Fix Writing Delta Responses

-only write properties in deltaset items that have been set
-support writing additional properties for deleted entities
-nested resource sets that aren't deltasets should be written w/o @delta
-factored out ODataDeletedResourceSerializer
-support writing delta payloads w/out knowing navigation source (i.e., when serializing results from a function)

Author: mikepizzo

src/Microsoft.AspNetCore.OData/Formatter/Serialization/ODataDeletedResourceSerializer.cs

@@ -8,6 +8,7 @@
 using System;
 using System.Collections;
 using System.Diagnostics.Contracts;
+using System.Reflection;
 using System.Runtime.Serialization;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.OData.Abstracts;
@@ -56,10 +57,6 @@ public override async Task WriteObjectAsync(object graph, Type type, ODataMessag
         }
 
         IEdmEntitySetBase entitySet = writeContext.NavigationSource as IEdmEntitySetBase;
-        if (entitySet == null)
-        {
-            throw new SerializationException(SRResources.EntitySetMissingDuringSerialization);
-        }
 
         IEdmTypeReference feedType = writeContext.GetEdmType(graph, type);
         Contract.Assert(feedType != null);
@@ -162,11 +159,19 @@ private async Task WriteDeltaResourceSetAsync(IEnumerable enumerable, IEdmTypeRe
                 }
 
                 lastResource = item;
-                DeltaItemKind kind = GetDelteItemKind(item);
+                DeltaItemKind kind = GetDeltaItemKind(item);
                 switch (kind)
                 {
                     case DeltaItemKind.DeletedResource:
-                        await WriteDeltaDeletedResourceAsync(item, writer, writeContext).ConfigureAwait(false);
+                        // hack. if the WriteDeltaDeletedResourceAsync isn't overridden, call the new version
+                        if (WriteDeltaDeletedResourceAsyncIsOverridden())
+                        {
+                            await WriteDeltaDeletedResourceAsync(item, writer, writeContext).ConfigureAwait(false);
+                        }
+                        else
+                        {
+                            await WriteDeletedResourceAsync(item, elementType, writer, writeContext).ConfigureAwait(false);
+                        }
                         break;
                     case DeltaItemKind.DeltaDeletedLink:
                         await WriteDeltaDeletedLinkAsync(item, writer, writeContext).ConfigureAwait(false);
@@ -212,7 +217,7 @@ await entrySerializer.WriteDeltaObjectInlineAsync(item, elementType, writer, wri
     /// <param name="writeContext">The serializer context.</param>
     /// <returns>The function that generates the NextLink from an object.</returns>
     /// <returns></returns>
-    internal static Func<object, Uri> GetNextLinkGenerator(ODataDeltaResourceSet deltaResourceSet, IEnumerable enumerable, ODataSerializerContext writeContext)
+    internal static Func<object, Uri> GetNextLinkGenerator(ODataResourceSetBase deltaResourceSet, IEnumerable enumerable, ODataSerializerContext writeContext)
     {
         return ODataResourceSetSerializer.GetNextLinkGenerator(deltaResourceSet, enumerable, writeContext);
     }
@@ -266,6 +271,8 @@ public virtual ODataDeltaResourceSet CreateODataDeltaResourceSet(IEnumerable fee
     /// <param name="value">The object to be written.</param>
     /// <param name="writer">The <see cref="ODataDeltaWriter" /> to be used for writing.</param>
     /// <param name="writeContext">The <see cref="ODataSerializerContext"/>.</param>
+    [Obsolete("WriteDeltaDeletedResourceAsync(object, ODataWriter, ODataSerializerContext) is Deprecated and will be removed in the next version." +
+        "Please use WriteDeletedResourceAsync(object, IEdmEntityTypeReference, ODataWriter, ODataSerializerContext)")]
     public virtual async Task WriteDeltaDeletedResourceAsync(object value, ODataWriter writer, ODataSerializerContext writeContext)
     {
         if (writer == null)
@@ -304,6 +311,27 @@ public virtual async Task WriteDeltaDeletedResourceAsync(object value, ODataWrit
         }
     }
 
+    /// <summary>
+    /// Writes the given deltaDeletedEntry specified by the parameter graph as a part of an existing OData message using the given
+    /// messageWriter and the writeContext.
+    /// </summary>
+    /// <param name="value">The object to be written.</param>
+    /// <param name="expectedType">The expected type of the deleted resource.</param>
+    /// <param name="writer">The <see cref="ODataDeltaWriter" /> to be used for writing.</param>
+    /// <param name="writeContext">The <see cref="ODataSerializerContext"/>.</param>
+    public virtual async Task WriteDeletedResourceAsync(object value, IEdmStructuredTypeReference expectedType, ODataWriter writer, ODataSerializerContext writeContext)
+    {
+        if (writer == null)
+        {
+            throw Error.ArgumentNull(nameof(writer));
+        }
+
+        //todo:use serializer provider
+        ODataDeletedResourceSerializer deletedResourceSerializer = new ODataDeletedResourceSerializer(SerializerProvider);
+
+        await deletedResourceSerializer.WriteObjectInlineAsync(value, expectedType, writer, writeContext);
+    }
+
     /// <summary>
     /// Writes the given deltaDeletedLink specified by the parameter graph as a part of an existing OData message using the given
     /// messageWriter and the writeContext.
@@ -382,7 +410,7 @@ public virtual async Task WriteDeltaLinkAsync(object value, ODataWriter writer,
         }
     }
 
-    internal DeltaItemKind GetDelteItemKind(object item)
+    internal DeltaItemKind GetDeltaItemKind(object item)
     {
         IEdmChangedObject edmChangedObject = item as IEdmChangedObject;
         if (edmChangedObject != null)
@@ -414,4 +442,11 @@ private static IEdmStructuredTypeReference GetResourceType(IEdmTypeReference fee
         string message = Error.Format(SRResources.CannotWriteType, typeof(ODataDeltaResourceSetSerializer).Name, feedType.FullName());
         throw new SerializationException(message);
     }
+
+    private bool WriteDeltaDeletedResourceAsyncIsOverridden()
+    {
+        MethodInfo method = GetType().GetMethod("WriteDeltaDeletedResourceAsync", new Type[] { typeof(object), typeof(ODataWriter), typeof(ODataSerializerContext) });
+        Contract.Assert(method != null, "WriteDeltaDeletedResourceAsync is not defined.");
+        return method.DeclaringType != typeof(ODataDeltaResourceSetSerializer);
+    }
 }