Avoid unnecessary conversion of JsonValue objects

[dpolysiou]

When returning JSON scalar data from a field, we can return the JsonValue object as is, without recursively traversing the pojo.

This makes a difference when the field payload is large, as it avoids performing unnecessary work on the event loop thread. Here is an example where an unreasonably large field leads to blocking the event loop thread.

[jmartisk]

If you look a few lines below, we have some more customized logic for processing the object, like acting on the isExcludeNullFieldsInResponses configuration field, will this not break that functionality? I guess you would skip the removal of nulls from the response if isExcludeNullFieldsInResponses==true with this code.

Perhaps a good solution would be to leave it to the original custom logic if isExcludeNullFieldsInResponses==true (or even better, implement a faster version of it specifically for JsonValue that would only remove nulls, but that's optional for now) and do your thing of returning the JsonValue directly only if isExcludeNullFieldsInResponses==false?

[dpolysiou]

I added a method similar to the handling of Map that produces a copy of the JsonValue, with null fields excluded. I hope that's fine.

[jmartisk]

Thanks!