[TINKERPOP-2788] Gremlin.Net incorrectly serializes custom types without type information for GraphSON 3

• Type: Bug
• Status: Open
• Priority: Trivial
• Resolution: Unresolved
• Affects Version/s: 3.6.1, 3.5.4
• Component/s: dotnet, server
• Assignee: Unassigned
• Reporter: Florian Hockmann
• Created: 01/Sep/22 15:06
• Updated: 01/Sep/22 15:06

Description

Gremlin.Net incorrectly serializes an object of a custom type for GraphSON 3 if it doesn't have a custom serializer for that type. It simply passes the object to its underlying JSON serializer which results in a JSON serialization without any type information.

I think this shouldn't be possible as we always expect types with GraphSON 3 as per the specs:

> GraphSON 3.0 does not have an option to be typeless. Types are always embedded except for strings and boolean values which are inferred from JSON types.

Example code to reproduce:

var xxx = new[] { new XXX { X = 1, Y = 2 }, new XXX { X = 3, Y = 4 } };

var graphSon = writer.WriteObject(xxx);

// graphSon = "{"@type":"g:List","@value":[{"X":1,"Y":2},{"X":3,"Y":4}]}" 

But the problem doesn't seem to be limited to .NET as the server also successfully responds to a request with such a custom type if it's used in a traversal:

var xxx = new[] { new XXX { X = 1, Y = 2 }, new XXX { X = 3, Y = 4 } };
var result = (List<object>)await g.Inject<object>(xxx).Promise(t => t.ToList());
foreach (var x in result)
{
  foreach (var pair in (Dictionary<object, object>)x)
  {
    Console.WriteLine($"{pair.Key}: {pair.Value}");
  }
}

/*… which displays:
X: 1
Y: 2
X: 3
Y: 4*/

This was first reported on the janusgraph-users mailing list by billpoole.