feat(#139): handle empty strings in type helper

Author: jaredcnance

src/JsonApiDotNetCore/Internal/TypeHelper.cs

@@ -21,6 +21,9 @@ public static object ConvertType(object value, Type type)
 
                 var stringValue = value.ToString();
 
+                if (string.IsNullOrEmpty(stringValue))
+                    return GetDefaultType(type);
+
                 if (type == typeof(Guid))
                     return Guid.Parse(stringValue);
 
@@ -38,6 +41,15 @@ public static object ConvertType(object value, Type type)
             }
         }
 
+        private static object GetDefaultType(Type type)
+        {
+            if (type.GetTypeInfo().IsValueType)
+            {
+                return Activator.CreateInstance(type);
+            }
+            return null;
+        }
+
         public static T ConvertType<T>(object value)
         {
             return (T)ConvertType(value, typeof(T));

test/UnitTests/Internal/TypeHelper_Tests.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using JsonApiDotNetCore.Internal;
 using Xunit;
 
@@ -83,6 +84,29 @@ public void ConvertType_Returns_Value_If_Type_Is_Assignable()
             Assert.Equal(val, iResult);
         }
 
+        [Fact]
+        public void ConvertType_Returns_Default_Value_For_Empty_Strings()
+        {
+            // arrange -- can't use non-constants in [Theory]
+            var data = new Dictionary<Type, object>
+            {
+                { typeof(int), 0 },
+                { typeof(short), (short)0 },
+                { typeof(long), (long)0 },
+                { typeof(string), "" },
+                { typeof(Guid), Guid.Empty },
+            };
+
+            foreach (var t in data)
+            {
+                // act
+                var result = TypeHelper.ConvertType(string.Empty, t.Key);
+
+                // assert
+                Assert.Equal(t.Value, result);
+            }
+        }
+
         private enum TestEnum
         {
             Test = 1