fix #1352 add support for _field_names mapping

src/Nest/DSL/PutMappingDescriptor.cs

@@ -265,12 +265,20 @@ public PutMappingDescriptor<T> RoutingField(Func<RoutingFieldMappingDescriptor<T
 			Self.Mapping.RoutingFieldMapping = routingMapper(new RoutingFieldMappingDescriptor<T>());
 			return this;
 		}
+
 		public PutMappingDescriptor<T> TimestampField(Func<TimestampFieldMappingDescriptor<T>, ITimestampFieldMapping> timestampMapper)
 		{
 			timestampMapper.ThrowIfNull("timestampMapper");
 			Self.Mapping.TimestampFieldMapping = timestampMapper(new TimestampFieldMappingDescriptor<T>());
 			return this;
 		}
+
+		public PutMappingDescriptor<T> FieldNamesField(Func<FieldNamesFieldMappingDescriptor<T>, IFieldNamesFieldMapping> fieldNamesMapper)
+		{
+			Self.Mapping.FieldNamesFieldMapping = fieldNamesMapper == null ? null : fieldNamesMapper(new FieldNamesFieldMappingDescriptor<T>());
+			return this;
+		}
+
 		public PutMappingDescriptor<T> TtlField(Func<TtlFieldMappingDescriptor, ITtlFieldMapping> ttlFieldMapper)
 		{
 			ttlFieldMapper.ThrowIfNull("ttlFieldMapper");

src/Nest/Domain/Mapping/SpecialFields/FieldNamesMapping.cs

@@ -0,0 +1,34 @@
+using System;
+using Newtonsoft.Json;
+using System.Linq.Expressions;
+using Nest.Resolvers.Converters;
+
+namespace Nest
+{
+	[JsonConverter(typeof(ReadAsTypeConverter<FieldNamesFieldMapping>))]
+	public interface IFieldNamesFieldMapping : ISpecialField
+	{
+		[JsonProperty("enabled")]
+		bool Enabled { get; set; }
+	}
+
+	public class FieldNamesFieldMapping : IFieldNamesFieldMapping
+	{
+		public bool Enabled { get; set; }
+	}
+
+
+	public class FieldNamesFieldMappingDescriptor<T> : IFieldNamesFieldMapping
+	{
+		private IFieldNamesFieldMapping Self { get { return this; } }
+
+		bool IFieldNamesFieldMapping.Enabled { get; set;}
+
+		public FieldNamesFieldMappingDescriptor<T> Enabled(bool enabled = true)
+		{
+			Self.Enabled = enabled;
+			return this;
+		}
+
+	}
+}

src/Nest/Domain/Mapping/Types/RootObjectMapping.cs

@@ -65,6 +65,9 @@ public class RootObjectMapping : ObjectMapping
 		[JsonProperty("_timestamp")]
 		public ITimestampFieldMapping TimestampFieldMapping { get; set; }
 
+		[JsonProperty("_field_names")]
+		public IFieldNamesFieldMapping FieldNamesFieldMapping { get; set; }
+
 		[JsonProperty("_ttl")]
 		public ITtlFieldMapping TtlFieldMappingDescriptor { get; set; }
 

src/Nest/Nest.csproj

@@ -153,6 +153,7 @@
     <Compile Include="Domain\Geo\MultiPolygonGeoShape.cs" />
     <Compile Include="Domain\Geo\PointGeoShape.cs" />
     <Compile Include="Domain\Geo\PolygonGeoShape.cs" />
+    <Compile Include="Domain\Mapping\SpecialFields\FieldNamesMapping.cs" />
     <Compile Include="Domain\Mapping\SubMappings\FieldData\FieldDataFilter.cs" />
     <Compile Include="Domain\Mapping\SubMappings\FieldData\FieldDataFrequencyFilter.cs" />
     <Compile Include="Domain\Mapping\SubMappings\FieldData\FieldDataMapping.cs" />

src/Tests/Nest.Tests.Unit/Core/Map/FieldNamesField/FieldNamesFieldTests.cs

@@ -0,0 +1,19 @@
+using NUnit.Framework;
+using Nest.Tests.MockData.Domain;
+using System.Reflection;
+
+namespace Nest.Tests.Unit.Core.Map.FieldNamesField
+{
+	[TestFixture]
+	public class FieldNamesFieldTests : BaseJsonTests
+	{
+		[Test]
+		public void FieldNamesMapping()
+		{
+			var result = this._client.Map<ElasticsearchProject>(m => m
+				.FieldNamesField(a => a .Enabled(false))
+			);
+			this.JsonEquals(result.ConnectionStatus.Request, MethodBase.GetCurrentMethod()); 
+		}
+	}
+}

src/Tests/Nest.Tests.Unit/Core/Map/FieldNamesField/FieldNamesMapping.json

@@ -0,0 +1,7 @@
+  {
+  "elasticsearchprojects": {
+    "_field_names": {
+      "enabled": false
+    }
+  }
+}

src/Tests/Nest.Tests.Unit/Nest.Tests.Unit.csproj

@@ -199,6 +199,7 @@
     <None Include="Core\Map\Properties\MultiFieldPropertyWithJustNamePath.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <Compile Include="Core\Map\FieldNamesField\FieldNamesFieldTests.cs" />
     <Compile Include="Core\MultiPercolate\MultiPercolateTests.cs" />
     <Compile Include="Core\Map\Transform\MappingTansformTests.cs" />
     <Compile Include="Core\Repository\RestoreTests.cs" />
@@ -637,6 +638,9 @@
     <None Include="Core\Map\MetaField\MetaFieldSerializes.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Include="Core\Map\FieldNamesField\FieldNamesMapping.json">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
     <None Include="Core\Map\Transform\MultipleTransforms.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>