Cannot warn or use the previous DNodes when a supported DNode type of undefined is returned.

[agubler]

Type: feature

The following has been addressed in the PR:

• There is a related issue
• All code matches the style guide
• Unit or Functional tests are included in the PR

Description:

It was fine to warn when undefined was not a supported DNode value but now that undefined is a supported type, we cannot warn or automatically replace with the previous value.

Resolves #585

[kitsonk]

Is it a valid/legitimate use case that the original DNode was of a value, but the return type is actually undefined? Ergo, could it be done in cases where the previous !== undefined && current === undefined?

Tangental to this, but related, would it make sense at the decorator API to allowing passing of an optional argument that was something like observe: boolean which would always ignore what is returned (and would even have an overload of (callback: (...) => void, observe: true)?

I think just "observing" the render is a legitimate use case. You want to watch but you want to contract to not modify the render.

[agubler]

Is it a valid/legitimate use case that the original DNode was of a value, but the return type is actually undefined? Ergo, could it be done in cases where the previous !== undefined && current === undefined?

Okay, so I originally did this - however this would mean that if the afterRender legitimately returned undefined it would use the previous dNode value - this doesn't seem correct.

I think just "observing" the render is a legitimate use case. You want to watch but you want to contract to not modify the render.

Personally think that the afterRender is only there to work with the decorating the dNodes, not to add any side affect like storing state.

[kitsonk]

Personally think that the afterRender is only there to work with the decorating the dNodes, not to add any side affect like storing state.

👍 Ok, if we find a legitimate use case for just being able to get notified of when something renders, we can revisit. I will admit everything I have seen to date is some sort of hack for something we wanted to support in another way.