Improve Stack widget error message for bounded constraints #173352

Rushikeshbhavsar20 · 2025-08-06T16:26:32Z

📝 Description
This PR improves the assertion error message in the Stack widget when it receives unbounded constraints from its parent (e.g., when placed directly inside a Column or ListView without a bounding widget).

✅ What Changed
Replaced a generic assertion:

With a detailed, developer-friendly message:

Fixes: #172481

This PR addresses the confusing assertion error when a Stack is given unbounded constraints. By adding a descriptive message, developers will have clearer guidance on how to resolve layout issues involving Stack inside widgets like Column or ListView.

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.

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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.

flutter-dashboard · 2025-08-06T16:26:35Z

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

gemini-code-assist

Code Review

This pull request significantly improves the error message for a Stack with unbounded constraints, making it much easier for developers to debug layout issues. This aligns well with the style guide's emphasis on useful error messages. My feedback includes a small refinement to the error message to provide even more specific guidance on when to use certain suggested widgets, further enhancing its helpfulness.

packages/flutter/lib/src/rendering/stack.dart

flutter-dashboard · 2025-08-06T19:42:15Z

Golden file changes have been found for this pull request. Click here to view and triage (e.g. because this is an intentional change).

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Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

Changes reported for pull request #173352 at sha a0e61ab

justinmc

LGTM with a nit. Thanks for improving the error message!

packages/flutter/lib/src/rendering/stack.dart

Add 'constraints' for accuracy in Stack error message

victorsanni

LGTM

…lutter/flutter#173352)

…9862) Manual roll Flutter from e65380a22076 to 960d1078f876 (36 revisions) Manual roll requested by [email protected] flutter/flutter@e65380a...960d107 2025-08-20 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Reapply "Add set semantics enabled API and wire iOS a11y bridge (#161… (#171198)" (flutter/flutter#174153) 2025-08-20 [email protected] Make sure that a Badge doesn't crash in 0x0 environment (flutter/flutter#172065) 2025-08-20 [email protected] Make sure that CalendarDatePicker & YearPicker don't crash in 0x0 environment (flutter/flutter#173408) 2025-08-20 [email protected] Roll Packages from 953cae0 to 58c02e0 (2 revisions) (flutter/flutter#174142) 2025-08-20 [email protected] Make sure that a CircleAvatar doesn't crash in 0x0 environment (flutter/flutter#173498) 2025-08-20 [email protected] Roll Dart SDK from 0d674ff61e2e to 0d0a0c394381 (1 revision) (flutter/flutter#174126) 2025-08-20 [email protected] [Android] Fix version code override calculation in FlutterPlugin (flutter/flutter#174081) 2025-08-20 [email protected] Make sure that a BackButton doesn't crash in 0x0 environment (flutter/flutter#172817) 2025-08-20 [email protected] Roll Dart SDK from c5f5a32df36c to 0d674ff61e2e (1 revision) (flutter/flutter#174099) 2025-08-20 [email protected] feat: Added FocusNode prop for DropdownMenu Trailing Icon Button (flutter/flutter#172753) 2025-08-20 [email protected] Make component theme data defaults use `WidgetStateProperty` (flutter/flutter#173893) 2025-08-20 [email protected] Fix Menu anchor reduce padding on web and desktop (flutter/flutter#172691) 2025-08-20 [email protected] Roll Skia from 4b788d0e5e63 to 721e68fe652a (2 revisions) (flutter/flutter#174095) 2025-08-20 [email protected] Fix time picker period selector a11y touch targets (flutter/flutter#170060) 2025-08-20 [email protected] Fix SegmentedButton focus issue (flutter/flutter#173953) 2025-08-20 [email protected] Roll Dart SDK from e936404543f1 to c5f5a32df36c (1 revision) (flutter/flutter#174089) 2025-08-20 [email protected] Roll Skia from 953bfc0e2f2a to 4b788d0e5e63 (1 revision) (flutter/flutter#174086) 2025-08-19 [email protected] Roll Skia from 07d71ea4d056 to 953bfc0e2f2a (18 revisions) (flutter/flutter#174072) 2025-08-19 [email protected] Roll Dart SDK from 9105d946af95 to e936404543f1 (5 revisions) (flutter/flutter#174074) 2025-08-19 [email protected] NavigationRail correct traversal order (flutter/flutter#173891) 2025-08-19 [email protected] Update CupertinoSliverNavigationBar.middle (flutter/flutter#173868) 2025-08-19 [email protected] Update the AccessibilityPlugin::Announce method to account for the view (flutter/flutter#172669) 2025-08-19 [email protected] [ Widget Preview ] Report an error if a web device is unavailable (flutter/flutter#174036) 2025-08-19 [email protected] [web] Fix error in ClickDebouncer when using VoiceOver (flutter/flutter#174046) 2025-08-19 [email protected] [ Tool ] Add logging to test_adapter_test.dart (flutter/flutter#174073) 2025-08-19 [email protected] Roll Fuchsia Linux SDK from n0EnLlotF2wczlOq_... to V1A1J6uXZ62Q10i9u... (flutter/flutter#174059) 2025-08-19 [email protected] Cleanup legacy `bringup: true` tasks, either removing or enabling (flutter/flutter#173815) 2025-08-19 [email protected] Add Shift+Enter shortcut example for TextField. (flutter/flutter#167952) 2025-08-19 [email protected] Check that the windows architecture is 64-bit and not the process architecture (flutter/flutter#174019) 2025-08-19 [email protected] Improve Stack widget error message for bounded constraints (flutter/flutter#173352) 2025-08-19 [email protected] [VPAT][A11y] AutoComplete dropdown option is missing button role (flutter/flutter#173297) 2025-08-19 [email protected] fix: Android build fails when minSdk is set below 24 in build.gradle.kts (#173823) (flutter/flutter#173825) 2025-08-19 [email protected] Reapply "Add set semantics enabled API and wire iOS a11y bridge (#161… (flutter/flutter#171198) 2025-08-19 [email protected] fix: only use library props for libraries (flutter/flutter#172704) 2025-08-19 [email protected] Roll Packages from 5c52c55 to 953cae0 (22 revisions) (flutter/flutter#174040) 2025-08-19 [email protected] Add `open_jdk` to `Linux linux_android_emulator.debug_x64` (flutter/flutter#173989) 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 [email protected],[email protected] 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 ...

