[web][a11y] Fix the semantics tree reconstruction logic when a subtree is reparented to another node. #177069
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This pull request addresses an issue with semantics tree reconstruction when a subtree is reparented. The fix introduces a new traversal method, _visitDepthFirstInTraversalOrder2, to correctly identify and preserve reparented nodes and their descendants, preventing them from being incorrectly removed. A corresponding regression test has been added to validate this logic.
The approach is solid and the test case is well-designed. However, I've identified a critical compilation error in the new traversal method due to an undefined variable in a recursive call. I've also included a suggestion to improve the method's name for better code clarity. Please see my specific comments for details.
engine/src/flutter/lib/web_ui/lib/src/engine/semantics/semantics.dart
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CI had a failure that stopped further tests from running. We need to investigate to determine the root cause. SHA at time of execution: b7fe905. Possible causes:
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…a subtree is reparented to another node. (flutter/flutter#177069)
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Roll Flutter from a873a27 to 891d7d5 (32 revisions) flutter/flutter@a873a27...891d7d5 2025-10-18 engine-flutter-autoroll@skia.org Roll Skia from b4981b621a54 to 74df18176924 (1 revision) (flutter/flutter#177204) 2025-10-18 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from ZHuhfPyyV-LcKDLRh... to M8WT2GMY46e_0fFho... (flutter/flutter#177200) 2025-10-18 59215665+davidhicks980@users.noreply.github.com [material/dropdown_menu.dart] Refactor _RenderDropdownMenuBody.computeDryLayout (flutter/flutter#176503) 2025-10-18 engine-flutter-autoroll@skia.org Roll Skia from 579c72d673dd to b4981b621a54 (2 revisions) (flutter/flutter#177199) 2025-10-17 engine-flutter-autoroll@skia.org Roll Skia from 89a8bc508a7c to 579c72d673dd (15 revisions) (flutter/flutter#177194) 2025-10-17 paulberry@google.com [test_fixes] Enable `deprecated_member_use_from_same_package`. (flutter/flutter#177183) 2025-10-17 jhy03261997@gmail.com [a11y] fix table semantics cache for cells (flutter/flutter#177073) 2025-10-17 mdebbar@google.com [web] Self-cleaning service worker (flutter/flutter#176834) 2025-10-17 engine-flutter-autoroll@skia.org Manual roll Skia from 2d9df7c70b6f to 89a8bc508a7c (24 revisions) (flutter/flutter#177182) 2025-10-17 matt.kosarek@canonical.com Fixing WindowManagerTest::DialogCanNeverBeFullscreen possibly hanging (flutter/flutter#177179) 2025-10-17 jhy03261997@gmail.com [VPAT][A11y][a11y-app] Add a text label to slider. (flutter/flutter#177130) 2025-10-17 engine-flutter-autoroll@skia.org Manual roll Dart SDK from a4485e5ef821 to a66f334fee2a (5 revisions) (flutter/flutter#177142) 2025-10-17 jhy03261997@gmail.com [web][a11y] Fix the semantics tree reconstruction logic when a subtree is reparented to another node. (flutter/flutter#177069) 2025-10-17 rmolivares@renzo-olivares.dev `SelectableRegion` should use flutter rendered menu on the web for Android and iOS (flutter/flutter#177122) 2025-10-17 kazbek.sultanov.doc@gmail.com Refactor: Convert Title widget to StatefulWidget (flutter/flutter#176010) 2025-10-17 jessiewong401@gmail.com Bump AGP, KGP, Gradle Templates (flutter/flutter#176858) 2025-10-17 engine-flutter-autoroll@skia.org Roll Packages from 835dccb to 3747006 (3 revisions) (flutter/flutter#177170) 2025-10-17 codefu@google.com Mark windows_unopt test as flakey (flutter/flutter#177173) 2025-10-17 rmolivares@renzo-olivares.dev Tapping outside of `SelectableRegion` should dismiss the selection (flutter/flutter#176843) 2025-10-17 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from _dd0Jv50H0oUI2Ad8... to ZHuhfPyyV-LcKDLRh... (flutter/flutter#177137) 2025-10-17 jason-simmons@users.noreply.github.com Manual roll Dart to a4485e5ef821 (3.11.0-25.0.dev) (flutter/flutter#177132) 2025-10-17 ahmedsameha1@gmail.com Make sure that a MenuAcceleratorLabel doesn't crash in 0x0 environment (flutter/flutter#176646) 2025-10-16 ahmedsameha1@gmail.com Make sure that a NavigationRail doesn't crash in 0x0 environment (flutter/flutter#177022) 2025-10-16 ahmedsameha1@gmail.com Make sure that a SubmenuButton doesn't crash in 0x0 environment (flutter/flutter#176535) 2025-10-16 mail@leuchte.net Fix typo in ButtonBar documentation (flutter/flutter#177078) 2025-10-16 ahmedsameha1@gmail.com Make sure that an InkResponse doesn't crash in 0x0 environment (flutter/flutter#175426) 2025-10-16 jessiewong401@gmail.com [Gradle 9] Resolve Gradle 9 Deprecations in flutter/flutter part 1 (flutter/flutter#176865) 2025-10-16 1063596+reidbaker@users.noreply.github.com Revert "Resolve resolve native Flutter dependencies in Android Studio (#167332)" (flutter/flutter#177053) 2025-10-16 engine-flutter-autoroll@skia.org Manual roll Dart SDK from 2d8e0359a767 to 25b6094026e4 (5 revisions) (flutter/flutter#177109) 2025-10-16 maxenceb1207@gmail.com Add textfield prop to SearchAnchor (flutter/flutter#174497) 2025-10-16 p1318k@gmail.com Fix crash when NSAttributedString is passed to insertText on macOS (flutter/flutter#176329) 2025-10-16 jmccandless@google.com Correct basque time format (flutter/flutter#177031) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC stuartmorgan@google.com,tarrinneal@google.com on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md ...
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…e is reparented to another node. (flutter#177069) issue fix: flutter#175180 The bug was like this: 1. a tree like 1--2--3--4 2. remove node 2 and reattach node 3 to 1, the tree is now 1--3--4, it's correct on the framework side. 3. on the web side, the tree reconstruction logic is wrong and the tree become 1---3, the node 4 is removed wrongly. When a node is detached from the tree, but its children node is attached to a new parent, we need to stop searching the subtree and stop removing the reparented subtree! So we need a DFS function that can skip subtree but wont stop the whole searching. ## Pre-launch Checklist - [ ] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [ ] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [ ] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [ ] I signed the [CLA]. - [ ] I listed at least one issue that this PR fixes in the description above. - [ ] I updated/added relevant documentation (doc comments with `///`). - [ ] I added new tests to check the change I am making, or this PR is [test-exempt]. - [ ] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [ ] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed. <!-- Links --> [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md
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issue fix: #175180
The bug was like this:
When a node is detached from the tree, but its children node is attached to a new parent, we need to stop searching the subtree and stop removing the reparented subtree!
So we need a DFS function that can skip subtree but wont stop the whole searching.
Pre-launch Checklist
///).If you need help, consider asking for advice on the #hackers-new channel on Discord.
Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. Comments from the
gemini-code-assistbot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.