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Use null-aware elements in cupertino/nav_bar.dart#181237

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brahim-guaali:fix/172188-null-aware-cupertino-nav-bar
Jan 22, 2026
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Use null-aware elements in cupertino/nav_bar.dart#181237
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brahim-guaali:fix/172188-null-aware-cupertino-nav-bar

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@brahim-guaali

@brahim-guaali brahim-guaali commented Jan 21, 2026 •
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Description

Adopts null-aware element syntax (?x) in cupertino/nav_bar.dart, replacing 16 instances of the verbose if (x != null) x! pattern in the _NavigationBarTransition widget's children list.

Fixes #172188

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.
  • I listed at least one issue that this PR fixes in the description above.
  • I added new tests to check the change I am making, or this PR is test-exempt.
  • All existing and new tests are passing.

talabat.com contributions Talabat Flutter PRs

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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.

@github-actions github-actions Bot added framework flutter/packages/flutter repository. See also f: labels. f: cupertino flutter/packages/flutter/cupertino repository labels Jan 21, 2026
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Code Review

This pull request successfully refactors the _NavigationBarTransition widget in cupertino/nav_bar.dart by adopting the more concise null-aware element syntax (?x). This change replaces 16 instances of the verbose if (x != null) x! pattern, significantly improving code readability and conciseness without altering functionality. The update aligns with modern Dart/Flutter best practices for handling nullable types.

@dkwingsmt dkwingsmt self-requested a review January 21, 2026 19:24
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dkwingsmt approved these changes Jan 22, 2026
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LGTM. Thanks for the cleanup!

loic-sharma
loic-sharma approved these changes Jan 22, 2026
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LGTM but this will need a test exemption before we can land this :)

I requested one here: https://discord.com/channels/608014603317936148/608018585025118217/1463705291681038601

@dkwingsmt dkwingsmt added the autosubmit Merge PR when tree becomes green via auto submit App label Jan 22, 2026
@auto-submit auto-submit Bot added this pull request to the merge queue Jan 22, 2026
Merged via the queue into flutter:master with commit 758db16 Jan 22, 2026
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@flutter-dashboard flutter-dashboard Bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Jan 22, 2026
@stuartmorgan-g

stuartmorgan-g commented Jan 22, 2026

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test-exempt: code refactor with no semantic change

@engine-flutter-autoroll engine-flutter-autoroll mentioned this pull request Jan 22, 2026
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engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Jan 22, 2026
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758db16cc Use null-aware elements in cupertino/nav_bar.dart (flutter/…
b95f1b8 
…flutter#181237)
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engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Jan 22, 2026
@engine-flutter-autoroll
758db16cc Use null-aware elements in cupertino/nav_bar.dart (flutter/…
8712069 
…flutter#181237)
@engine-flutter-autoroll engine-flutter-autoroll mentioned this pull request Jan 22, 2026
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engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Jan 22, 2026
@engine-flutter-autoroll
758db16cc Use null-aware elements in cupertino/nav_bar.dart (flutter/…
d6ba410 
…flutter#181237)
@engine-flutter-autoroll engine-flutter-autoroll mentioned this pull request Jan 23, 2026
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…flutter#181237)
auto-submit Bot pushed a commit to flutter/packages that referenced this pull request Jan 23, 2026
@engine-flutter-autoroll
Roll Flutter from 48c2475 to bfc9041eb118 (173 revisions) (#10862)
9e3470c 
Roll Flutter from 48c2475 to bfc9041eb118 (173 revisions)

