Flutter framework internal error thrown when removing second-to-last child of IndexedStack #165840
Description
Steps to reproduce
Happened after setting State that should cause IndexedStack to re-render and discover one less child than previous render cycle. Note that moving from 4 to 3 to 2 children this way worked fine, but reliably throws this error when moving from State that will find 2 children to State that will find one child.
Console output was:
════════ Exception caught by rendering library ═════════════════════════════════
The following assertion was thrown during paint():
'package:flutter/src/rendering/stack.dart': Failed assertion: line 799 pos 12: 'firstChild == null || child != null': is not true.
Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
https://github.com/flutter/flutter/issues/new?template=2_bug.yml
The relevant error-causing widget was:
IndexedStack IndexedStack:file:///F:/work/FractalOutliner/repo/FractalOutliner/flutter_app/fractal_outliner/lib/view/editor_stack/editor_panel_stack.dart:18:16
When the exception was thrown, this was the stack:
#2 RenderIndexedStack._childAtIndex (package:flutter/src/rendering/stack.dart:799:12)
#3 RenderIndexedStack.paintStack (package:flutter/src/rendering/stack.dart:859:39)
#4 RenderStack.paint (package:flutter/src/rendering/stack.dart:720:7)
#5 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#6 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:260:13)
#7 RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:3360:15)
#8 RenderFlex.paint (package:flutter/src/rendering/flex.dart:1315:7)
#9 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#10 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:260:13)
#11 RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:3360:15)
#12 RenderFlex.paint (package:flutter/src/rendering/flex.dart:1315:7)
#13 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#14 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:260:13)
#15 RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:3360:15)
#16 RenderStack.paintStack (package:flutter/src/rendering/stack.dart:704:5)
#17 RenderStack.paint (package:flutter/src/rendering/stack.dart:720:7)
#18 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#19 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:260:13)
#20 RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:3360:15)
#21 RenderCustomMultiChildLayoutBox.paint (package:flutter/src/rendering/custom_layout.dart:424:5)
#22 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#23 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:260:13)
#24 RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:140:13)
#25 _RenderInkFeatures.paint (package:flutter/src/material/material.dart:632:11)
#26 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#27 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:260:13)
#28 RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:140:13)
#29 RenderPhysicalModel.paint.<anonymous closure> (package:flutter/src/rendering/proxy_box.dart:2083:15)
#30 PaintingContext.pushClipRRect (package:flutter/src/rendering/object.dart:610:14)
#31 RenderPhysicalModel.paint (package:flutter/src/rendering/proxy_box.dart:2070:21)
#32 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#33 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:260:13)
#34 RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:140:13)
#35 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#36 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:260:13)
#37 RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:140:13)
#38 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:3371:7)
#39 PaintingContext._repaintCompositedChild (package:flutter/src/rendering/object.dart:175:11)
#40 PaintingContext.repaintCompositedChild (package:flutter/src/rendering/object.dart:120:5)
#41 PipelineOwner.flushPaint (package:flutter/src/rendering/object.dart:1251:31)
#42 PipelineOwner.flushPaint (package:flutter/src/rendering/object.dart:1261:15)
#43 RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:618:23)
#44 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:1231:13)
#45 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:482:5)
#46 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1442:15)
#47 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1355:9)
#48 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:1208:5)
#49 _invoke (dart:ui/hooks.dart:316:13)
#50 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:428:5)
#51 _drawFrame (dart:ui/hooks.dart:288:31)
(elided 2 frames from class _AssertionError)
The following RenderObject was being processed when the exception was fired: RenderIndexedStack#2f9cd relayoutBoundary=up4
needs compositing
parentData: offset=Offset(0.0, 35.0); flex=1; fit=FlexFit.tight (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, h=647.7)
size: Size(785.3, 647.7)
alignment: AlignmentDirectional.topStart
textDirection: ltr
fit: loose
index: 1
child 1: _RenderVisibility#c03cf relayoutBoundary=up5 NEEDS-PAINT
needs compositing
parentData: not positioned; offset=Offset(0.0, 0.0) (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, 0.0<=h<=647.7)
size: Size(785.3, 647.7)
child: RenderIgnorePointer#444c8 relayoutBoundary=up6 NEEDS-PAINT
needs compositing
parentData: <none> (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, 0.0<=h<=647.7)
