Support multiple forms of source filter when deserializing

Closes #1796

Author: russcam

src/Benchmarking/project.lock.json

@@ -2025,7 +2025,7 @@
     "System.Dynamic.Runtime/4.0.11-beta-23516": {
       "type": "package",
       "serviceable": true,
-      "sha512": "C2GXB20I5vMcO4wemZr5pEjwwEb6H6zVkwF12JSUhripKBIKgI0YKpfp9glyDSL903cYgIXAztMQDajwCR0PmA==",
+      "sha512": "ypkxS0e+yUw7F6JEwuB22u0qqruMeZFOmtcImh2efDHpTAuhF2FOqCDJ7f4qLf9yomVvB4kjkZ6xGunbIQryxQ==",
       "files": [
         "lib/DNXCore50/System.Dynamic.Runtime.dll",
         "lib/MonoAndroid10/_._",

src/Elasticsearch.Net/project.lock.json

@@ -3,7 +3,7 @@
 
 namespace Nest
 {
-	[JsonConverter(typeof(ReadAsTypeJsonConverter<SourceFilter>))]
+	[JsonConverter(typeof(SourceFilterJsonConverter))]
 	public interface ISourceFilter
 	{
 		[JsonProperty("include")]

src/Nest/Search/Search/SourceFiltering/SourceFilter.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Collections.Generic;
+using Newtonsoft.Json;
+
+namespace Nest
+{
+	public class SourceFilterJsonConverter : JsonConverter
+	{
+		public override bool CanRead => true;
+		public override bool CanWrite => false;
+		public override bool CanConvert(Type objectType) => true;
+
+		public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+		{
+		}
+
+		public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+		{
+			if (reader.TokenType == JsonToken.Null) return null;
+
+			var filter =  new SourceFilter();
+			switch (reader.TokenType)
+			{
+				case JsonToken.Boolean:
+					filter.Exclude = new[] { "*" };
+					break;
+				case JsonToken.String:
+					filter.Include = new [] { (string)reader.Value };
+					break;
+				case JsonToken.StartArray:
+					var include = new List<string>();
+					while (reader.Read() && reader.TokenType != JsonToken.EndArray)
+						include.Add((string)reader.Value);
+					filter.Include = include.ToArray();
+					break;
+				default:
+					serializer.Populate(reader, filter);
+					break;
+			}
+
+			return filter;
+		}
+	}
+}

src/Nest/Search/Search/SourceFiltering/SourceFilterJsonConverter.cs

@@ -2037,7 +2037,7 @@
     "runtime.any.System.Linq.Expressions/4.0.11-beta-23516": {
       "type": "package",
       "serviceable": true,
-      "sha512": "P5nzo1Ye0GxB4BYdWian6Y427eTrhn1JS3jLWZq5bMWVn8hS/OIfyylASN0A/qqeLn4rGA0fOzmJSYqFSKvxgQ==",
+      "sha512": "4sPxQCjllMJ1uZNlwz/EataPyHSH+AqSDlOIPPqcy/88R2B+abfhPPC78rd7gvHp8KmMX4qbJF6lcCeDIQpmVg==",
       "files": [
         "lib/DNXCore50/System.Linq.Expressions.dll",
         "lib/MonoAndroid10/_._",
@@ -2345,7 +2345,7 @@
     "System.Dynamic.Runtime/4.0.11-beta-23516": {
       "type": "package",
       "serviceable": true,
-      "sha512": "C2GXB20I5vMcO4wemZr5pEjwwEb6H6zVkwF12JSUhripKBIKgI0YKpfp9glyDSL903cYgIXAztMQDajwCR0PmA==",
+      "sha512": "ypkxS0e+yUw7F6JEwuB22u0qqruMeZFOmtcImh2efDHpTAuhF2FOqCDJ7f4qLf9yomVvB4kjkZ6xGunbIQryxQ==",
       "files": [
         "lib/DNXCore50/System.Dynamic.Runtime.dll",
         "lib/MonoAndroid10/_._",
@@ -2599,7 +2599,7 @@
     "System.Linq.Expressions/4.0.11-beta-23516": {
       "type": "package",
       "serviceable": true,
-      "sha512": "FtKytB13HabzrSvrAgBgOOnG2uxJO4s7zvP5Sk0NS3bwbJUyb5AP1p4897UWnLiB6C95jI4nIkZps51sa9In8g==",
+      "sha512": "YEl5oyF5fifLbHHP099cvb/6f2r2h1QVHzoaoINPHOZtpNec+RfqvzETXcYDIdHT7l+bBAYsBuVUkBgfQEoYfQ==",
       "files": [
         "lib/MonoAndroid10/_._",
         "lib/MonoTouch10/_._",

