set new HasManyRelationships with EntityState.Unchanged

Author: jaredcnance

src/JsonApiDotNetCore/Data/DefaultEntityRepository.cs

@@ -85,10 +85,29 @@ public virtual async Task<TEntity> GetAndIncludeAsync(TId id, string relationshi
         public virtual async Task<TEntity> CreateAsync(TEntity entity)
         {
             _dbSet.Add(entity);
+
+            DetachHasManyPointers();
+
             await _context.SaveChangesAsync();
             return entity;
         }
 
+        /// <summary>
+        /// This is used to allow creation of HasMany relationships when the
+        /// dependent side of the relationship already exists.
+        /// </summary>
+        private void DetachHasManyPointers()
+        {
+            var relationships = _jsonApiContext.HasManyRelationshipPointers.Get();
+            foreach(var relationship in relationships)
+            {
+                foreach(var pointer in relationship.Value)
+                {
+                    _context.Entry(pointer).State = EntityState.Unchanged;
+                }
+            }
+        }
+
         public virtual async Task<TEntity> UpdateAsync(TId id, TEntity entity)
         {
             var oldEntity = await GetAsync(id);

src/JsonApiDotNetCore/Data/IEntityRepository.cs

@@ -1,7 +1,3 @@
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
-using JsonApiDotNetCore.Internal.Query;
 using JsonApiDotNetCore.Models;
 
 namespace JsonApiDotNetCore.Data

src/JsonApiDotNetCore/Extensions/DbContextExtensions.cs

@@ -1,20 +1,12 @@
-using Microsoft.EntityFrameworkCore;
 using System;
+using Microsoft.EntityFrameworkCore;
 
 namespace JsonApiDotNetCore.Extensions
 {
     public static class DbContextExtensions
     {
-        public static DbSet<T> GetDbSet<T>(this DbContext context) where T : class
-        {
-            var contextProperties = context.GetType().GetProperties();
-            foreach(var property in contextProperties)
-            {
-                if (property.PropertyType == typeof(DbSet<T>))
-                    return (DbSet<T>)property.GetValue(context);
-            }
-
-            throw new ArgumentException($"DbSet of type {typeof(T).FullName} not found on the DbContext", nameof(T));
-        }
+        [Obsolete("This is no longer required since the introduction of context.Set<T>", error: false)]
+        public static DbSet<T> GetDbSet<T>(this DbContext context) where T : class 
+            => context.Set<T>();
     }
 }

src/JsonApiDotNetCore/Request/HasManyRelationshipPointers.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace JsonApiDotNetCore.Request
+{
+    /// <summary>
+    /// Stores information to set relationships for the request resource. 
+    /// These relationships must already exist and should not be re-created.
+    /// 
+    /// The expected use case is POST-ing or PATCH-ing 
+    /// an entity with HasMany relaitonships:
+    /// <code>
+    /// {
+    ///    "data": {
+    ///      "type": "photos",
+    ///      "attributes": {
+    ///        "title": "Ember Hamster",
+    ///        "src": "http://example.com/images/productivity.png"
+    ///      },
+    ///      "relationships": {
+    ///        "tags": {
+    ///          "data": [
+    ///            { "type": "tags", "id": "2" },
+    ///            { "type": "tags", "id": "3" }
+    ///          ]
+    ///        }
+    ///      }
+    ///    }
+    ///  }
+    /// </code>
+    /// </summary>
+    public class HasManyRelationshipPointers
+    {
+        private Dictionary<Type, IList> _hasManyRelationships = new Dictionary<Type, IList>();
+
+        /// <summary>
+        /// Add the relationship to the list of relationships that should be 
+        /// set in the repository layer.
+        /// </summary>
+        public void Add(Type dependentType, IList entities)
+            => _hasManyRelationships[dependentType] = entities;
+
+        /// <summary>
+        /// Get all the models that should be associated
+        /// </summary>
+        public Dictionary<Type, IList> Get() => _hasManyRelationships;
+    }
+}

src/JsonApiDotNetCore/Serialization/JsonApiDeSerializer.cs

@@ -232,12 +232,6 @@ private object SetHasManyRelationship(object entity,
             ContextEntity contextEntity,
             Dictionary<string, RelationshipData> relationships)
         {
-            // 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 a relationsip named '{attr.InternalRelationshipName}'");
-
             var relationshipName = attr.PublicRelationshipName;
 
             if (relationships.TryGetValue(relationshipName, out RelationshipData relationshipData))
@@ -255,9 +249,9 @@ private object SetHasManyRelationship(object entity,
 
                 var convertedCollection = TypeHelper.ConvertCollection(relationshipShells, attr.Type);
 
-                // var convertedCollection = TypeHelper.ConvertCollection(relationshipShells, attr.Type);
-
                 attr.SetValue(entity, convertedCollection);
+
+                _jsonApiContext.HasManyRelationshipPointers.Add(attr.Type, convertedCollection);
             }
 
             return entity;

src/JsonApiDotNetCore/Services/IJsonApiContext.cs

@@ -6,6 +6,7 @@
 using JsonApiDotNetCore.Internal.Generics;
 using JsonApiDotNetCore.Internal.Query;
 using JsonApiDotNetCore.Models;
+using JsonApiDotNetCore.Request;
 
 namespace JsonApiDotNetCore.Services
 {
@@ -28,6 +29,7 @@ public interface IJsonApiContext
         Type ControllerType { get; set; }
         Dictionary<string, object> DocumentMeta { get; set; }
         bool IsBulkOperationRequest { get; set; }
+        HasManyRelationshipPointers HasManyRelationshipPointers { get; }
 
         TAttribute GetControllerAttribute<TAttribute>() where TAttribute : Attribute;
     }

src/JsonApiDotNetCore/Services/JsonApiContext.cs

@@ -1,12 +1,12 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using JsonApiDotNetCore.Builders;
 using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.Internal;
 using JsonApiDotNetCore.Internal.Generics;
 using JsonApiDotNetCore.Internal.Query;
 using JsonApiDotNetCore.Models;
+using JsonApiDotNetCore.Request;
 using Microsoft.AspNetCore.Http;
 
 namespace JsonApiDotNetCore.Services
@@ -52,6 +52,7 @@ public JsonApiContext(
         public Type ControllerType { get; set; }
         public Dictionary<string, object> DocumentMeta { get; set; }
         public bool IsBulkOperationRequest { get; set; }
+        public HasManyRelationshipPointers HasManyRelationshipPointers { get; } = new HasManyRelationshipPointers();
 
         public IJsonApiContext ApplyContext<T>(object controller)
         {