Fix invariant violation when nesting VirtualizedList inside ListEmpty…

…Component (#35875)

Summary:
Pull Request resolved: #35875

Fixes #35871

Nested VirtualizedLists register to their parents for updates, associated to a specfific cellKey set by VirtualizedListCellContextProvider. This cellKey is usually set when rendering a cell for a data item, but we can also render a nested VirtualizedList by putting one in a ListHeaderComponent/ListFooterComponent/ListEmptyComponent.

D6603342 (a010a0c) added cellKeys when we render from a header/footer, but not ListEmptyComponent, so that association would silently fail earlier.

D39466677 (010da67) added extra invariants to child list handling, that are now triggered by this case, complaining because we are trying to unregister a child list we never successfully registered, due to a missing cellKey.

This fixes the issue by providing a cellKey for ListEmptyComponent as well.

Changelog:
[General][Fixed] - Fix invariant violation when nesting VirtualizedList inside ListEmptyComponent

Reviewed By: christophpurrer

Differential Revision: D42574462

fbshipit-source-id: f76fa795bf471cb8a929c2efdbd814ea51927663

# Conflicts:
#	Libraries/Lists/VirtualizedList.js

Libraries/Lists/VirtualizedList.js

@@ -860,16 +860,19 @@ export default class VirtualizedList extends StateSafePureComponent<
         <ListEmptyComponent />
       )): any);
       cells.push(
-        React.cloneElement(element, {
-          key: '$empty',
-          onLayout: event => {
-            this._onLayoutEmpty(event);
-            if (element.props.onLayout) {
-              element.props.onLayout(event);
-            }
-          },
-          style: StyleSheet.compose(inversionStyle, element.props.style),
-        }),
+        <VirtualizedListCellContextProvider
+          cellKey={this._getCellKey() + '-empty'}
+          key="$empty">
+          {React.cloneElement(element, {
+            onLayout: (event: LayoutEvent) => {
+              this._onLayoutEmpty(event);
+              if (element.props.onLayout) {
+                element.props.onLayout(event);
+              }
+            },
+            style: StyleSheet.compose(inversionStyle, element.props.style),
+          })}
+        </VirtualizedListCellContextProvider>,
       );
     }
 

Libraries/Lists/__tests__/VirtualizedList-test.js

@@ -245,6 +245,32 @@ describe('VirtualizedList', () => {
     expect(component).toMatchSnapshot();
   });
 
+  it('handles nested list in ListEmptyComponent', () => {
+    const ListEmptyComponent = (
+      <VirtualizedList {...baseItemProps(generateItems(1))} />
+    );
+
+    let component;
+
+    ReactTestRenderer.act(() => {
+      component = ReactTestRenderer.create(
+        <VirtualizedList
+          {...baseItemProps([])}
+          ListEmptyComponent={ListEmptyComponent}
+        />,
+      );
+    });
+
+    ReactTestRenderer.act(() => {
+      component.update(
+        <VirtualizedList
+          {...baseItemProps(generateItems(5))}
+          ListEmptyComponent={ListEmptyComponent}
+        />,
+      );
+    });
+  });
+
   it('returns the viewableItems correctly in the onViewableItemsChanged callback after changing the data', () => {
     const ITEM_HEIGHT = 800;
     let data = [{key: 'i1'}, {key: 'i2'}, {key: 'i3'}];