Add Android accessibility collection support to FlatList

packages/react-native/Libraries/Lists/FlatList.js

@@ -177,6 +177,88 @@ function isArrayLike(data: unknown): boolean {
   return typeof Object(data).length === 'number';
 }
 
+function getItemCountForAccessibility<ItemT>(
+  data: ?Readonly<$ArrayLike<ItemT>>,
+): number {
+  return data != null && isArrayLike(data) ? data.length : 0;
+}
+
+function createAccessibilityCollection<ItemT>(
+  data: ?Readonly<$ArrayLike<ItemT>>,
+  numColumns: number,
+  horizontal: boolean,
+): {
+  itemCount: number,
+  rowCount: number,
+  columnCount: number,
+  hierarchical: boolean,
+} {
+  const itemCount = getItemCountForAccessibility(data);
+  const totalCols = numColumns > 1 ? numColumns : 1;
+  if (horizontal) {
+    return {
+      itemCount,
+      rowCount: totalCols,
+      columnCount: Math.ceil(itemCount / totalCols),
+      hierarchical: false,
+    };
+  }
+  return {
+    itemCount,
+    rowCount: Math.ceil(itemCount / totalCols),
+    columnCount: totalCols,
+    hierarchical: false,
+  };
+}
+
+type AccessibilityCollectionItem = Readonly<{
+  itemIndex: number,
+  rowIndex: number,
+  rowSpan: number,
+  columnIndex: number,
+  columnSpan: number,
+  heading: boolean,
+  ...
+}>;
+
+function createAccessibilityCollectionItem(
+  itemIndex: number,
+  rowIndex: number,
+  columnIndex: number,
+  horizontal: boolean,
+): AccessibilityCollectionItem {
+  return {
+    itemIndex,
+    rowIndex: horizontal ? 0 : rowIndex,
+    rowSpan: 1,
+    columnIndex: horizontal ? itemIndex : columnIndex,
+    columnSpan: 1,
+    heading: false,
+  };
+}
+
+function addAccessibilityCollectionItem(
+  element: React.Node,
+  accessibilityCollectionItem: ?AccessibilityCollectionItem,
+): React.Node {
+  const elementForAccessibility: any = element;
+  if (
+    accessibilityCollectionItem == null ||
+    !React.isValidElement(elementForAccessibility) ||
+    elementForAccessibility.type === React.Fragment
+  ) {
+    return element;
+  }
+
+  if (elementForAccessibility.props.accessibilityCollectionItem !== undefined) {
+    return element;
+  }
+
+  return React.cloneElement(elementForAccessibility, {
+    accessibilityCollectionItem,
+  });
+}
+
 type FlatListBaseProps<ItemT> = {
   ...RequiredFlatListProps<ItemT>,
   ...OptionalFlatListProps<ItemT>,
@@ -634,29 +716,61 @@ class FlatList<ItemT = any> extends React.PureComponent<FlatListProps<ItemT>> {
     };
 
     const renderProp = (info: ListRenderItemInfo<ItemT>) => {
+      const isAndroid = Platform.OS === 'android';
+      const isHorizontal = this.props.horizontal === true;
       if (cols > 1) {
         const {item, index} = info;
         invariant(
           Array.isArray(item),
           'Expected array of items with numColumns > 1',
         );
+        const rowAccessibilityProps: any = isAndroid
+          ? ({}: any)
+          : {};
         return (
-          <View style={StyleSheet.compose(styles.row, columnWrapperStyle)}>
+          <View
+            {...rowAccessibilityProps}
+            style={StyleSheet.compose(styles.row, columnWrapperStyle)}>
             {item.map((it, kk) => {
+              const itemIndex = index * cols + kk;
+              const itemAccessibilityCollectionItem = isAndroid
+                ? createAccessibilityCollectionItem(
+                    itemIndex,
+                    index,
+                    kk,
+                    isHorizontal,
+                  )
+                : undefined;
               const element = render({
                 // $FlowFixMe[incompatible-type]
                 item: it,
-                index: index * cols + kk,
+                index: itemIndex,
                 separators: info.separators,
               });
               return element != null ? (
-                <React.Fragment key={kk}>{element}</React.Fragment>
+                <React.Fragment key={kk}>
+                  {addAccessibilityCollectionItem(
+                    element,
+                    itemAccessibilityCollectionItem,
+                  )}
+                </React.Fragment>
               ) : null;
             })}
           </View>
         );
       } else {
-        return render(info);
+        const itemAccessibilityCollectionItem = isAndroid
+          ? createAccessibilityCollectionItem(
+              info.index,
+              info.index,
+              0,
+              isHorizontal,
+            )
+          : undefined;
+        return addAccessibilityCollectionItem(
+          render(info),
+          itemAccessibilityCollectionItem,
+        );
       }
     };
 