…73352)  📝 Description This PR improves the assertion error message in the Stack widget when it receives unbounded constraints from its parent (e.g., when placed directly inside a Column or ListView without a bounding widget). ✅ What Changed Replaced a generic assertion: <img width="1918" height="300" alt="Screenshot 2025-08-06 213549" src="https://github.com/user-attachments/assets/24d90dfb-6876-4fa2-85ee-01c3c1efd7b8" /> With a detailed, developer-friendly message: <img width="2388" height="630" alt="Screenshot 2025-08-07 011126" src="https://github.com/user-attachments/assets/d74bcd2a-5550-454c-9388-fa9aff9d9167" /> Fixes: flutter#172481 This PR addresses the confusing assertion error when a Stack is given unbounded constraints. By adding a descriptive message, developers will have clearer guidance on how to resolve layout issues involving Stack inside widgets like Column or ListView. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [ ] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] 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.  [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

…lutter/flutter#173352)

…73352)  📝 Description This PR improves the assertion error message in the Stack widget when it receives unbounded constraints from its parent (e.g., when placed directly inside a Column or ListView without a bounding widget). ✅ What Changed Replaced a generic assertion: <img width="1918" height="300" alt="Screenshot 2025-08-06 213549" src="https://github.com/user-attachments/assets/24d90dfb-6876-4fa2-85ee-01c3c1efd7b8" /> With a detailed, developer-friendly message: <img width="2388" height="630" alt="Screenshot 2025-08-07 011126" src="https://github.com/user-attachments/assets/d74bcd2a-5550-454c-9388-fa9aff9d9167" /> Fixes: flutter#172481 This PR addresses the confusing assertion error when a Stack is given unbounded constraints. By adding a descriptive message, developers will have clearer guidance on how to resolve layout issues involving Stack inside widgets like Column or ListView. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [ ] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] 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.  [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

Improve Stack widget error message for bounded constraints

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Rushikeshbhavsar20 and others added 3 commits August 6, 2025 22:42

Merge branch 'master' into improve-stack-error-message

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Clarify when to use Expanded in Stack assertion message

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Merge branch 'master' into improve-stack-error-message

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Merge branch 'master' into improve-stack-error-message

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Merge branch 'master' into improve-stack-error-message

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Rushikeshbhavsar20 added 3 commits August 14, 2025 00:28

Update stack.dart

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Add 'constraints' for accuracy in Stack error message

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Merge branch 'master' into improve-stack-error-message

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