DeserializeAsync behaviour consistent with its generic counterpart (#3058)

Cache compiled expressions for resolving default(T) from a Type
Remove virtual from methods of InternalSerializer. Users cannot derive from this internal type any more.

Author: russcam

src/Nest/CommonAbstractions/Extensions/TypeExtensions.cs

@@ -15,6 +15,9 @@ internal static class TypeExtensions
 		private static readonly MethodInfo GetActivatorMethodInfo =
 			typeof(TypeExtensions).GetMethod(nameof(GetActivator), BindingFlags.Static | BindingFlags.NonPublic);
 
+		private static readonly ConcurrentDictionary<Type, Func<object>> CachedDefaultValues =
+			new ConcurrentDictionary<Type, Func<object>>();
+
 		private static readonly ConcurrentDictionary<string, ObjectActivator<object>> CachedActivators =
 			new ConcurrentDictionary<string, ObjectActivator<object>>();
 
@@ -29,17 +32,14 @@ internal static class TypeExtensions
 
 		private delegate T ObjectActivator<out T>(params object[] args);
 
-		internal static object CreateGenericInstance(this Type t, Type closeOver, params object[] args)
-		{
-			return t.CreateGenericInstance(new[] {closeOver}, args);
-		}
+		internal static object CreateGenericInstance(this Type t, Type closeOver, params object[] args) =>
+			t.CreateGenericInstance(new[] {closeOver}, args);
 
 		internal static object CreateGenericInstance(this Type t, Type[] closeOver, params object[] args)
 		{
 			var argKey = closeOver.Aggregate(new StringBuilder(), (sb, gt) => sb.Append("--" + gt.FullName), sb => sb.ToString());
 			var key = t.FullName + argKey;
-			Type closedType;
-			if (!CachedGenericClosedTypes.TryGetValue(key, out closedType))
+			if (!CachedGenericClosedTypes.TryGetValue(key, out var closedType))
 			{
 				closedType = t.MakeGenericType(closeOver);
 				CachedGenericClosedTypes.TryAdd(key, closedType);
@@ -71,6 +71,15 @@ internal static object CreateInstance(this Type t, params object[] args)
 			return activator(args);
 		}
 
+		internal static object DefaultValue(this Type type) =>
+			type.IsValueType()
+				? CachedDefaultValues.GetOrAdd(type, t =>
+					Expression.Lambda<Func<object>>(
+						Expression.Convert(Expression.Default(type), typeof(object))
+					).Compile()
+				).Invoke()
+				: null;
+
 		//do not remove this is referenced through GetActivatorMethod
 		private static ObjectActivator<T> GetActivator<T>(ConstructorInfo ctor)
 		{
@@ -88,11 +97,8 @@ private static ObjectActivator<T> GetActivator<T>(ConstructorInfo ctor)
 			{
 				var index = Expression.Constant(i);
 				var paramType = paramsInfo[i].ParameterType;
-
 				var paramAccessorExp = Expression.ArrayIndex(param, index);
-
 				var paramCastExp = Expression.Convert(paramAccessorExp, paramType);
-
 				argsExp[i] = paramCastExp;
 			}
 
@@ -125,8 +131,7 @@ internal static IList<JsonProperty> GetCachedObjectProperties(this Type t,
 
 		internal static IList<PropertyInfo> AllPropertiesCached(this Type t)
 		{
-			IList<PropertyInfo> propertyInfos;
-			if (CachedTypePropertyInfos.TryGetValue(t, out propertyInfos))
+			if (CachedTypePropertyInfos.TryGetValue(t, out var propertyInfos))
 				return propertyInfos;
 			propertyInfos = t.AllPropertiesNotCached().ToList();
 			CachedTypePropertyInfos.TryAdd(t, propertyInfos);

src/Nest/CommonAbstractions/SerializationBehavior/InternalSerializer.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Concurrent;
 using System.IO;
+using System.Linq.Expressions;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -14,6 +16,10 @@ namespace Nest
 	internal class InternalSerializer : IElasticsearchSerializer
 	{
 		private static readonly Encoding ExpectedEncoding = new UTF8Encoding(false);
+
+		//we still support net45 so Task.Completed is not available
+		private static readonly Task CompletedTask = Task.FromResult(false);
+
 		private readonly JsonSerializer _indentedSerializer;
 		internal JsonSerializer Serializer { get; }
 
@@ -66,8 +72,7 @@ public virtual void Serialize<T>(T data, Stream writableStream, SerializationFor
 			}
 		}
 
-		//we still support net45 so Task.Completed is not available
-		private static readonly Task CompletedTask = Task.FromResult(false);
+
 		public Task SerializeAsync<T>(T data, Stream stream, SerializationFormatting formatting = SerializationFormatting.Indented,
 			CancellationToken cancellationToken = default(CancellationToken))
 		{
@@ -77,13 +82,11 @@ public Task SerializeAsync<T>(T data, Stream stream, SerializationFormatting for
 			return CompletedTask;
 		}
 
-		public object Default(Type type) => type.IsValueType() ? type.CreateInstance() : null;
-
-		public virtual T Deserialize<T>(Stream stream) => (T) this.Deserialize(typeof(T), stream);
+		public T Deserialize<T>(Stream stream) => (T) this.Deserialize(typeof(T), stream);
 
-		public virtual object Deserialize(Type type, Stream stream)
+		public object Deserialize(Type type, Stream stream)
 		{
-			if (stream == null) return Default(type);
+			if (stream == null) return type.DefaultValue();
 			using (var streamReader = new StreamReader(stream))
 			using (var jsonTextReader = new JsonTextReader(streamReader))
 			{
@@ -92,8 +95,9 @@ public virtual object Deserialize(Type type, Stream stream)
 			}
 		}
 
-		public virtual async Task<T> DeserializeAsync<T>(Stream stream, CancellationToken cancellationToken = default(CancellationToken))
+		public async Task<T> DeserializeAsync<T>(Stream stream, CancellationToken cancellationToken = default(CancellationToken))
 		{
+			if (stream == null) return default(T);
 			using (var streamReader = new StreamReader(stream))
 			using (var jsonTextReader = new JsonTextReader(streamReader))
 			{
@@ -108,18 +112,26 @@ public virtual object Deserialize(Type type, Stream stream)
 				}
 				catch
 				{
-					return await Task.FromResult(default(T)).ConfigureAwait(false);
+					return default(T);
 				}
 			}
 		}
 
-		public virtual async Task<object> DeserializeAsync(Type type, Stream stream, CancellationToken cancellationToken = default(CancellationToken))
+		public async Task<object> DeserializeAsync(Type type, Stream stream, CancellationToken cancellationToken = default(CancellationToken))
 		{
+			if (stream == null) return type.DefaultValue();
 			using (var streamReader = new StreamReader(stream))
 			using (var jsonTextReader = new JsonTextReader(streamReader))
 			{
-				var token = await JToken.LoadAsync(jsonTextReader, cancellationToken).ConfigureAwait(false);
-				return token.ToObject(type, this.Serializer);
+				try
+				{
+					var token = await JToken.LoadAsync(jsonTextReader, cancellationToken).ConfigureAwait(false);
+					return token.ToObject(type, this.Serializer);
+				}
+				catch
+				{
+					return type.DefaultValue();
+				}
 			}
 		}