False cyclic dependency exceptions

[oleih]

We get false cyclic dependency exceptions (ObjectGraphDiff.cs:87).

Thrown if both left and right graph contain value type objects that hash to the same value (e.g. MongoDB.Bson.ObjectId with the same value in each graph).

Also: It is also thrown for reference types types that only contain such value types, e.g.:
public class TimeRange
{
public readonly TimeSpan Start;
public readonly TimeSpan End;
public TimeRange(string hhmmStart, string hhmmEnd)
{
//..
}
}

It would be great if it was possible to disable the cyclic dependency checking. We know that our graphs are not cyclic. :-)

Also, we think there may be a problem in ODiff.Extensions.ObjectExtensions.cs:32. Perhaps it is better to use obj is ValueType?

[goeran]

Thanks. I'll look into this over the summer.

A simple workaround would be to rewrite the object graph. Use the type interceptor and rewrite the value of the ObjectId. I'm sure the id can be presented as an string? If so I suggest you write a interceptor like this (psudo code).

var mongoDbObjectIdInterceptor = new TypeInterceptor<ObjectId>(input => input.ToString());
Diff.ObjectValues(objA, objB, mongoDbObjectIdInterceptor);

You also use other interceptors to rewrite the graph.

If you got time it would be nice if you could create a pull request with some failing tests that prove the problems you are describing. Thanks :)