[material_ui] Fix ExpansionTile WidgetSpan semantics assertion by ahamsel · Pull Request #12765 · flutter/packages

ahamsel · 2026-09-05T11:58:19Z

On Android, embedding an ExpansionTile in a WidgetSpan can trigger a sibling-configuration conflict assertion when semantics are enabled. Its live-region Semantics uses AccessibilityFocusBlockType.blockNode but can merge into the surrounding semantics tree.

This makes the live region a semantics container, so blockNode applies to an explicit node. The regression test uses the simpler reproduction suggested in flutter/flutter#190639 and relies on the semantics handle managed by testWidgets.

Fixes flutter/flutter#188298.

This ports flutter/flutter#190639 to packages/material_ui. The earlier package PR, #12383, was closed while contributions were paused. On October 2, I rebased this replacement onto current main (10cde9a3b) to refresh its stale CI configuration. The contribution itself is unchanged: the semantics fix, its regression test, and a pending changelog entry. There are no custom CI changes in this PR.

I used AI to help with the fix and regression test.

Pre-Review Checklist

Local validation after the October 2 rebase, on macOS with the already-installed Flutter 3.47.5 / Dart 3.13.4:

Full material_ui suite: flutter test --no-pub --concurrency=2 — 8,222 passed, 12 existing skips, no failures.
Full example suite: flutter test --no-pub --concurrency=1 in packages/material_ui/example — 406 passed, two existing skips, no failures.
ExpansionTile file separately: 64 passed, one existing skip (also included in the full suite).
Defaults generator suite: dart test — 72 passed.
Full-package flutter analyze --no-pub: no issues.
Dart formatting and git diff --check: passed.
dart run script/tool/bin/flutter_plugin_tools.dart validate --packages material_ui --check-for-missing-changes --base-branch upstream/main: passed.

I repeated the regression's fail-without-fix check on the rebased branch: removing container: true produces the original !conflict assertion; restoring it makes the test pass. The existing flutter_goldens harness skips golden-image comparisons; I did not change that behavior. These are local test results, not a claim that repository-wide CI has passed.

GitHub automatically removed the CICD label after the October 2 push. Could a maintainer reapply it for the refreshed head so the repository presubmits can run?

The release metadata uses material_ui's batch-release convention: a pending changelog entry with version: patch.

Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. 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.

Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩²

gemini-code-assist

Code Review

This pull request sets container: true on the Semantics widget in ExpansionTile to ensure the live region forms the node that blockNode removes from focus traversal, resolving an Android semantics assertion when embedded in a WidgetSpan. It also adds a regression test for this scenario and a changelog entry. There are no review comments, so no feedback is provided.

QuncCccccc · 2026-09-08T21:32:33Z

Thanks for the contribution! You haven’t completed all of the items in the PR checklist above, so I’m assuming this is a work in progress and am marking it as a Draft. Please review the checklist, updating the PR as appropriate, and when that’s complete please feel free to mark the PR as ready for review.

ahamsel · 2026-09-08T22:37:34Z

Thanks for flagging this. I've completed the checklist and marked the PR ready for review.

The full material_ui, example, accessibility-app, and defaults-generator suites passed locally: 8,769 tests passed, with 13 existing skips. Full-package analysis, formatting, and repository validation also passed. I've added the results and the existing golden-comparison limitation to the description.

CI is still awaiting the CICD label. Could a maintainer enable it when convenient?

gemini-code-assist

Code Review

This pull request sets container: true on the Semantics widget within ExpansionTile to resolve an Android semantics assertion when embedded in a WidgetSpan, and includes a regression test. The review feedback recommends using addTearDown to ensure the SemanticsHandle is properly disposed of even if the test fails.

gemini-code-assist · 2026-09-08T22:38:13Z

+      final SemanticsHandle handle = tester.ensureSemantics();
+
+      await tester.pumpWidget(
+        const MaterialApp(
+          home: Scaffold(
+            body: Text.rich(
+              TextSpan(
+                children: <InlineSpan>[
+                  WidgetSpan(
+                    child: ExpansionTile(
+                      title: Text('Header'),
+                      children: <Widget>[Text('Details')],
+                    ),
+                  ),
+                ],
+              ),
+            ),
+          ),
+        ),
+      );
+      expect(find.text('Header'), findsOneWidget);
+      handle.dispose();


To ensure that the SemanticsHandle is always disposed of, even if an assertion or expectation fails during the test, it is recommended to use addTearDown(handle.dispose); immediately after creating the handle. This prevents semantics from leaking into subsequent tests in the suite, which can cause unexpected failures or flakiness.