flutter/flutter@48c2475...bfc9041

2026-01-23 matt.kosarek@canonical.com No longer exiting the application when the RegularWindow is destroyed + resolving the window created promise after runWidget (flutter/flutter#181339)
2026-01-23 kazbek.sultanov.doc@gmail.com Remove unnecessary Material import from dialog_test.dart (flutter/flutter#181249)
2026-01-23 engine-flutter-autoroll@skia.org Roll Skia from 8e516fe6828f to db10db8bd55f (1 revision) (flutter/flutter#181379)
2026-01-23 50643541+Mairramer@users.noreply.github.com Reset TextFormField to initial value after state change (flutter/flutter#181199)
2026-01-23 engine-flutter-autoroll@skia.org Roll Dart SDK from 980b2b41d36e to e82d7ad1855e (1 revision) (flutter/flutter#181375)
2026-01-23 engine-flutter-autoroll@skia.org Roll Skia from 3e86f377d300 to 8e516fe6828f (4 revisions) (flutter/flutter#181370)
2026-01-23 kazbek.sultanov.doc@gmail.com Remove unnecessary Material import from sliver_visibility_test (flutter/flutter#181248)
2026-01-23 43635580+Lilian-C@users.noreply.github.com Add bottom navigation bar item semantics label (flutter/flutter#180577)
2026-01-23 58190796+MitchellGoodwin@users.noreply.github.com Make topGap not required for CupertinoSheetTransition (flutter/flutter#181269)
2026-01-23 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from b4cLyhuxciUC-4zCJ... to n7NohL9DPpEuPjNt9... (flutter/flutter#181365)
2026-01-23 engine-flutter-autoroll@skia.org Roll Dart SDK from 806f04638561 to 980b2b41d36e (1 revision) (flutter/flutter#181364)
2026-01-23 34871572+gmackall@users.noreply.github.com Reland hybrid views test (flutter/flutter#181336)
2026-01-23 git@reb0.org Revert DropdownMenu non-nullable breaking change (flutter/flutter#181074)
2026-01-23 dkwingsmt@users.noreply.github.com Fix leaks in `flutter_test` tests (flutter/flutter#180879)
2026-01-23 97480502+b-luk@users.noreply.github.com Re-enable fragment_shader_tests.dart 'Shader Compiler appropriately pads vec3 uniform arrays' test on Vulkan (flutter/flutter#181292)
2026-01-23 bkonyi@google.com [ Tool ] Fix `update-packages` failing due to mismatched dependencies between flutter_tools and the framework (flutter/flutter#181335)
2026-01-23 jason-simmons@users.noreply.github.com [Impeller] Make dynamically created shader metadata for runtime effects consistent with metadata for built-in shaders (flutter/flutter#181201)
2026-01-23 97480502+b-luk@users.noreply.github.com Broaden the applicability of `Color` fix_data rules from flutter/painting.dart (flutter/flutter#181093)
2026-01-23 15619084+vashworth@users.noreply.github.com Fixes macOS App.framework not being codesigned or find framework (flutter/flutter#181348)
2026-01-22 69134234+sutes-work@users.noreply.github.com Roll Fuchsia GN SDK from NAEC5tfgSl8g94nwp... to JLBh4Z9PKsjIJcqDU... (flutter/flutter#181139)
2026-01-22 engine-flutter-autoroll@skia.org Roll Dart SDK from ab4640ea82e9 to 806f04638561 (2 revisions) (flutter/flutter#181347)
2026-01-22 sokolovskyi.konstantin@gmail.com Add ExpansibleController.toggle method. (flutter/flutter#181320)
2026-01-22 42980667+srivats22@users.noreply.github.com Fixes Typo in codebase (flutter/flutter#181256)
