Enum deserialization exception is not very helpful #1614
Description
Expected Behavior
For a response where the following class is serialized:
public class Config
{
public List<Option> Options { get; set; }
}
With server-side code:
public enum Option
{
Zero,
One,
Two,
Three
};
And a client-side bug:
public enum Option
{
Zero,
One,
Two
// Three is missing
};
I would hope to get a meaningful exception.
Actual Behavior
The exception tells me about the internals of RestSharp, not about the type being deserialized:
Value cannot be null.
Parameter name: item
Specifications
- Version: Any recent version including 106.12.0 and dev branch
- Platform: Windows 10
StackTrace
System.ArgumentNullException
at System.ThrowHelper.IfNullAndNullsAreIllegalThenThrow[T](Object value, ExceptionArgument argName)
at System.Collections.Generic.List`1.System.Collections.IList.Add(Object item)
at RestSharp.Serialization.Json.JsonSerializer.BuildList(Type type, Object parent)
at RestSharp.Serialization.Json.JsonSerializer.ConvertValue(TypeInfo typeInfo, Object value)
at RestSharp.Serialization.Json.JsonSerializer.Map(Object target, IDictionary`2 data)
at RestSharp.Serialization.Json.JsonSerializer.CreateAndMap(Type type, Object element)
at RestSharp.Serialization.Json.JsonSerializer.ConvertValue(TypeInfo typeInfo, Object value)
at RestSharp.Serialization.Json.JsonSerializer.Deserialize[T](IRestResponse response)
at RestSharp.RestClient.Deserialize[T](IRestRequest request, IRestResponse raw)
So the code path is:
\RestSharp\src\RestSharp\Serializers\Json\JsonSerializer.cs
IList BuildList(Type type, object? parent) {
// ...
var item = ConvertValue(itemType.GetTypeInfo(), element);
list.Add(item); // ** Thrown here because item is null. **
\RestSharp\src\RestSharp\Serializers\Json\JsonSerializer.cs
object? ConvertValue(TypeInfo typeInfo, object? value) {
// ...
if (typeInfo.IsEnum) return type.FindEnumValue(stringValue, Culture);
\RestSharp\src\RestSharp\Extensions\ReflectionExtensions.cs
public static object? FindEnumValue(this Type type, string value, CultureInfo culture)
// ...
return ret; // ** Returns the null which will cause the exception **
Possible fix
It would be nice to return information that the caller could use to identify the problem. Different info is available at different levels in the stack, and devs more familiar with the RestSharp codebase could craft something elegant. But the simplest change would seem to be something like a null check at the end of FindEnumValue():
if (ret == null)
throw new ArgumentOutOfRangeException(value + " undefined for " + type);
return ret;
Which gives an exception message such as:
Exception: Specified argument was out of the range of valid values.
Parameter name: 3 undefined for Option
I can submit this as a PR if desired, though it's trivial and you'll likely want to change something.