Correctly deserialize JoinField (#3357)

* Correctly deserialize JoinField

When the join field is a string and using JsonNetSerializer, the string
conversion should not emit the surrounding double quotes

Closes #3356

* Use SerializationTester

Update following PR

Author: russcam

src/Serializers/Nest.JsonNetSerializer/Converters/HandleNestTypesOnSourceJsonConverter.cs

@@ -45,7 +45,7 @@ public override object ReadJson(JsonReader reader, Type objectType, object exist
 			//even though we pass type JSON.NET won't try the registered converter for that type
 			//even if it can handle string tokens :(
 			if (objectType == typeof(JoinField) && token.Type == JTokenType.String)
-				return JoinField.Root(token.ToString(Formatting.None));
+				return JoinField.Root(token.Value<string>());
 
 			using (var ms = token.ToStream())
 				return _builtInSerializer.Deserialize(objectType, ms);

src/Tests/Tests.Core/Client/TestClient.cs

@@ -1,4 +1,5 @@
 using Nest;
+using Nest.JsonNetSerializer;
 using Tests.Configuration;
 using Tests.Core.Client.Settings;
 using Tests.Domain.Extensions;
@@ -9,6 +10,8 @@ public static class TestClient
 	{
 		public static readonly IElasticClient Default = new ElasticClient(new TestConnectionSettings().ApplyDomainSettings());
 		public static readonly IElasticClient DefaultInMemoryClient = new ElasticClient(new AlwaysInMemoryConnectionSettings().ApplyDomainSettings());
+		public static readonly IElasticClient InMemoryWithJsonNetSerializer = new ElasticClient(
+			new AlwaysInMemoryConnectionSettings(sourceSerializerFactory: JsonNetSerializer.Default).ApplyDomainSettings());
 		public static readonly IElasticClient DisabledStreaming = new ElasticClient(new TestConnectionSettings().ApplyDomainSettings().DisableDirectStreaming());
 
 		public static readonly ITestConfiguration Configuration = TestConfiguration.Instance;

src/Tests/Tests.Core/Serialization/SerializationTester.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Net;
 using System.Text;
 using Elasticsearch.Net;
 using FluentAssertions;
@@ -64,6 +65,8 @@ public class SerializationTester
 	{
 		public static SerializationTester Default { get; } = new SerializationTester(TestClient.DefaultInMemoryClient);
 
+		public static SerializationTester DefaultWithJsonNetSerializer { get; } = new SerializationTester(TestClient.InMemoryWithJsonNetSerializer);
+
 		public SerializationTester(IElasticClient client) => this.Client = client;
 
 		public IElasticClient Client { get; }

src/Tests/Tests.Reproduce/GithubIssue3356.cs

@@ -0,0 +1,36 @@
+using System;
+using Elastic.Xunit.XunitPlumbing;
+using FluentAssertions;
+using Nest;
+using Tests.Core.Extensions;
+using Tests.Core.Serialization;
+
+namespace Tests.Reproduce
+{
+	public class GithubIssue3356
+	{
+		[U]
+		public void JoinFieldDeserializedCorrectly()
+		{
+			var doc = new MyDocument
+			{
+				Join = JoinField.Root("parent")
+			};
+
+			var tester = SerializationTester.DefaultWithJsonNetSerializer;
+			var response = tester.Client.IndexDocument(doc);
+
+			tester.AssertSerialize(response.ApiCall.RequestBodyInBytes, new { join = "parent" });
+			doc = tester.AssertDeserialize<MyDocument>(response.ApiCall.RequestBodyInBytes);
+
+			doc.Join.Match(
+				p => { p.Name.Should().Be("parent"); },
+				c => throw new InvalidOperationException("should not be called"));
+		}
+
+		private class MyDocument
+		{
+			public JoinField Join { get; set; }
+		}
+	}
+}