MapFromAttributes() now throws if an ElasticProperty is set on a value type it can not infer a FieldType for and none is set either

Author: Mpdreamz

src/Nest/Resolvers/Writers/TypeMappingWriter.cs

@@ -15,6 +15,10 @@ public class TypeMappingWriter
 		private readonly Type _type;
 		private readonly IConnectionSettingsValues _connectionSettings;
 		private readonly NestSerializer _elasticSerializer;
+
+		private readonly static string _noFieldTypeMessage =
+			"Property {0} on type {1} has an ElasticProperty attribute but its FieldType (Type = ) can not be inferred and is not set explicitly while calling MapFromAttributes";
+
 		private ElasticInferrer Infer { get; set; }
 
 		private int MaxRecursion { get; set; }
@@ -194,6 +198,11 @@ private string GetElasticSearchType(IElasticPropertyAttribute att, PropertyInfo
 			if (fieldType == null || fieldType == FieldType.None)
 			{
 				fieldType = this.GetFieldTypeFromType(p.PropertyType);
+				if (fieldType == null && att != null)
+				{
+					var message = _noFieldTypeMessage.F(p.Name, this._type.Name);
+					throw new DslException(message);
+				}
 			}
 
 			return this.GetElasticSearchTypeFromFieldType(fieldType);

src/Tests/Nest.Tests.Unit/Core/Map/Structs/EnumMappingTests.cs

@@ -0,0 +1,62 @@
+using NUnit.Framework;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Text;
+using System.Threading.Tasks;
+using FluentAssertions;
+
+namespace Nest.Tests.Unit.Core.Map.Structs
+{
+	[TestFixture]
+	public class StructMappingTests : BaseJsonTests
+	{
+		private class MyClass
+		{
+			public MyStruct Struct { get; set; }
+		}
+
+		private class MyClass2
+		{
+			[ElasticProperty(Analyzer = "default")]
+			public MyStruct StructProperty { get; set; }
+		}
+
+		private struct MyStruct
+		{
+			public string Object { get; set; }
+		}
+
+		[Test]
+		public void StructWithNoAttributeSetIsIgnored()
+		{
+			//unknow value types are not handled by default by MapFromAttributes()
+			var result = this._client.Map<MyClass>(m => m.MapFromAttributes());
+			this.JsonEquals(result.ConnectionStatus.Request, MethodBase.GetCurrentMethod());
+		}
+
+		[Test]
+		public void StructWithAttributeButNoTypeInformationThrows()
+		{
+			//unknown value types with missing FieldType information in the attribute should throw an exception
+			
+			//example
+
+			//Nest.DslException : Property Struct on type MyClass2 <continued>
+			//has an ElasticProperty attribute but its FieldType (Type = ) can not be inferred <continued>
+			//and is not set explicitly while calling MapFromAttributes
+
+			var e = Assert.Throws<DslException>(() =>
+			{
+				var result = this._client.Map<MyClass2>(m => m.MapFromAttributes());
+				this.JsonEquals(result.ConnectionStatus.Request, MethodBase.GetCurrentMethod());
+			});
+
+			e.Message.Should().EndWith("while calling MapFromAttributes");
+			e.Message.Should().Contain("StructProperty");
+		}
+
+	}
+
+}

src/Tests/Nest.Tests.Unit/Core/Map/Structs/StructWithAttributeButNoTypeInformationThrows.json

@@ -0,0 +1,6 @@
+{
+  "myclass2": {
+    "properties": {
+    }
+  }
+}

src/Tests/Nest.Tests.Unit/Core/Map/Structs/StructWithNoAttributeSetIsIgnored.json

@@ -0,0 +1,6 @@
+{
+  "myclass": {
+    "properties": {
+    }
+  }
+}