fix: focus selected item with wrapped in-memory data providers (#9396)

A `ComboBox` with `setFocusSelectedItem(true)` throws a
`ClassCastException` when opening the dropdown if its items come from a
`ListDataProvider` wrapped with `withConvertedFilter(...)`.
`scrollToSelectedItem()` resolved the selected item's index through the
list data view, which casts the provider to `ListDataProvider`. The
wrapper is in-memory but not a `ListDataProvider`, so the cast fails.

```java
ComboBox<String> comboBox = new ComboBox<>();
ListDataProvider<String> dataProvider = DataProvider
        .ofCollection(List.of("A", "B", "C", "D"));
comboBox.setItems(dataProvider.withConvertedFilter(
        filterText -> item -> item.contains(filterText)));
comboBox.setFocusSelectedItem(true);
comboBox.setValue("C");
comboBox.setOpened(true); // throws ClassCastException
```

`scrollToSelectedItem()` now resolves the index through the generic data
view (`ComboBoxDataView`) for in-memory providers instead of the list
data view. The generic data view reads items from the data communicator
and works for any in-memory provider, wrapped or not, so the list data
view is no longer used for providers that aren't a `ListDataProvider`.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: DiegoCardoso

vaadin-combo-box-flow-parent/vaadin-combo-box-flow/src/main/java/com/vaadin/flow/component/combobox/ComboBox.java

@@ -422,7 +422,12 @@ private void scrollToSelectedItem() {
         }
         Integer index;
         if (dataProvider.isInMemory()) {
-            index = getListDataView().getItemIndex(getValue()).orElse(null);
+            // Use the generic data view rather than the list data view: it
+            // resolves the item index through the data communicator and works
+            // for any in-memory provider, including wrapped ones (e.g. from
+            // ListDataProvider.withConvertedFilter) that are not a
+            // ListDataProvider and would fail the list data view's cast.
+            index = getGenericDataView().getItemIndex(getValue()).orElse(null);
         } else {
             index = getLazyDataView().getItemIndex(getValue()).orElse(null);
         }

vaadin-combo-box-flow-parent/vaadin-combo-box-flow/src/test/java/com/vaadin/flow/component/combobox/ComboBoxTest.java

@@ -16,6 +16,7 @@
 package com.vaadin.flow.component.combobox;
 
 import java.util.Arrays;
+import java.util.List;
 import java.util.stream.Stream;
 
 import org.junit.jupiter.api.Assertions;
@@ -29,9 +30,12 @@
 import com.vaadin.flow.component.Tag;
 import com.vaadin.flow.component.Text;
 import com.vaadin.flow.component.Unit;
+import com.vaadin.flow.component.internal.PendingJavaScriptInvocation;
 import com.vaadin.flow.component.shared.HasThemeVariant;
 import com.vaadin.flow.component.shared.InputField;
 import com.vaadin.flow.data.binder.Binder;
+import com.vaadin.flow.data.provider.DataProvider;
+import com.vaadin.flow.data.provider.ListDataProvider;
 import com.vaadin.flow.di.Instantiator;
 import com.vaadin.flow.dom.Element;
 
@@ -253,6 +257,31 @@ void setFocusSelectedItem_isFocusSelectedItem() {
         Assertions.assertFalse(comboBox.isFocusSelectedItem());
     }
 
+    @Test
+    void focusSelectedItem_convertedFilterListDataProvider_scrollsToSelectedItem() {
+        // withConvertedFilter wraps the ListDataProvider in a provider that is
+        // in-memory but not a ListDataProvider. Opening the dropdown must
+        // resolve the selected item's index without failing.
+        ComboBox<String> comboBox = new ComboBox<>();
+        ui.add(comboBox);
+        ListDataProvider<String> dataProvider = DataProvider
+                .ofCollection(List.of("A", "B", "C", "D"));
+        comboBox.setItems(dataProvider.withConvertedFilter(
+                filterText -> item -> item.contains(filterText)));
+        comboBox.setFocusSelectedItem(true);
+        comboBox.setValue("C");
+        comboBox.setOpened(true);
+
+        var invocations = ui.dumpPendingJavaScriptInvocations().stream()
+                .map(PendingJavaScriptInvocation::getInvocation)
+                .filter(invocation -> invocation.getExpression()
+                        .contains("scrollToIndex"))
+                .toList();
+        Assertions.assertEquals(1, invocations.size());
+        // Parameter 0 is the target element, parameter 1 is the item index
+        Assertions.assertEquals(2, invocations.get(0).getParameters().get(1));
+    }
+
     @Test
     void setFilterTimeout_getFilterTimeout() {
         ComboBox<String> comboBox = new ComboBox<>();