OnDetach will not be called on page reload

Description of the bug

The documentation states

The onAttach() method is invoked when the Component has attached to the UI. Its counterpart, the onDetach() method, is invoked right before the component detaches from the UI. These are good points at which to reserve and release resources used by the component.

This is what I did. Sadly, the onDetach() method is not called if a user decides to reload the page. Thus, all resources acquired during onAttach() leak.

Expected behavior

onDetach() will always be called if the component is detached - regardless the reason.

Minimal reproducible example

public class TestClass extends Component {

   @Override
   protected void onAttach(AttachEvent attachEvent) {
      super.onAttach(attachEvent);
      System.out.println("Calling onAttach");
   }

   @Override
   protected void onDetach(DetachEvent detachEvent) {
      super.onDetach(detachEvent);
      System.out.println("Calling onDetach");
   }
}

Versions

• Vaadin / Flow version:
• Java version: kotlin with JDK 17
• OS version: Arch Linux (current)
• Browser version (if applicable): Firefox 97

[Artur-]

To be clear, onDetach is always called and the API contract is not broken. It is called way later than you would expect though (when the session expires).

No matter if we call this enhancement or bug or anything else, I think it should be improved (fixed). For instance by integrating the mentioned cookbook recipe.

[tarekoraby]

There is a workaround based on Beacon API documented at https://cookbook.vaadin.com/notice-closed.