fix(typeHelper): handle complex types

closes #137

Author: jaredcnance

src/JsonApiDotNetCore/Internal/TypeHelper.cs

@@ -7,10 +7,15 @@ public static class TypeHelper
     {
         public static object ConvertType(object value, Type type)
         {
+            if (value == null)
+                return null;
+
+            var valueType = value.GetType();
+
             try
             {
-                if (value == null)
-                    return null;
+                if (valueType == type || type.IsAssignableFrom(valueType))
+                    return value;
 
                 type = Nullable.GetUnderlyingType(type) ?? type;
 
@@ -29,7 +34,7 @@ public static object ConvertType(object value, Type type)
             }
             catch (Exception e)
             {
-                throw new FormatException($"{ value } cannot be converted to { type.GetTypeInfo().Name }", e);
+                throw new FormatException($"{ valueType } cannot be converted to { type }", e);
             }
         }
 

test/UnitTests/Internal/TypeHelper_Tests.cs

@@ -44,9 +44,59 @@ public void Can_Convert_Enums()
             Assert.Equal(TestEnum.Test, result);
         }
 
-        public enum TestEnum
+        [Fact]
+        public void ConvertType_Returns_Value_If_Type_Is_Same()
+        {
+            // arrange
+            var val = new ComplexType
+            {
+                Property = 1
+            };
+
+            var type = val.GetType();
+
+            // act
+            var result = TypeHelper.ConvertType(val, type);
+
+            // assert
+            Assert.Equal(val, result);
+        }
+
+        [Fact]
+        public void ConvertType_Returns_Value_If_Type_Is_Assignable()
+        {
+            // arrange
+            var val = new ComplexType
+            {
+                Property = 1
+            };
+
+            var baseType = typeof(BaseType);
+            var iType = typeof(IType);
+
+            // act
+            var baseResult = TypeHelper.ConvertType(val, baseType);
+            var iResult = TypeHelper.ConvertType(val, iType);
+
+            // assert
+            Assert.Equal(val, baseResult);
+            Assert.Equal(val, iResult);
+        }
+
+        private enum TestEnum
         {
             Test = 1
         }
+
+        private class ComplexType : BaseType
+        {
+            public int Property { get; set; }
+        }
+
+        private class BaseType : IType
+        { }
+
+        private interface IType
+        { }
     }
 }