1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
// 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/widgets.dart';
import 'package:flutter_test/flutter_test.dart';
// This is a regression test for https://github.com/flutter/flutter/issues/5588.
class OrderSwitcher extends StatefulWidget {
const OrderSwitcher({
super.key,
required this.a,
required this.b,
});
final Widget a;
final Widget b;
@override
OrderSwitcherState createState() => OrderSwitcherState();
}
class OrderSwitcherState extends State<OrderSwitcher> {
bool _aFirst = true;
void switchChildren() {
setState(() {
_aFirst = false;
});
}
@override
Widget build(BuildContext context) {
return Stack(
textDirection: TextDirection.ltr,
children: _aFirst
? <Widget>[
KeyedSubtree(child: widget.a),
widget.b,
]
: <Widget>[
KeyedSubtree(child: widget.b),
widget.a,
],
);
}
}
class DummyStatefulWidget extends StatefulWidget {
const DummyStatefulWidget(Key? key) : super(key: key);
@override
DummyStatefulWidgetState createState() => DummyStatefulWidgetState();
}
class DummyStatefulWidgetState extends State<DummyStatefulWidget> {
@override
Widget build(BuildContext context) => const Text('LEAF', textDirection: TextDirection.ltr);
}
class RekeyableDummyStatefulWidgetWrapper extends StatefulWidget {
const RekeyableDummyStatefulWidgetWrapper({
super.key,
this.child,
required this.initialKey,
});
final Widget? child;
final GlobalKey initialKey;
@override
RekeyableDummyStatefulWidgetWrapperState createState() => RekeyableDummyStatefulWidgetWrapperState();
}
class RekeyableDummyStatefulWidgetWrapperState extends State<RekeyableDummyStatefulWidgetWrapper> {
GlobalKey? _key;
@override
void initState() {
super.initState();
_key = widget.initialKey;
}
void _setChild(GlobalKey? value) {
setState(() {
_key = value;
});
}
@override
Widget build(BuildContext context) {
return DummyStatefulWidget(_key);
}
}
void main() {
testWidgets('Handle GlobalKey reparenting in weird orders', (WidgetTester tester) async {
// This is a bit of a weird test so let's try to explain it a bit.
//
// Basically what's happening here is that we have a complicated tree, and
// in one frame, we change it to a slightly different tree with a specific
// set of mutations:
//
// * The keyA subtree is regrafted to be one level higher, but later than
// the keyB subtree.
// * The keyB subtree is, similarly, moved one level deeper, but earlier, than
// the keyA subtree.
// * The keyD subtree is replaced by the previously earlier and shallower
// keyC subtree. This happens during a LayoutBuilder layout callback, so it
// happens long after A and B have finished their dance.
//
// The net result is that when keyC is moved, it has already been marked
// dirty from being removed then reinserted into the tree (redundantly, as
// it turns out, though this isn't known at the time), and has already been
// visited once by the code that tries to clean nodes (though at that point
// nothing happens since it isn't in the tree).
//
// This test verifies that none of the asserts go off during this dance.
final GlobalKey<OrderSwitcherState> keyRoot = GlobalKey(debugLabel: 'Root');
final GlobalKey keyA = GlobalKey(debugLabel: 'A');
final GlobalKey keyB = GlobalKey(debugLabel: 'B');
final GlobalKey keyC = GlobalKey(debugLabel: 'C');
final GlobalKey keyD = GlobalKey(debugLabel: 'D');
await tester.pumpWidget(OrderSwitcher(
key: keyRoot,
a: KeyedSubtree(
key: keyA,
child: RekeyableDummyStatefulWidgetWrapper(
initialKey: keyC,
),
),
b: KeyedSubtree(
key: keyB,
child: Builder(
builder: (BuildContext context) {
return Builder(
builder: (BuildContext context) {
return Builder(
builder: (BuildContext context) {
return LayoutBuilder(
builder: (BuildContext context, BoxConstraints constraints) {
return RekeyableDummyStatefulWidgetWrapper(
initialKey: keyD,
);
},
);
},
);
},
);
},
),
),
));
expect(find.byKey(keyA), findsOneWidget);
expect(find.byKey(keyB), findsOneWidget);
expect(find.byKey(keyC), findsOneWidget);
expect(find.byKey(keyD), findsOneWidget);
expect(find.byType(RekeyableDummyStatefulWidgetWrapper), findsNWidgets(2));
expect(find.byType(DummyStatefulWidget), findsNWidgets(2));
keyRoot.currentState!.switchChildren();
final List<State> states = tester.stateList(find.byType(RekeyableDummyStatefulWidgetWrapper)).toList();
final RekeyableDummyStatefulWidgetWrapperState a = states[0] as RekeyableDummyStatefulWidgetWrapperState;
a._setChild(null);
final RekeyableDummyStatefulWidgetWrapperState b = states[1] as RekeyableDummyStatefulWidgetWrapperState;
b._setChild(keyC);
await tester.pump();
expect(find.byKey(keyA), findsOneWidget);
expect(find.byKey(keyB), findsOneWidget);
expect(find.byKey(keyC), findsOneWidget);
expect(find.byKey(keyD), findsNothing);
expect(find.byType(RekeyableDummyStatefulWidgetWrapper), findsNWidgets(2));
expect(find.byType(DummyStatefulWidget), findsNWidgets(2));
});
}