Add non-generic AutoMap overload

This commit adds a non-generic overload for automapping.

Closes #2907

(cherry picked from commit e818092)

Author: russcam

src/Nest/CrossPlatform/TypeExtensions.cs

@@ -56,7 +56,16 @@ internal static bool IsValue(this Type type)
 #if DOTNETCORE
 			return type.GetTypeInfo().IsValueType;
 #else
-		return type.IsValueType;
+			return type.IsValueType;
+#endif
+		}
+
+		internal static bool IsClass(this Type type)
+		{
+#if DOTNETCORE
+			return type.GetTypeInfo().IsClass;
+#else
+			return type.IsClass;
 #endif
 		}
 

src/Nest/Mapping/TypeMapping.cs

@@ -106,6 +106,19 @@ public class TypeMappingDescriptor<T> : DescriptorBase<TypeMappingDescriptor<T>,
 		public TypeMappingDescriptor<T> AutoMap(IPropertyVisitor visitor = null, int maxRecursion = 0) =>
 			Assign(a => a.Properties = a.Properties.AutoMap<T>(visitor, maxRecursion));
 
+		/// <summary>
+		/// Convenience method to map as much as it can based on <see cref="ElasticsearchTypeAttribute"/> attributes set on the type.
+		/// This particular overload is useful for automapping any children
+		/// <pre>This method also automatically sets up mappings for known values types (int, long, double, datetime, etc)</pre>
+		/// <pre>Class types default to object and Enums to int</pre>
+		/// <pre>Later calls can override whatever is set is by this call.</pre>
+		/// </summary>
+		public TypeMappingDescriptor<T> AutoMap(Type documentType, IPropertyVisitor visitor = null, int maxRecursion = 0)
+		{
+			if (!documentType.IsClass()) throw new ArgumentException("must be a reference type", nameof(documentType));
+			return Assign(a => a.Properties = a.Properties.AutoMap(documentType, visitor, maxRecursion));
+		}
+
 		/// <summary>
 		/// Convenience method to map as much as it can based on <see cref="ElasticsearchTypeAttribute"/> attributes set on the type.
 		/// This particular overload is useful for automapping any children

src/Nest/Mapping/Types/Properties.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
+using System.Reflection;
 using Elasticsearch.Net;
 using Newtonsoft.Json;
 
@@ -152,11 +153,10 @@ private PropertiesDescriptor<T> SetProperty(IProperty type)
 
 	internal static class PropertiesExtensions
 	{
-		internal static IProperties AutoMap<T>(this IProperties existingProperties, IPropertyVisitor visitor = null, int maxRecursion = 0)
-			where T : class
+		internal static IProperties AutoMap(this IProperties existingProperties, Type documentType, IPropertyVisitor visitor = null, int maxRecursion = 0)
 		{
 			var properties = new Properties();
-			var autoProperties = new PropertyWalker(typeof(T), visitor, maxRecursion).GetProperties();
+			var autoProperties = new PropertyWalker(documentType, visitor, maxRecursion).GetProperties();
 			foreach (var autoProperty in autoProperties)
 				properties[autoProperty.Key] = autoProperty.Value;
 
@@ -168,5 +168,8 @@ internal static IProperties AutoMap<T>(this IProperties existingProperties, IPro
 
 			return properties;
 		}
+
+		internal static IProperties AutoMap<T>(this IProperties existingProperties, IPropertyVisitor visitor = null, int maxRecursion = 0)
+			where T : class => existingProperties.AutoMap(typeof(T), visitor, maxRecursion);
 	}
 }