final SemanticsHandle handle = tester.ensureSemantics(); addTearDown(handle.dispose); await tester.pumpWidget( const MaterialApp( home: Scaffold( body: Text.rich( TextSpan( children: <InlineSpan>[ WidgetSpan( child: ExpansionTile( title: Text('Header'), children: <Widget>[Text('Details')], ), ), ], ), ), ), ), ); expect(find.text('Header'), findsOneWidget);

Thanks. I tried addTearDown(handle.dispose), but this test then failed with "A SemanticsHandle was active at the end of the test": Flutter checks for active handles before that teardown runs.

testWidgets already enables semantics by default and manages its own handle, so I removed the redundant manual handle instead. All 64 ExpansionTile tests pass, with one existing skip, and formatting and analysis pass. I also rechecked that the simplified regression still fails with the original !conflict assertion when container: true is removed, then passes when it is restored.

elliette · 2026-10-01T23:39:34Z

Removing myself as reviewer since I will be out for the next couple weeks. This should get picked up in the next triage meeting.

QuncCccccc

LGTM. Thanks for your contribution!

Adding an a11y expert as a second reviewer:)

hannah-hyj

LGTM, thanks!

flutter/packages@54706bd...d8d9e97 2026-10-09 [email protected] [pigeon] Reject unsupported native interop features and fix generated code that doesn't compile (flutter/packages#13153) 2026-10-09 [email protected] [material_ui] Fix ExpansionTile WidgetSpan semantics assertion (flutter/packages#12765) 2026-10-08 [email protected] [in_app_purchase_storekit] Complete StoreKit 2 `finish` when the transaction is not found (flutter/packages#13037) 2026-10-08 [email protected] [video_player] Fix crash when videoTrack has zero-duration minFrameDuration (flutter/packages#12796) 2026-10-08 [email protected] [google_maps_flutter_platform_interface] Add map background color configuration (flutter/packages#13014) If this roll has caused a breakage, revert this CL and set the roller to dry run mode using the controls here: https://autoroll.skia.org/r/flutter-packages-flutter-autoroll Please CC [email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Flutter: 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

github-actions Bot added p: material_ui triage-design Should be looked at in design triage labels Sep 5, 2026

ahamsel mentioned this pull request Sep 5, 2026

[material_ui] Fix ExpansionTile nested WidgetSpan semantics assertion #12383

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ahamsel marked this pull request as ready for review September 5, 2026 12:06

ahamsel mentioned this pull request Sep 5, 2026

Fix ExpansionTile semantics with WidgetSpan titles flutter/flutter#190639

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gemini-code-assist Bot reviewed Sep 5, 2026

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QuncCccccc marked this pull request as draft September 8, 2026 21:32

ahamsel marked this pull request as ready for review September 8, 2026 22:37

gemini-code-assist Bot reviewed Sep 8, 2026

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elliette self-requested a review September 29, 2026 22:16

elliette added the CICD Run CI/CD label Oct 1, 2026

elliette removed their request for review October 1, 2026 23:39

ahamsel force-pushed the fix/material-ui-expansion-tile-widgetspan-semantics branch from 1d2f389 to fffb2b2 Compare October 3, 2026 01:33

flutter-dashboard Bot removed the CICD Run CI/CD label Oct 3, 2026

QuncCccccc self-requested a review October 6, 2026 21:27

QuncCccccc added the CICD Run CI/CD label Oct 6, 2026

QuncCccccc approved these changes Oct 9, 2026

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QuncCccccc requested review from chunhtai and hannah-hyj October 9, 2026 01:30

hannah-hyj approved these changes Oct 9, 2026

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ahamsel added 3 commits October 8, 2026 18:39

[material_ui] Fix ExpansionTile WidgetSpan semantics

1c82319

[material_ui] Simplify ExpansionTile WidgetSpan regression test

d0b700a

[material_ui] Let testWidgets manage regression-test semantics

d5513e1

QuncCccccc force-pushed the fix/material-ui-expansion-tile-widgetspan-semantics branch from fffb2b2 to d5513e1 Compare October 9, 2026 01:39

flutter-dashboard Bot removed the CICD Run CI/CD label Oct 9, 2026

QuncCccccc added CICD Run CI/CD autosubmit Merge PR when tree becomes green via auto submit App labels Oct 9, 2026

auto-submit Bot merged commit 1f55bfa into flutter:main Oct 9, 2026
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engine-flutter-autoroll mentioned this pull request Oct 9, 2026

Roll Packages from 54706bdee543 to d8d9e97d2d02 (5 revisions) flutter/flutter#194080

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[material_ui] Fix ExpansionTile WidgetSpan semantics assertion - #12765

[material_ui] Fix ExpansionTile WidgetSpan semantics assertion#12765
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ahamsel:fix/material-ui-expansion-tile-widgetspan-semantics

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