src/Nest/project.lock.json

@@ -104,7 +104,7 @@ private void Sort(JObject jObj)
 			}
 		}
 
-		private TObject Deserialize<TObject>(string json) =>
+		protected TObject Deserialize<TObject>(string json) =>
 			GetSerializer().Deserialize<TObject>(new MemoryStream(Encoding.UTF8.GetBytes(json)));
 
 		protected string Serialize<TObject>(TObject o)

src/Tests/Framework/SerializationTestBase.cs

@@ -0,0 +1,106 @@
+using System;
+using Tests.Framework.Integration;
+using Tests.Framework.MockData;
+using Nest;
+using FluentAssertions;
+using Tests.Framework;
+using Newtonsoft.Json;
+using static Nest.Infer;
+
+namespace Tests.Search.Request
+{
+	/** Allows to control how the _source field is returned  with every hit.
+	 *	By default operations return the contents of the _source field unless 
+	 *  you have used the fields parameter or if the _source field is disabled.
+	 */
+	public class SourceFilteringUsageTests : SearchUsageTestBase
+	{
+		public SourceFilteringUsageTests(ReadOnlyCluster cluster, EndpointUsage usage) : base(cluster, usage) { }
+
+		protected override object ExpectJson =>
+			new
+			{
+				_source = new
+				{
+					include = new[] { "name", "startedOn" }
+				}
+			};
+
+		protected override Func<SearchDescriptor<Project>, ISearchRequest> Fluent => s => s
+			.Source(so => so
+				.Include(f => f
+					.Fields(
+						p => p.Name,
+						p => p.StartedOn
+					)
+				)
+			);
+
+		protected override SearchRequest<Project> Initializer =>
+			new SearchRequest<Project>
+			{
+				Source = new SourceFilter
+				{
+					Include = Fields<Project>(p => p.Name, prop => prop.StartedOn)
+				}
+			};
+
+		protected override void ExpectResponse(ISearchResponse<Project> response)
+		{
+			response.IsValid.Should().BeTrue();
+
+			foreach (var document in response.Documents)
+			{
+				document.Name.Should().NotBeNull();
+				document.StartedOn.Should().NotBe(default(DateTime));
+				document.Description.Should().BeNull();
+			}
+		}
+	}
+
+	public class SourceFilteringSerializationTests : SerializationTestBase
+	{
+		internal class WithSourceFilterProperty
+		{
+			[JsonProperty("_source")]
+			public ISourceFilter SourceFilter { get; set; }
+		}
+
+		[U]
+		public void CanDeserializeBoolean()
+		{
+			var o = base.Deserialize<WithSourceFilterProperty>("{ \"_source\": false }");
+			o.Should().NotBeNull();
+			o.SourceFilter.Should().NotBeNull();
+			o.SourceFilter.Exclude.Should().Contain("*");
+		}
+
+		[U]
+		public void CanDeserializeArray()
+		{
+			var o = base.Deserialize<WithSourceFilterProperty>("{ \"_source\": [\"obj.*\"] }");
+			o.Should().NotBeNull();
+			o.SourceFilter.Should().NotBeNull();
+			o.SourceFilter.Include.Should().Contain("obj.*");
+		}
+
+		[U]
+		public void CanDeserializeString()
+		{
+			var o = base.Deserialize<WithSourceFilterProperty>("{ \"_source\": \"obj.*\" }");
+			o.Should().NotBeNull();
+			o.SourceFilter.Should().NotBeNull();
+			o.SourceFilter.Include.Should().Contain("obj.*");
+		}
+
+		[U]
+		public void CanDeserializeObject()
+		{
+			var o = base.Deserialize<WithSourceFilterProperty>("{ \"_source\": { \"include\": [\"obj.*\"], \"exclude\": [\"foo.*\"] } }");
+			o.Should().NotBeNull();
+			o.SourceFilter.Should().NotBeNull();
+			o.SourceFilter.Include.Should().Contain("obj.*");
+			o.SourceFilter.Exclude.Should().Contain("foo.*");
+		}
+	}
+}