size: Size(785.3, 647.7)
ignoring: false
ignoringSemantics: null
child: RenderStack#1a31a relayoutBoundary=up7 NEEDS-PAINT
needs compositing
parentData: <none> (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, 0.0<=h<=647.7)
size: Size(785.3, 647.7)
alignment: AlignmentDirectional.topStart
textDirection: ltr
fit: loose
child 1: RenderFlex#7b1b6 relayoutBoundary=up8 NEEDS-PAINT
needs compositing
parentData: not positioned; offset=Offset(0.0, 0.0) (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, 0.0<=h<=647.7)
size: Size(785.3, 647.7)
direction: horizontal
mainAxisAlignment: start
mainAxisSize: max
crossAxisAlignment: start
textDirection: ltr
verticalDirection: down
spacing: 0.0
RenderObject: RenderIndexedStack#2f9cd relayoutBoundary=up4
needs compositing
parentData: offset=Offset(0.0, 35.0); flex=1; fit=FlexFit.tight (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, h=647.7)
size: Size(785.3, 647.7)
alignment: AlignmentDirectional.topStart
textDirection: ltr
fit: loose
index: 1
child 1: _RenderVisibility#c03cf relayoutBoundary=up5 NEEDS-PAINT
needs compositing
parentData: not positioned; offset=Offset(0.0, 0.0) (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, 0.0<=h<=647.7)
size: Size(785.3, 647.7)
child: RenderIgnorePointer#444c8 relayoutBoundary=up6 NEEDS-PAINT
needs compositing
parentData: <none> (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, 0.0<=h<=647.7)
size: Size(785.3, 647.7)
ignoring: false
ignoringSemantics: null
child: RenderStack#1a31a relayoutBoundary=up7 NEEDS-PAINT
needs compositing
parentData: <none> (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, 0.0<=h<=647.7)
size: Size(785.3, 647.7)
alignment: AlignmentDirectional.topStart
textDirection: ltr
fit: loose
child 1: RenderFlex#7b1b6 relayoutBoundary=up8 NEEDS-PAINT
needs compositing
parentData: not positioned; offset=Offset(0.0, 0.0) (can use size)
constraints: BoxConstraints(0.0<=w<=785.3, 0.0<=h<=647.7)
size: Size(785.3, 647.7)
direction: horizontal
mainAxisAlignment: start
mainAxisSize: max
crossAxisAlignment: start
textDirection: ltr
verticalDirection: down
spacing: 0.0
════════════════════════════════════════════════════════════════════════════════
════════ Exception caught by gestures library ══════════════════════════════════
'package:flutter/src/rendering/stack.dart': Failed assertion: line 799 pos 12: 'firstChild == null || child != null': is not true.
════════════════════════════════════════════════════════════════════════════════
════════ Exception caught by gestures library ══════════════════════════════════
'package:flutter/src/rendering/stack.dart': Failed assertion: line 799 pos 12: 'firstChild == null || child != null': is not true.
════════════════════════════════════════════════════════════════════════════════
Expected results
Render with the one remaining child
Actual results
Error thrown as above
Code sample
Code sample
The code for this is too complex in terms of context for me to spend my time trying to extract a reproducible example. Framework threw the error, asked me to report it, I'm reporting it.
Screenshots or Video
Screenshots / Video demonstration
[Upload media here]
Logs
Logs
[Paste your logs here]Flutter Doctor output
NOTE: this is for MacOS/Windows application, so issues with Android tool chain and Chrome are irrelevant. Run platform was Windows.
PS F:\work\FractalOutliner\repo\FractalOutliner\flutter_app\fractal_outliner> flutter doctor -v
[√] Flutter (Channel stable, 3.29.0, on Microsoft Windows [Version 10.0.19045.5608], locale en-US) [281ms]
• Flutter version 3.29.0 on channel stable at F:\dev\flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 35c388a (6 weeks ago), 2025-02-10 12:48:41 -0800
• Engine revision f73bfc4
• Dart version 3.7.0
• DevTools version 2.42.2
[√] Windows Version (10 Home 64-bit, 22H2, 2009) [895ms]
[X] Android toolchain - develop for Android devices [93ms]
X Unable to locate Android SDK.
Install Android Studio from: https://developer.android.com/studio/index.html
On first launch it will assist you in installing the Android SDK components.
(or visit https://flutter.dev/to/windows-android-setup for detailed instructions).
If the Android SDK has been installed to a custom location, please use
flutter config --android-sdk to update to that location.
[X] Chrome - develop for the web (Cannot find Chrome executable at .\Google\Chrome\Application\chrome.exe) [77ms]
! Cannot find Chrome. Try setting CHROME_EXECUTABLE to a Chrome executable.
[√] Visual Studio - develop Windows apps (Visual Studio Community 2022 17.13.0) [76ms]
• Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
• Visual Studio Community 2022 version 17.13.35806.99
• Windows 10 SDK version 10.0.22621.0
[!] Android Studio (not installed) [11ms]
• Android Studio not found; download from https://developer.android.com/studio/index.html
(or visit https://flutter.dev/to/windows-android-setup for detailed instructions).
[√] Connected device (2 available) [54ms]
• Windows (desktop) • windows • windows-x64 • Microsoft Windows [Version 10.0.19045.5608]
• Edge (web) • edge • web-javascript • Microsoft Edge 134.0.3124.72
[√] Network resources [528ms]
• All expected network resources are available.
! Doctor found issues in 3 categories.
PS F:\work\FractalOutliner\repo\FractalOutliner\flutter_app\fractal_outliner>