@@ -677,11 +791,28 @@ class FlatList<ItemT = any> extends React.PureComponent<FlatListProps<ItemT>> {
     } = this.props;
 
     const renderer = strictMode ? this._memoizedRenderer : this._renderer;
+    const numColumnsValue = numColumnsOrDefault(numColumns);
+    const androidAccessibilityProps =
+      Platform.OS === 'android'
+        ? {
+            accessibilityCollection:
+              // $FlowFixMe[prop-missing] Internal native prop.
+              this.props.accessibilityCollection ??
+              createAccessibilityCollection(this.props.data, numColumnsValue, this.props.horizontal === true),
+            accessibilityRole:
+              this.props.role == null && this.props.accessibilityRole == null
+                ? numColumnsValue > 1
+                  ? 'grid'
+                  : 'list'
+                : this.props.accessibilityRole,
+          }
+        : {};
 
     return (
       // $FlowFixMe[incompatible-exact] - `restProps` (`Props`) is inexact.
       <VirtualizedList
         {...restProps}
+        {...androidAccessibilityProps}
         getItem={this._getItem}
         getItemCount={this._getItemCount}
         keyExtractor={this._keyExtractor}

packages/react-native/Libraries/Lists/__tests__/FlatList-itest.js

@@ -16,9 +16,38 @@ import * as Fantom from '@react-native/fantom';
 import nullthrows from 'nullthrows';
 import * as React from 'react';
 import {createRef} from 'react';
-import {FlatList, Text, View} from 'react-native';
+import {FlatList, Platform, Text, View} from 'react-native';
 import ReactNativeElement from 'react-native/src/private/webapis/dom/nodes/ReactNativeElement';
 
+// Object-valued props are serialized to a JSON string by the native Fantom
+// renderer, so we defensively parse them back into objects.
+// $FlowFixMe[unclear-type] parseCollectionProp returns a loosely-typed object.
+function parseCollectionProp(value: unknown): any {
+  if (typeof value === 'string') {
+    return JSON.parse(value);
+  }
+  return value;
+}
+
+// $FlowFixMe[unclear-type] collectItems walks a dynamically-typed tree.
+function collectItems(node: unknown, acc: Array<any> = []): Array<any> {
+  if (node == null || typeof node === 'string') {
+    return acc;
+  }
+  // $FlowFixMe[unclear-type] Fantom nodes have a dynamic shape.
+  const n: any = node;
+  const item = n.props != null ? n.props.accessibilityCollectionItem : null;
+  if (item != null) {
+    acc.push(parseCollectionProp(item));
+  }
+  if (Array.isArray(n.children)) {
+    n.children.forEach(child => {
+      collectItems(child, acc);
+    });
+  }
+  return acc;
+}
+
 function testPropPropagatedToMountingLayer<TValue>({
   propName,
   value,
@@ -102,6 +131,102 @@ describe('<FlatList>', () => {
       });
     });
 
+    it('adds Android accessibility collection metadata to list items', () => {
+      const originalPlatform = Platform.OS;
+      // $FlowFixMe[incompatible-type] Platform.OS is read-only in production.
+      Platform.OS = 'android';
+      try {
+        const root = Fantom.createRoot();
+        Fantom.runTask(() => {
+          root.render(
+            <FlatList
+              data={[{key: 'i1'}, {key: 'i2'}, {key: 'i3'}]}
+              renderItem={({item}) => <Text>{item.key}</Text>}
+            />,
+          );
+        });
+
+        const list = root
+          .getRenderedOutput({
+            props: ['accessibilityRole', 'accessibilityCollection'],
+          })
+          .toJSONObject();
+        expect(list.props.accessibilityRole).toBe('list');
+        expect(parseCollectionProp(list.props.accessibilityCollection)).toEqual(
+          {
+            itemCount: 3,
+            rowCount: 3,
+            columnCount: 1,
+            hierarchical: false,
+          },
+        );
+
+        const items = collectItems(
+          root
+            .getRenderedOutput({props: ['accessibilityCollectionItem']})
+            .toJSONObject(),
+        );
+        expect(items.map(i => i.itemIndex).sort((a, b) => a - b)).toEqual([
+          0, 1, 2,
+        ]);
+      } finally {
+        // $FlowFixMe[incompatible-type] Platform.OS is read-only in production.
+        Platform.OS = originalPlatform;
+      }
+    });
+
+    it('adds Android accessibility collection metadata to multi-column list items', () => {
+      const originalPlatform = Platform.OS;
+      // $FlowFixMe[incompatible-type] Platform.OS is read-only in production.
+      Platform.OS = 'android';
+      try {
+        const root = Fantom.createRoot();
+        Fantom.runTask(() => {
+          root.render(
+            <FlatList
+              data={[
+                {key: 'i1'},
+                {key: 'i2'},
+                {key: 'i3'},
+                {key: 'i4'},
+                {key: 'i5'},
+              ]}
+              renderItem={({item}) => <Text>{item.key}</Text>}
+              numColumns={2}
+            />,
+          );
+        });
+
+        const list = root
+          .getRenderedOutput({
+            props: ['accessibilityRole', 'accessibilityCollection'],
+          })
+          .toJSONObject();
+        expect(list.props.accessibilityRole).toBe('grid');
+        expect(parseCollectionProp(list.props.accessibilityCollection)).toEqual(
+          {
+            itemCount: 5,
+            rowCount: 3,
+            columnCount: 2,
+            hierarchical: false,
+          },
+        );
+
+        const items = collectItems(
+          root
+            .getRenderedOutput({props: ['accessibilityCollectionItem']})
+            .toJSONObject(),
+        );
+        expect(items.map(i => i.itemIndex).sort((a, b) => a - b)).toEqual([
+          0, 1, 2, 3, 4,
+        ]);
+        expect(items.some(i => i.columnIndex === 1)).toBe(true);
+      } finally {
+        // $FlowFixMe[incompatible-type] Platform.OS is read-only in production.
+        Platform.OS = originalPlatform;
+      }
+    });
+
     describe('inverted', () => {
       it('changes prop isInvertedVirtualizedList which gets propagated to mounting layer', () => {
         const root = Fantom.createRoot();