Grid does not correctly notify ItemCountChangeListener if wrapped in Composite

[thomasdewaelheyns]

Description

When using a Composite, it does not correctly notify the subscribed ItemCountChangeListeners. The addItemCountChangeListener from AbstractDataView subscribes to the instance of Grid, while the fireItemCountEvent inside the DataCommunicator fires the event on the class extending the Composite. As such, no listeners are notified.

A current workaround is calling
ComponentUtil.addListener(this, ItemCountChangeEvent.class, (ComponentEventListener) event -> handleCountEvent();
from the extending class.

Expected outcome

Even when using Grid inside a composite, the ItemCountChangeListeners should be notified.

Minimal reproducible example

public ExampleGrid extends Composite<Grid<TestObject>> {
    public ExampleGrid(){
        //The below never fires
        getContent().getGenericDataView().addItemCountChangeListener(event ->
                createFooters(getContent().getGenericDataView().getItems().toList()));
        //The below is correctly notified
        ComponentUtil.addListener(this, ItemCountChangeEvent.class, (ComponentEventListener) event ->
                handleCountEvent();
    }
}

Steps to reproduce

1. Create a class extending Composite
2. In this class, add an ItemCountChangeListener
3. Make something change the item count
4. Notice that the ItemCountChangeListener is not fired.

Environment

Vaadin version(s): 24.9.10
OS: Windows 11

Browsers

Issue is not browser related

[ugur-vaadin]

The issue is reproducible using Flow-only classes.

[prasannaharrish]

@ugur-vaadin I investigated this issue and found that ItemCountChangeListener is registered on the inner Grid via AbstractDataView, while DataCommunicator.fireItemCountEvent() fires the event on the component resolved from the stateNode, which becomes the Composite instance in Composite<Grid<?>> scenarios.

Because of this mismatch, listeners registered through getGenericDataView().addItemCountChangeListener(...) are never notified.

I’d like to work on a fix for this issue if that’s okay. My current idea is to align the listener registration target with the actual event firing target used by DataCommunicator.