Append #2231 Made field_masking_span a top level query

As per elastic/elasticsearch#3007 this is now possible (before 1.x GA)

Added additional serialization tests

src/Nest/DSL/Query/QueryDescriptor.cs

@@ -886,6 +886,27 @@ public QueryContainer SpanMultiTerm(Action<SpanMultiTermQueryDescriptor<T>> sele
 			return this.New(span, q => q.SpanMultiTerm = span);
 		}
 
+		/// <summary>
+		/// Wrapper to allow span queries participate in composite single-field span queries by 
+		/// 'lying' about their search field. The span field masking query maps to Lucene `SpanFieldMaskingQuery`
+		/// 
+		/// This can be used to support queries like `span-near` or `span-or` across different fields, which is not ordinarily permitted.
+		/// Span field masking query is invaluable in conjunction with *multi-fields* when same content is 
+		/// indexed with multiple analyzers. For instance we could index a field with the standard analyzer 
+		/// which breaks text up into words, and again with the english analyzer which stems words into their root 
+		/// form. That will add more precision to queries. Wrap a multi term query (one of fuzzy, prefix, term range or regexp query) 
+		/// as a span query so it can be nested.
+		/// </summary>
+		public QueryContainer SpanFieldMasking(Action<SpanFieldMaskingQueryDescriptor<T>> selector)
+		{
+			selector.ThrowIfNull("selector");
+			var span = new SpanFieldMaskingQueryDescriptor<T>();
+			selector(span);
+
+			return this.New(span, q => q.SpanFieldMasking= span);
+		}
+
+
 		/// <summary>
 		/// custom_score query allows to wrap another query and customize the scoring of it optionally with a 
 		/// computation derived from other field values in the doc (numeric ones) using script or boost expression

src/Nest/DSL/Query/SpanFieldMaskingQueryDescriptor.cs

@@ -10,47 +10,47 @@ namespace Nest
 	[JsonObject(MemberSerialization = MemberSerialization.OptIn)]
 	[JsonConverter(typeof(ReadAsTypeConverter<SpanFieldMaskingQueryDescriptor<object>>))]
 	public interface ISpanFieldMaskingQuery : ISpanSubQuery, IFieldNameQuery
-    {
-        [JsonProperty(PropertyName = "field")]
-        PropertyPathMarker Field { get; set; }
-        
-        [JsonProperty(PropertyName = "query")]
+	{
+		[JsonProperty(PropertyName = "field")]
+		PropertyPathMarker Field { get; set; }
+
+		[JsonProperty(PropertyName = "query")]
 		ISpanQuery Query { get; set; }
 	}
 
 	public class SpanFieldMaskingQuery : PlainQuery, ISpanFieldMaskingQuery
-    {
+	{
 		protected override void WrapInContainer(IQueryContainer container)
 		{
 			container.SpanFieldMasking = this;
 		}
 
 		bool IQuery.IsConditionless { get { return false; } }
 
-        public string Name { get; set; }
-        public PropertyPathMarker Field { get; set; }
-        public ISpanQuery Query { get; set; }
+		public string Name { get; set; }
+		public PropertyPathMarker Field { get; set; }
+		public ISpanQuery Query { get; set; }
 
-        PropertyPathMarker IFieldNameQuery.GetFieldName()
-        {
-            return this.Field;
-        }
+		PropertyPathMarker IFieldNameQuery.GetFieldName()
+		{
+			return this.Field;
+		}
 
-        void IFieldNameQuery.SetFieldName(string fieldName)
-        {
-            this.Field = fieldName;
-        }
-    }
+		void IFieldNameQuery.SetFieldName(string fieldName)
+		{
+			this.Field = fieldName;
+		}
+	}
 
 	public class SpanFieldMaskingQueryDescriptor<T> : ISpanFieldMaskingQuery where T : class
 	{
 		ISpanFieldMaskingQuery Self { get { return this; } }
-        bool IQuery.IsConditionless { get { return false; } }
+		bool IQuery.IsConditionless { get { return false; } }
 
-        ISpanQuery ISpanFieldMaskingQuery.Query { get; set; }
-        PropertyPathMarker ISpanFieldMaskingQuery.Field { get; set; }
-        string IQuery.Name { get; set; }
-        
+		ISpanQuery ISpanFieldMaskingQuery.Query { get; set; }
+		PropertyPathMarker ISpanFieldMaskingQuery.Field { get; set; }
+		string IQuery.Name { get; set; }
+		
 		public SpanFieldMaskingQueryDescriptor<T> Name(string name)
 		{
 			Self.Name = name;
@@ -71,26 +71,26 @@ public SpanFieldMaskingQueryDescriptor<T> OnField(string field)
 			return this;
 		}
 
-        public SpanFieldMaskingQueryDescriptor<T> OnField(Expression<Func<T, object>> field)
-        {
-            Self.Field = field;
-            return this;
-        }
+		public SpanFieldMaskingQueryDescriptor<T> OnField(Expression<Func<T, object>> field)
+		{
+			Self.Field = field;
+			return this;
+		}
 
-        public SpanFieldMaskingQueryDescriptor<T> OnField<K>(Expression<Func<T, K>> field)
-        {
-            Self.Field = field;
-            return this;
-        }
-        
-        public PropertyPathMarker GetFieldName()
-        {
-            return Self.Field;
-        }
+		public SpanFieldMaskingQueryDescriptor<T> OnField<K>(Expression<Func<T, K>> field)
+		{
+			Self.Field = field;
+			return this;
+		}
+		
+		public PropertyPathMarker GetFieldName()
+		{
+			return Self.Field;
+		}
 
-        public void SetFieldName(string fieldName)
-        {
-            Self.Field = fieldName;
-        }
-    }
+		public void SetFieldName(string fieldName)
+		{
+			Self.Field = fieldName;
+		}
+	}
 }

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

@@ -406,6 +406,7 @@
     <Compile Include="QueryParsers\Queries\SpanOrQueryTests.cs" />
     <Compile Include="QueryParsers\Queries\SpanTermQueryTests.cs" />
     <Compile Include="QueryParsers\Queries\TermQueryTests.cs" />
+    <Compile Include="QueryParsers\Queries\FieldMaskingSpanQueryTests.cs" />
     <Compile Include="QueryParsers\Queries\TermsQueryTests.cs" />
     <Compile Include="QueryParsers\Queries\WildCardQueryTests.cs" />
     <Compile Include="QueryParsers\Visitor\DslPrettyPrintVisitor.cs" />

src/Tests/Nest.Tests.Unit/QueryParsers/Queries/FieldMaskingSpanQueryTests.cs

@@ -0,0 +1,24 @@
+using FluentAssertions;
+using Nest.Tests.MockData.Domain;
+using NUnit.Framework;
+
+namespace Nest.Tests.Unit.QueryParsers.Queries
+{
+	[TestFixture]
+	public class FieldMaskingSpanQueryTests : ParseQueryTestsBase
+	{
+		[Test]
+		public void FieldMaskingSpan_Deserializes()
+		{
+			var q = this.SerializeThenDeserialize(
+				f => f.SpanFieldMasking,
+				f => f.SpanFieldMasking(s => s.OnField(p => p.Name).Query(qq => qq.SpanTerm("x", "y")))
+			);
+
+
+			q.Field.Should().NotBeNull().And.Be("name");
+			q.Query.Should().NotBeNull();
+			q.Query.SpanTermQueryDescriptor.Should().NotBeNull();
+		}
+	}
+}