added missing null_value and existence properties to missing filter fix #796

Author: Mpdreamz

src/Nest/DSL/Filter/FilterDescriptor.cs

@@ -89,23 +89,28 @@ public FilterContainer Exists(string field)
 		/// <summary>
 		/// Filters documents where a specific field has no value in them.
 		/// </summary>
-		public FilterContainer Missing(Expression<Func<T, object>> fieldDescriptor)
+		public FilterContainer Missing(Expression<Func<T, object>> fieldDescriptor, Action<MissingFilterDescriptor> selector = null)
 		{
-			IMissingFilter filter = new MissingFilterDescriptor();
+			var mf = new MissingFilterDescriptor();
+			if (selector != null) selector(mf);
+			IMissingFilter filter = mf;
 			filter.Field = fieldDescriptor;
 			this.SetCacheAndName(filter);
 			return  this.New(filter, f => f.Missing = filter);
 		}
 		/// <summary>
 		/// Filters documents where a specific field has no value in them.
 		/// </summary>
-		public FilterContainer Missing(string field)
+		public FilterContainer Missing(string field, Action<MissingFilterDescriptor> selector = null)
 		{
-			IMissingFilter filter = new MissingFilterDescriptor();
+			var mf = new MissingFilterDescriptor();
+			if (selector != null) selector(mf);
+			IMissingFilter filter = mf;
 			filter.Field = field;
 			this.SetCacheAndName(filter);
 			return  this.New(filter, f => f.Missing = filter);
 		}
+
 		/// <summary>
 		/// Filters documents that only have the provided ids. 
 		/// Note, this filter does not require the _id field to be indexed since it works using the _uid field.

src/Nest/DSL/Filter/MissingFilterDescriptor.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Linq.Expressions;
 using Nest.Resolvers.Converters;
 using Newtonsoft.Json;
 
@@ -12,6 +13,12 @@ public interface IMissingFilter : IFilter
 	{
 		[JsonProperty(PropertyName = "field")]
 		PropertyPathMarker Field { get; set; }
+
+		[JsonProperty(PropertyName = "existence")]
+		bool? Existence { get; set; }
+
+		[JsonProperty(PropertyName = "null_value")]
+		bool? NullValue { get; set; }
 	}
 
 	public class MissingFilter : PlainFilter, IMissingFilter
@@ -22,6 +29,10 @@ protected internal override void WrapInContainer(IFilterContainer container)
 		}
 
 		public PropertyPathMarker Field { get; set; }
+
+		public bool? Existence { get; set; }
+
+		public bool? NullValue { get; set; }
 	}
 
 	public class MissingFilterDescriptor : FilterBase, IMissingFilter
@@ -35,6 +46,22 @@ bool IFilter.IsConditionless
 
 		}
 
+		private IMissingFilter Self { get { return this; } }
+
 		PropertyPathMarker IMissingFilter.Field { get; set;}
+		bool? IMissingFilter.Existence { get; set; }
+		bool? IMissingFilter.NullValue { get; set; }
+
+		public MissingFilterDescriptor Existence(bool existence = true)
+		{
+			Self.Existence = existence;
+			return this;
+		}
+
+		public MissingFilterDescriptor NullValue(bool nullValue = true)
+		{
+			Self.NullValue = nullValue;
+			return this;
+		}
 	}
 }

src/Tests/Nest.Tests.Unit/QueryParsers/Filter/MissingFilterTests.cs

@@ -12,10 +12,12 @@ public void Missing_Deserializes(string cacheName, string cacheKey, bool cache)
 		{
 			var missingFilter = this.SerializeThenDeserialize(cacheName, cacheKey, cache, 
 				f=>f.Missing,
-				f=>f.Missing(p=>p.Name)
+				f=>f.Missing(p=>p.Name, m=>m.Existence(false).NullValue(true))
 				);
 
 			missingFilter.Field.Should().Be("name");
+			missingFilter.Existence.Should().Be(false);
+			missingFilter.NullValue.Should().Be(true);
 		}
 
 	}