flutter_flutter/packages/flutter/test/widgets/multichildobject_with_keys_test.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';

void main() {
  testWidgets('Render and element tree stay in sync when keyed children move around', (
    WidgetTester tester,
  ) async {
    // Regression test for https://github.com/flutter/flutter/issues/48855.

    await tester.pumpWidget(
      const Directionality(
        textDirection: TextDirection.ltr,
        child: Column(
          children: <Widget>[
            Text('0', key: ValueKey<int>(0)),
            Text('1', key: ValueKey<int>(1)),
            Text('2', key: ValueKey<int>(2)),
            Text('3', key: ValueKey<int>(3)),
            Text('4', key: ValueKey<int>(4)),
            Text('5', key: ValueKey<int>(5)),
            Text('6', key: ValueKey<int>(6)),
            Text('7', key: ValueKey<int>(7)),
            Text('8', key: ValueKey<int>(8)),
          ],
        ),
      ),
    );

    expect(_getChildOrder(tester.renderObject<RenderFlex>(find.byType(Column))), <String>[
      '0',
      '1',
      '2',
      '3',
      '4',
      '5',
      '6',
      '7',
      '8',
    ]);

    await tester.pumpWidget(
      const Directionality(
        textDirection: TextDirection.ltr,
        child: Column(
          children: <Widget>[
            Text('0', key: ValueKey<int>(0)),
            Text('6', key: ValueKey<int>(6)),
            Text('7', key: ValueKey<int>(7)),
            Text('8', key: ValueKey<int>(8)),
            Text('1', key: ValueKey<int>(1)),
            Text('2', key: ValueKey<int>(2)),
            Text('3', key: ValueKey<int>(3)),
            Text('4', key: ValueKey<int>(4)),
            Text('5', key: ValueKey<int>(5)),
          ],
        ),
      ),
    );

    expect(_getChildOrder(tester.renderObject<RenderFlex>(find.byType(Column))), <String>[
      '0',
      '6',
      '7',
      '8',
      '1',
      '2',
      '3',
      '4',
      '5',
    ]);
  });

  testWidgets(
    'Building a new MultiChildRenderObjectElement with children having duplicated keys throws',
    (WidgetTester tester) async {
      const duplicatedKey = ValueKey<int>(1);

      await tester.pumpWidget(
        const Column(
          children: <Widget>[
            Text('Text 1', textDirection: TextDirection.ltr, key: duplicatedKey),
            Text('Text 2', textDirection: TextDirection.ltr, key: duplicatedKey),
          ],
        ),
      );

      expect(
        tester.takeException(),
        isA<FlutterError>().having(
          (FlutterError error) => error.message,
          'error.message',
          startsWith('Duplicate keys found.'),
        ),
      );
    },
  );

  testWidgets(
    'Updating a MultiChildRenderObjectElement to have children with duplicated keys throws',
    experimentalLeakTesting: LeakTesting.settings
        .withIgnoredAll(), // leaking by design because of exception
    (WidgetTester tester) async {
      // Regression test for https://github.com/flutter/flutter/issues/81541

      const key1 = ValueKey<int>(1);
      const key2 = ValueKey<int>(2);

      Future<void> buildWithKey(Key key) {
        return tester.pumpWidget(
          Column(
            children: <Widget>[
              const Text('Text 1', textDirection: TextDirection.ltr, key: key1),
              Text('Text 2', textDirection: TextDirection.ltr, key: key),
            ],
          ),
        );
      }

      // Initial build with two different keys.
      await buildWithKey(key2);
      expect(tester.takeException(), isNull);

      // Subsequent build with duplicated keys.
      await buildWithKey(key1);
      expect(
        tester.takeException(),
        isA<FlutterError>().having(
          (FlutterError error) => error.message,
          'error.message',
          startsWith('Duplicate keys found.'),
        ),
      );
    },
  );
}

// Do not use tester.renderObjectList(find.byType(RenderParagraph). That returns
// the RenderObjects in the order of their associated RenderObjectWidgets. The
// point of this test is to assert the children order in the render tree, though.
List<String> _getChildOrder(RenderFlex flex) {
  final childOrder = <String>[];
  flex.visitChildren((RenderObject child) {
    childOrder.add(((child as RenderParagraph).text as TextSpan).text!);
  });
  return childOrder;
}