2026-01-22 engine-flutter-autoroll@skia.org Roll Skia from 4766615bcc96 to 3e86f377d300 (3 revisions) (flutter/flutter#181346)
2026-01-22 ahmedsameha1@gmail.com Make sure that a Hero doesn't crash in 0x0 environment (flutter/flutter#180954)
2026-01-22 jason-simmons@users.noreply.github.com Reland "Fix capitalization of the path to FlutterWindowControllerTest.mm in the macOS platform build script" (flutter/flutter#181200)
2026-01-22 engine-flutter-autoroll@skia.org Roll Skia from 6e9746be8c4a to 4766615bcc96 (3 revisions) (flutter/flutter#181331)
2026-01-22 kazbek.sultanov.doc@gmail.com Fix remove material import textfield (flutter/flutter#181254)
2026-01-22 15619084+vashworth@users.noreply.github.com Add FlutterFramework as an Xcode SwiftPM local package override (flutter/flutter#179512)
2026-01-22 engine-flutter-autoroll@skia.org Roll Dart SDK from 7bd4c68b625c to ab4640ea82e9 (1 revision) (flutter/flutter#181324)
2026-01-22 engine-flutter-autoroll@skia.org Roll Packages from d80c60e to 9010299 (9 revisions) (flutter/flutter#181323)
2026-01-22 engine-flutter-autoroll@skia.org Roll Dart SDK from 2d53a77adc5d to 7bd4c68b625c (2 revisions) (flutter/flutter#181316)
2026-01-22 engine-flutter-autoroll@skia.org Roll Skia from 3f6949bc5780 to 6e9746be8c4a (2 revisions) (flutter/flutter#181311)
2026-01-22 engine-flutter-autoroll@skia.org Roll Skia from ef6efc358b4a to 3f6949bc5780 (2 revisions) (flutter/flutter#181307)
2026-01-22 engine-flutter-autoroll@skia.org Roll Dart SDK from 5d7c8faf2e41 to 2d53a77adc5d (1 revision) (flutter/flutter#181305)
2026-01-22 120639059+Enderjua@users.noreply.github.com [Material] update hourFormat to use Dart 3 switch expression (flutter/flutter#181041)
2026-01-22 146823759+brahim-guaali@users.noreply.github.com Use null-aware elements in cupertino/nav_bar.dart (flutter/flutter#181237)
2026-01-22 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from b2KIEXVAlEqImQ9VO... to b4cLyhuxciUC-4zCJ... (flutter/flutter#181297)
2026-01-22 137456488+flutter-pub-roller-bot@users.noreply.github.com Roll pub packages (flutter/flutter#181295)
2026-01-22 30870216+gaaclarke@users.noreply.github.com Enables fragment shader test for impeller (fixes mat2 on vulkan) (flutter/flutter#181013)
2026-01-21 engine-flutter-autoroll@skia.org Roll Dart SDK from 366200db1aa1 to 5d7c8faf2e41 (4 revisions) (flutter/flutter#181290)
2026-01-21 engine-flutter-autoroll@skia.org Roll Skia from b5ec89e31f59 to ef6efc358b4a (19 revisions) (flutter/flutter#181289)
2026-01-21 brackenavaron@gmail.com fix description for semantics finders (flutter/flutter#181214)
2026-01-21 ahmedsameha1@gmail.com Make sure that an Icon doesn't crash in 0x0 environment (flutter/flutter#181021)
2026-01-21 ahmedsameha1@gmail.com Make sure that a GridPaper doesn't crash in 0x0 environment (flutter/flutter#180906)
2026-01-21 magder@google.com Bring Linux coverage out of bringup (flutter/flutter#181280)
...
flutter-zl pushed a commit to flutter-zl/flutter that referenced this pull request Feb 10, 2026
@brahim-guaali @flutter-zl
Use null-aware elements in cupertino/nav_bar.dart (flutter#181237)
b6beb6a 
## Description

