Fix empty serializable members with packer/unpacker interfaces should be serialized. #202

This commit add
* Unit tests for new specs.
* Relaxes validation to allow types which implement I[Un][Async]Packable fully but have no members.
* Add additional validation to check such types implements pair of interfaces or not.

Author: yfakariya

CHANGES.txt

@@ -619,7 +619,7 @@ Release 0.9.0 beta1 2016/09/24
   BUG FIXES
   * Fix nuspec to prevent old NuGet clients which do not support .NET Standard TFMs. Issue #177.
 
-Release 0.9.0 (planned)
+Release 0.9.0 beta2 2017/2/11
 
   BREAKING CHANGES
   * MessagePackObject comparison which have large binary data will be about 2x - 18x slower in .NET 3.5/4.5/4.6(other platforms will not be affected).
@@ -641,4 +641,4 @@ Release 0.9.0 (planned)
   * Fix Windows Native build error. Issue #206.
   * Fix built-in collection serializers such as List<T> serializer causes SecurityException when the program run in restricted environment like Silverlight. Issue #205.
   * Fix null items of complex type in List<T> or Dictionary<TKey, TValue> will not be deserialized as null. Issue #211. (from 0.8.1)
-
+  * Fix types which implement IPackable and IUnpackable but do not have any members cannot be serialized. Issue #202

src/MsgPack/Serialization/AbstractSerializers/SerializerBuilder`2.Object.cs

@@ -28,6 +28,7 @@
 using System.Globalization;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.Serialization;
 #if FEATURE_TAP
 using System.Threading;
 using System.Threading.Tasks;
@@ -168,6 +169,19 @@ private TConstruct BuildIPackablePackToCore( TContext context, Type @interface )
 
 		private void BuildObjectPackTo( TContext context, SerializationTarget targetInfo, bool isAsync )
 		{
+			if ( targetInfo.Members.Count == 0 )
+			{
+				throw new SerializationException(
+					String.Format(
+						CultureInfo.CurrentCulture,
+						isAsync
+						? "At least one serializable member is required because type '{0}' does not implement IAsyncPackable interface."
+						: "At least one serializable member is required because type '{0}' does not implement IPackable interface.",
+						this.TargetType
+					)
+				);
+			}
+
 			var methodName = 
 #if FEATURE_TAP
 				isAsync ? MethodName.PackToAsyncCore : 
@@ -758,6 +772,19 @@ private IEnumerable<TConstruct> BuildIUnpackableUnpackFromCore( TContext context
 
 		private void BuildObjectUnpackFrom( TContext context, SerializationTarget targetInfo, bool isAsync )
 		{
+			if ( targetInfo.Members.Count == 0 )
+			{
+				throw new SerializationException(
+					String.Format(
+						CultureInfo.CurrentCulture,
+						isAsync
+						? "At least one serializable member is required because type '{0}' does not implement IAsyncUnpackable interface."
+						: "At least one serializable member is required because type '{0}' does not implement IUnpackable interface.",
+						this.TargetType
+					)
+				);
+			}
+
 			/*
 			 *	#if T is IUnpackable
 			 *  result.UnpackFromMessage( unpacker );

src/MsgPack/Serialization/CodeDomSerializers/CodeDomContext.cs

@@ -32,7 +32,6 @@
 using System.Linq;
 using System.Reflection;
 using System.Security;
-using System.Text;
 #if FEATURE_TAP
 using System.Threading;
 using System.Threading.Tasks;

src/MsgPack/Serialization/CodeDomSerializers/CodeDomSerializerBuilder.cs

@@ -1605,7 +1605,7 @@ private void Finish( CodeDomContext context, SerializationTarget targetInfo, boo
 								ctor.Statements.AddRange(
 									this.EmitMemberListInitialization( context, targetInfo ).AsStatements().ToArray()
 								);
-}
+							}
 						}
 					} // if( targetInfo != null )
 

src/MsgPack/Serialization/ReflectionSerializers/ReflectionSerializerHelper.cs

@@ -57,7 +57,7 @@ public static MessagePackSerializer<T> CreateReflectionEnumMessagePackSerializer
 			return
 				ReflectionExtensions.CreateInstancePreservingExceptionType<MessagePackSerializer<T>>(
 					typeof( ReflectionEnumMessagePackSerializer<> ).MakeGenericType( typeof( T ) ),
-					context 
+					context
 				);
 #else
 			return MessagePackSerializer.Wrap<T>( context, new ReflectionEnumMessagePackSerializer( context, typeof( T ) ) );
@@ -221,7 +221,7 @@ public static Action<object, object> GetAddItem( Type targetType, CollectionTrai
 			catch ( ArgumentException )
 			{
 #endif // !AOT || AOT_CHECK
-			return ( collection, item ) => collectionTraits.AddMethod.InvokePreservingExceptionType( collection, item );
+				return ( collection, item ) => collectionTraits.AddMethod.InvokePreservingExceptionType( collection, item );
 #if !AOT || AOT_CHECK
 			}
 #endif // !AOT || AOT_CHECK
@@ -235,10 +235,65 @@ public static void GetMetadata(
 			out Action<object, object>[] setters,
 			out MemberInfo[] memberInfos,
 			out DataMemberContract[] contracts,
-			out MessagePackSerializer[] serializers )
+			out MessagePackSerializer[] serializers
+		)
 		{
 			SerializationTarget.VerifyCanSerializeTargetType( context, targetType );
 
+			if ( members.Count == 0 )
+			{
+				if ( !typeof( IPackable ).IsAssignableFrom( targetType ) )
+				{
+					throw new SerializationException(
+						String.Format(
+							CultureInfo.CurrentCulture,
+							"At least one serializable member is required because type '{0}' does not implement IPackable interface.",
+							targetType
+						)
+					);
+				}
+
+				if ( !typeof( IUnpackable ).IsAssignableFrom( targetType ) )
+				{
+					throw new SerializationException(
+						String.Format(
+							CultureInfo.CurrentCulture,
+							"At least one serializable member is required because type '{0}' does not implement IUnpackable interface.",
+							targetType
+						)
+					);
+				}
+
+#if FEATURE_TAP
+				if ( context.SerializerOptions.WithAsync )
+				{
+					if ( !typeof( IAsyncPackable ).IsAssignableFrom( targetType ) )
+					{
+						throw new SerializationException(
+							String.Format(
+								CultureInfo.CurrentCulture,
+								"At least one serializable member is required because type '{0}' does not implement IAsyncPackable interface.",
+								targetType
+							)
+						);
+					}
+
+					if ( !typeof( IAsyncUnpackable ).IsAssignableFrom( targetType ) )
+					{
+						throw new SerializationException(
+							String.Format(
+								CultureInfo.CurrentCulture,
+								"At least one serializable member is required because type '{0}' does not implement IAsyncUnpackable interface.",
+								targetType
+							)
+						);
+					}
+				}
+
+#endif // FEATURE_TAP
+
+			}
+
 			getters = new Func<object, object>[ members.Count ];
 			setters = new Action<object, object>[ members.Count ];
 			memberInfos = new MemberInfo[ members.Count ];
@@ -364,7 +419,7 @@ public static Func<int, object> CreateCollectionInstanceFactory( Type abstractTy
 			{
 				case 0:
 				{
-					return _ => 
+					return _ =>
 #if !UNITY
 						( T )
 #endif // !UNITY