Bug 4230

Summary: DataContractJsonSerializer mishandles deserialization of null arrays
Product: iOS Reporter: Steve Gordon <steveg>
Component: BCL Class LibrariesAssignee: Alexander Köplinger [MSFT] <alkpli>
Status: RESOLVED FIXED    
Severity: normal CC: kumpera, marcos.henrich, masafa, mono-bugs+monotouch
Priority: ---    
Version: 5.0   
Target Milestone: Untriaged   
Hardware: PC   
OS: Mac OS   
Tags: Is this bug a regression?: ---
Last known good build:

Description Steve Gordon 2012-04-04 10:34:23 UTC
In porting existing .NET / Windows Phone code, I discovered a behavior of DataContractJsonSerializer in MonoTouch that is inconsistent with other platforms.

Specifically, when deserializing JSON where an array property has a null value, DataContractJsonSerializer incorrectly maps the null value to an empty array. This is problematic because it causes you to lose the ability to differentiate between null and empty.

For example, given the below class and JSON:

class:

public class Response
{
  public Notification[] Notifications
  {
    get;
    set;
  }
}

JSON:

{
  Notifications: null,
}

With MonoTouch, Notifications is set to Notification[0], whereas on other platforms, Notifications is correctly set to null.
Comment 1 Rodrigo Kumpera 2015-10-30 09:36:09 UTC
Hey Alex,

Could you look at this one?
Comment 2 Alexander Köplinger [MSFT] 2015-10-30 20:17:52 UTC
I confirmed it reproduces on Mono 4.0. It's fixed in Mono 4.2 because we moved to Reference Sources.

Curiously, while looking at it I was somewhat confused cause we still had a copy of DataContractJsonSerializer in System.ServiceModel.Web that's not used anymore. I opened https://github.com/mono/mono/pull/2185 to cleanup those and added the test from this bug while I was at it.