Use serializer when deserializing LazyDocument to T

When converting a LazyDocument to type T, use the JsonNetSerializer configured, along with all registered contract resolvers.

Fixes #2788

Author: russcam

src/Nest/CommonAbstractions/LazyDocument/LazyDocument.cs

@@ -17,11 +17,12 @@ public interface ILazyDocument
 	public class LazyDocument : ILazyDocument
 	{
 		internal JToken _Value { get; set; }
+		internal JsonSerializer _Serializer { get; set; }
 
 		public T As<T>() where T : class
 		{
 			var jToken = this._Value;
-			return jToken?.ToObject<T>();
+			return jToken?.ToObject<T>(_Serializer);
 		}
 	}
 }

src/Nest/CommonAbstractions/LazyDocument/LazyDocumentJsonConverter.cs

@@ -10,19 +10,24 @@ public override void WriteJson(JsonWriter writer, object value, JsonSerializer s
 		{
 			var d = value as LazyDocument;
 			if (d?._Value == null)
+			{
+				writer.WriteNull();
 				return;
+			}
+
 			writer.WriteToken(d._Value.CreateReader());
 		}
 
 		public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
 		{
 			var document = serializer.Deserialize(reader) as JToken;
-			return new LazyDocument { _Value = document };
+			return new LazyDocument
+			{
+				_Value = document,
+				_Serializer = serializer
+			};
 		}
 
-		public override bool CanConvert(Type objectType)
-		{
-			return true;
-		}
+		public override bool CanConvert(Type objectType) => true;
 	}
 }

src/Nest/Search/Search/Hits/InnerHitsResult.cs

@@ -6,13 +6,15 @@ namespace Nest
 {
 	public class InnerHitsResult
 	{
-		
 		[JsonProperty("hits")]
 		public InnerHitsMetaData Hits { get; internal set; }
 
-		public IEnumerable<T> Documents<T>() where T : class
-		{
-			return this.Hits == null ? Enumerable.Empty<T>() : this.Hits.Documents<T>();
-		}
+		/// <summary>
+		/// Retrieve <see cref="Hits"/> documents as a strongly typed
+		/// collection
+		/// </summary>
+		/// <typeparam name="T">The hits document type</typeparam>
+		public IEnumerable<T> Documents<T>() where T : class => 
+			this.Hits == null ? Enumerable.Empty<T>() : this.Hits.Documents<T>();
 	}
 }

src/Tests/Reproduce/GithubIssue2788.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Linq;
+using Elasticsearch.Net;
+using FluentAssertions;
+using FluentAssertions.Common;
+using Nest;
+using Tests.Framework;
+using Tests.Framework.ManagedElasticsearch.Clusters;
+using Xunit;
+
+namespace Tests.Reproduce
+{
+	public class GithubIssue2788 : IClusterFixture<WritableCluster>
+	{
+		private readonly WritableCluster _cluster;
+
+		public GithubIssue2788(WritableCluster cluster)
+		{
+			_cluster = cluster;
+		}
+
+		// sample mapping with nested objects with TimeSpan field
+		class Root
+		{
+			[Nested]
+			public Child[] Children { get; set; }
+		}
+
+		class Child
+		{
+			public TimeSpan StartTime { get; set; }
+
+			public TimeSpan EndTime { get; set; }
+		}
+
+		[I]
+		public void CanDeserializeNumberToTimeSpanInInnerHits()
+		{
+			var indexName = "sample";
+			var client = _cluster.Client;
+
+			//create index with automapping
+			client.CreateIndex(indexName, create => create
+				.Mappings(mappings => mappings
+					.Map<Root>(map => map
+						.AutoMap()
+					)
+				)
+			);
+
+			var startTime = new TimeSpan(1, 2, 3);
+			var endTime = new TimeSpan(2, 3, 4);
+
+			client.Index(new Root
+			{
+				Children = new[]
+				{
+					new Child
+					{
+						StartTime = startTime,
+						EndTime = endTime
+
+					}
+				}
+			}, index => index
+				.Index(indexName)
+				.Refresh(Refresh.WaitFor)
+			);
+
+			var result = client.Search<Root>(search => search
+				.Query(query => query
+					.Nested(nested => nested
+						.Query(nestedQuery => nestedQuery
+							.MatchAll()
+						)
+						.Path(i => i.Children)
+						.InnerHits()
+					)
+				)
+				.Index(indexName)
+			);
+
+			var child = result.Hits.First().InnerHits.Single().Value.Documents<Child>().Single();
+
+			child.Should().NotBeNull();
+			child.StartTime.Should().Be(startTime);
+			child.EndTime.Should().Be(endTime);
+		}
+	}
+}