index-out-of-bounds errors causes dart2wasm-compiled app to crash / display broken widgets

[elliette]

I noticed that if I explicitly trigger a RangeError when we setup our analytics (in _analytics_web.dart), it crashes our dart2wasm-compiled app, but not our dart2js app.

Need to investigate more, might be related to this comment here:

devtools/packages/devtools_app/lib/src/shared/framework/app_error_handling.dart

Lines 60 to 66 in 77e37d7

	(Object error, StackTrace stack) {
	// TODO(https://github.com/flutter/devtools/issues/7856): can we detect
	// severe errors here that are related to dart2wasm? Otherwise we may
	// crash DevTools for the user without any way for them to force reload
	// with JS.
	reportError(error, stack: stack, errorType: 'zoneGuarded');
	throw error;

[elliette]

Thank you @kevmoo for clarifying the behavior here.

dart2js (02 optimization level)

Adds checks to compiled code, therefore accessing an invalid index will throw, just like in Dart.

dart2js (04 optimization level) <-- this is what DevTools uses for dart2js

Doesn't add checks, therefore uses default JS behavior. JS returns undefined when accessing an invalid index.

dart2wasm

Throws when accessing an invalid index, just like in Dart.

[elliette]

I looked at the exceptions for our dart2wasm builds to see what our top invalid index errors are.

51 errors (likely fixed)

Note: might be fixed since we haven't seen this since DevTools version 2.45.1

IndexError
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 130:15 | _throwIndexError
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 24:7 | checkIndexBCE
org-dartlang-sdk:///lib/_engine/engine/scene_builder.dart 472:53 | pop
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/rendering/layer.dart 1510:13 | addToScene
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/rendering/layer.dart 711:5 | _addToSceneWithRetainedRendering
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/rendering/layer.dart 1675:5 | addToScene
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/rendering/layer.dart 711:5 | _addToSceneWithRetainedRendering

11 errors

RangeError ([]): Index out of range: index should be less than 71: 78
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 131:3 | _throwIndexError
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 24:7 | checkIndexBCE
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/shared/charts/chart.dart 350:21 | paint
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/rendering/custom_paint.dart 593:13 | _paintWithPainter
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/rendering/custom_paint.dart 641:7 | paint
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/rendering/proxy_box.dart 886:33 | isRepaintBoundary
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/rendering/object.dart 3425:27 | _paintWithContext

9 errors

RangeError ([]): Index out of range: index should be less than 16383: 17339
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 131:3 | _throwIndexError
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 24:7 | checkIndexBCE
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_model.dart 1374:9 | _extension#0|generateStackFramesJson
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_model.dart 1382:5 | _extension#0|generateStackFramesJson
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_model.dart 550:33 | generateFromCpuSamples
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_service.dart 64:42 | CpuProfilerExtension|getCpuProfile
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm

8 errors (fixed, see #9526)

RangeError ([]): Index out of range: index should be less than 8151: 9047
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 131:3 | _throwIndexError
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 24:7 | checkIndexBCE
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_model.dart 1383:7 | _processNode
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_model.dart 1359:5 | generate
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_model.dart 1352:38 | generate
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_model.dart 563:33 | generateFromCpuSamples
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/profiler/cpu_profile_service.dart 65:20 | CpuProfilerExte

6 errors

RangeError ([]): Index out of range: index should be less than 6: 6
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 131:3 | _throwIndexError
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 24:7 | checkIndexBCE
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/widgets/selectable_region.dart 2513:5 | didChangeSelectables
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/widgets/selectable_region.dart 2442:5 | _updateSelectables
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/list.dart 613:13 | length
org-dartlang-sdk:///dart-sdk/lib/collection/list.dart 307:10 | clear

3 errors

RangeError ([]): Index out of range: index should be less than 2: 2
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 131:3 | _throwIndexError
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/error_utils.dart 24:7 | checkIndexBCE
file:///b/s/w/ir/x/w/rc/flutter/packages/flutter/lib/src/widgets/framework.dart 1199:30 | setState
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/inspector/layout_explorer/flex/flex.dart 110:5 | updateHighlighted
file:///b/s/w/ir/x/w/devtools/packages/devtools_app/lib/src/screens/inspector/layout_explorer/ui/layout_explorer_widget.dart 223:5 | _setProperties
org-dartlang-sdk:///dart-sdk/lib/_internal/wasm/lib/async_patch.dart 105:32 | _awaitHelper