNextLayer);
@@ -94,7 +95,7 @@ public EntityChildLayer CreateNextLayer(IEnumerable<IEntityNode> nodes)
                     return CreateRelationsipGroupInstance(nextNodeType, proxy, grouped.Value, principals[proxy]);
                 }).ToList();
 
-
+                RegisterRelationshipProxies(nextNodeType);
                 return CreateNodeInstance(nextNodeType, GetRelationships(nextNodeType), relationshipsToPreviousLayer);
             }).ToList();
 
@@ -118,6 +119,8 @@ Dictionary<DependentType, List<KeyValuePair<RelationshipProxy, List<IIdentifiabl
             var principalsGrouped = new Dictionary<RelationshipProxy, List<IIdentifiable>>();
             var dependentsGrouped = new Dictionary<RelationshipProxy, List<IIdentifiable>>();
 
+            principalNodes.ForEach(n => RegisterRelationshipProxies(n.EntityType));
+
             foreach (var node in principalNodes)
             {
                 var principalEntities = node.UniqueEntities;
@@ -181,7 +184,11 @@ HashSet<TEntity> ProcessEntities<TEntity>(IEnumerable<TEntity> incomingEntities)
             Type type = typeof(TEntity);
             var newEntities = UniqueInTree(incomingEntities, type);
             RegisterProcessedEntities(newEntities, type);
+            return newEntities;
+        }
 
+        void RegisterRelationshipProxies(DependentType type)
+        {
             var contextEntity = _graph.GetContextEntity(type);
             foreach (RelationshipAttribute attr in contextEntity.Relationships)
             {
@@ -194,7 +201,6 @@ HashSet<TEntity> ProcessEntities<TEntity>(IEnumerable<TEntity> incomingEntities)
                     RelationshipProxies[attr] = proxy;
                 }
             }
-            return newEntities;
         }
 
 

src/JsonApiDotNetCore/Models/RelationshipAttribute.cs

@@ -99,7 +99,9 @@ public override bool Equals(object obj)
             {
                 return false;
             }
-            return IsHasMany == attr.IsHasMany && PublicRelationshipName.Equals(attr.PublicRelationshipName);
+            bool equalRelationshipName = PublicRelationshipName.Equals(attr.PublicRelationshipName);
+            bool equalPrincipalType = PrincipalType.Equals(attr.PrincipalType);
+            return IsHasMany == attr.IsHasMany && equalRelationshipName && equalPrincipalType;
         }
 
         /// <summary>