Using JSON.stringify with an ExpandoObject returns "{}" instead of useful results

[craigfowler]

I have created a small repo which contains a reproduction case for this. To see the issue for yourself clone it and run it using dotnet test. This might be a duplicate of #347, although I want to specifically point out the behaviour relating to ExpandoObject instead of a statically-typed class instance.

If an ExpandoObject is added into a Jint environment via SetValue & subsequently an attempt is made to JSON.stringify(theExpando), this will always produce a result of "{}". Instead I think it should produce appropriate results for the state of that expando object.

This is particularly troublesome because of the behaviour of JSON.parse. When using JSON.parse('{"foo":5,"bar":"A string"}'), Jint will return an expando back to "the .NET world". That's understandable; I don't think any other behaviour would make any sense. Unfortunately, that returned object then can't be round-tripped back to JSON by executing JS via Jint, because of this issue.

[craigfowler]

I forgot to mention, one of the test cases in the repro repository does pass. It shows how it stringifies correctly if you give Jint a Dictionary<string,object>. It's possible to convert expandos to that, so that might be a viable workaround for those who run into this.

[ayende]

Note that this means that Jint will have to understand IDynamicObject to support this.