Added filter support for HasChild filter.

src/Nest/DSL/Filter/HasChildFilterDescriptor.cs

@@ -15,6 +15,9 @@ public interface IHasChildFilter : IFilter
 
 		[JsonProperty("query")]
 		IQueryContainer Query { get; set; }
+
+		[JsonProperty("filter")]
+		IFilterContainer Filter { get; set; }
 	}
 
 	public class HasChildFilter : PlainFilter, IHasChildFilter
@@ -26,6 +29,7 @@ protected internal override void WrapInContainer(IFilterContainer container)
 
 		public TypeNameMarker Type { get; set; }
 		public IQueryContainer Query { get; set; }
+		public IFilterContainer Filter { get; set; }
 	}
 
 	public class HasChildFilterDescriptor<T> : FilterBase, IHasChildFilter where T : class
@@ -35,15 +39,25 @@ bool IFilter.IsConditionless
 			get
 			{
 				var hf = ((IHasChildFilter)this);
-				return hf.Query == null || hf.Query.IsConditionless || hf.Type.IsNullOrEmpty();
+				if (hf.Type.IsNullOrEmpty())
+					return true;
+
+				if (hf.Query == null && hf.Filter == null)
+					return true;
+				if (hf.Filter == null && hf.Query != null)
+					return hf.Query.IsConditionless;
+				if (hf.Filter != null && hf.Query == null)
+					return hf.Filter.IsConditionless;
+				return hf.Query.IsConditionless && hf.Filter.IsConditionless;
 			}
 		}
 
 		TypeNameMarker IHasChildFilter.Type { get; set; }
 
-
 		IQueryContainer IHasChildFilter.Query { get; set; }
 
+		IFilterContainer IHasChildFilter.Filter { get; set; }
+
 		public HasChildFilterDescriptor()
 		{
 			((IHasChildFilter)this).Type = TypeNameMarker.Create<T>();
@@ -55,7 +69,14 @@ public HasChildFilterDescriptor<T> Query(Func<QueryDescriptor<T>, QueryContainer
 			((IHasChildFilter)this).Query = querySelector(q);
 			return this;
 		}
-
+
+		public HasChildFilterDescriptor<T> Filter(Func<FilterDescriptor<T>, FilterContainer> filterSelector)
+		{
+			var f = new FilterDescriptor<T>();
+			((IHasChildFilter) this).Filter = filterSelector(f);
+			return this;
+		}
+
 		public HasChildFilterDescriptor<T> Type(string type)
 		{
 			((IHasChildFilter)this).Type = type;

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

@@ -14,13 +14,18 @@ public void HasChild_Deserializes(string cacheName, string cacheKey, bool cache)
 			var hasChildFilter = this.SerializeThenDeserialize(cacheName, cacheKey, cache, 
 				f=>f.HasChild,
 				f=>f.HasChild<Person>(d=>d
-					.Query(q=>q.Term(p=>p.FirstName, "value"))
+					.Query(q => q.Term(p => p.FirstName, "value"))
+					.Filter(q => q.Term(p => p.Age, 42))
 					)
 				);
 
 			var query = hasChildFilter.Query;
 			query.Should().NotBeNull();
 			query.Term.Field.Should().Be("firstName");
+
+			var filter = hasChildFilter.Filter;
+			filter.Should().NotBeNull();
+			filter.Term.Field.Should().Be("age");
 		}
 
 	}

src/Tests/Nest.Tests.Unit/Search/Filter/ConditionLess/ConditionLessTests.cs

@@ -116,6 +116,8 @@ public void HasChildTest()
 		{
 			this.DoConditionlessFilter(f => f.HasChild<Person>(null));
 			this.DoConditionlessFilter(f => f.HasChild<Person>(q=>q.Query(qq=>qq.Term(p=>p.FirstName, string.Empty))));
+			this.DoConditionlessFilter(f => f.HasChild<Person>(q=>q.Filter(qq=>qq.Term(p=>p.FirstName, string.Empty))));
+			this.DoConditionlessFilter(f => f.HasChild<Person>(q => q.Query(qq => qq.Term(p => p.FirstName, string.Empty)).Filter(qq => qq.Term(p => p.FirstName, string.Empty))));
 		}
 
 

src/Tests/Nest.Tests.Unit/Search/Filter/Singles/HasChildFilterJson.cs

@@ -12,7 +12,8 @@ public void HasChildFilter()
 			var s = new SearchDescriptor<ElasticsearchProject>().From(0).Size(10)
 				.Filter(ff=>ff
 					.HasChild<Person>(d=>d
-						.Query(q=>q.Term(p=>p.FirstName, "value"))
+						.Query(q => q.Term(p => p.FirstName, "value"))
+						.Filter(q => q.Term(p => p.Age, 42))
 					)
 				);
 
@@ -27,6 +28,11 @@ public void HasChildFilter()
 							""value"": ""value""
 						  }
 						}
+					  },
+					  ""filter"": {
+						""term"": {
+						  ""age"": 42
+						}
 					  }
 					}
 				}