Adopts null-aware element syntax (`?x`) in `cupertino/nav_bar.dart`,
replacing 16 instances of the verbose `if (x != null) x!` pattern in the
`_NavigationBarTransition` widget's children list.

Fixes flutter#172188

## 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].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] All existing and new tests are passing.

[Contributor Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md

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creatorpiyush pushed a commit to creatorpiyush/packages that referenced this pull request Jun 10, 2026
@engine-flutter-autoroll
Roll Flutter from 48c2475 to bfc9041eb118 (173 revisions) (flutter#10862
93314f2 
)

Roll Flutter from 48c2475 to bfc9041eb118 (173 revisions)

flutter/flutter@48c2475...bfc9041

2026-01-23 matt.kosarek@canonical.com No longer exiting the application when the RegularWindow is destroyed + resolving the window created promise after runWidget (flutter/flutter#181339)
2026-01-23 kazbek.sultanov.doc@gmail.com Remove unnecessary Material import from dialog_test.dart (flutter/flutter#181249)
2026-01-23 engine-flutter-autoroll@skia.org Roll Skia from 8e516fe6828f to db10db8bd55f (1 revision) (flutter/flutter#181379)
2026-01-23 50643541+Mairramer@users.noreply.github.com Reset TextFormField to initial value after state change (flutter/flutter#181199)
2026-01-23 engine-flutter-autoroll@skia.org Roll Dart SDK from 980b2b41d36e to e82d7ad1855e (1 revision) (flutter/flutter#181375)
2026-01-23 engine-flutter-autoroll@skia.org Roll Skia from 3e86f377d300 to 8e516fe6828f (4 revisions) (flutter/flutter#181370)
2026-01-23 kazbek.sultanov.doc@gmail.com Remove unnecessary Material import from sliver_visibility_test (flutter/flutter#181248)
2026-01-23 43635580+Lilian-C@users.noreply.github.com Add bottom navigation bar item semantics label (flutter/flutter#180577)
2026-01-23 58190796+MitchellGoodwin@users.noreply.github.com Make topGap not required for CupertinoSheetTransition (flutter/flutter#181269)
2026-01-23 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from b4cLyhuxciUC-4zCJ... to n7NohL9DPpEuPjNt9... (flutter/flutter#181365)
2026-01-23 engine-flutter-autoroll@skia.org Roll Dart SDK from 806f04638561 to 980b2b41d36e (1 revision) (flutter/flutter#181364)
2026-01-23 34871572+gmackall@users.noreply.github.com Reland hybrid views test (flutter/flutter#181336)
2026-01-23 git@reb0.org Revert DropdownMenu non-nullable breaking change (flutter/flutter#181074)
2026-01-23 dkwingsmt@users.noreply.github.com Fix leaks in `flutter_test` tests (flutter/flutter#180879)
2026-01-23 97480502+b-luk@users.noreply.github.com Re-enable fragment_shader_tests.dart 'Shader Compiler appropriately pads vec3 uniform arrays' test on Vulkan (flutter/flutter#181292)
2026-01-23 bkonyi@google.com [ Tool ] Fix `update-packages` failing due to mismatched dependencies between flutter_tools and the framework (flutter/flutter#181335)
2026-01-23 jason-simmons@users.noreply.github.com [Impeller] Make dynamically created shader metadata for runtime effects consistent with metadata for built-in shaders (flutter/flutter#181201)
2026-01-23 97480502+b-luk@users.noreply.github.com Broaden the applicability of `Color` fix_data rules from flutter/painting.dart (flutter/flutter#181093)
2026-01-23 15619084+vashworth@users.noreply.github.com Fixes macOS App.framework not being codesigned or find framework (flutter/flutter#181348)
2026-01-22 69134234+sutes-work@users.noreply.github.com Roll Fuchsia GN SDK from NAEC5tfgSl8g94nwp... to JLBh4Z9PKsjIJcqDU... (flutter/flutter#181139)
2026-01-22 engine-flutter-autoroll@skia.org Roll Dart SDK from ab4640ea82e9 to 806f04638561 (2 revisions) (flutter/flutter#181347)
2026-01-22 sokolovskyi.konstantin@gmail.com Add ExpansibleController.toggle method. (flutter/flutter#181320)
2026-01-22 42980667+srivats22@users.noreply.github.com Fixes Typo in codebase (flutter/flutter#181256)
2026-01-22 engine-flutter-autoroll@skia.org Roll Skia from 4766615bcc96 to 3e86f377d300 (3 revisions) (flutter/flutter#181346)
2026-01-22 ahmedsameha1@gmail.com Make sure that a Hero doesn't crash in 0x0 environment (flutter/flutter#180954)
2026-01-22 jason-simmons@users.noreply.github.com Reland "Fix capitalization of the path to FlutterWindowControllerTest.mm in the macOS platform build script" (flutter/flutter#181200)
2026-01-22 engine-flutter-autoroll@skia.org Roll Skia from 6e9746be8c4a to 4766615bcc96 (3 revisions) (flutter/flutter#181331)
2026-01-22 kazbek.sultanov.doc@gmail.com Fix remove material import textfield (flutter/flutter#181254)
2026-01-22 15619084+vashworth@users.noreply.github.com Add FlutterFramework as an Xcode SwiftPM local package override (flutter/flutter#179512)
2026-01-22 engine-flutter-autoroll@skia.org Roll Dart SDK from 7bd4c68b625c to ab4640ea82e9 (1 revision) (flutter/flutter#181324)
2026-01-22 engine-flutter-autoroll@skia.org Roll Packages from d80c60e to 9010299 (9 revisions) (flutter/flutter#181323)
2026-01-22 engine-flutter-autoroll@skia.org Roll Dart SDK from 2d53a77adc5d to 7bd4c68b625c (2 revisions) (flutter/flutter#181316)
2026-01-22 engine-flutter-autoroll@skia.org Roll Skia from 3f6949bc5780 to 6e9746be8c4a (2 revisions) (flutter/flutter#181311)
2026-01-22 engine-flutter-autoroll@skia.org Roll Skia from ef6efc358b4a to 3f6949bc5780 (2 revisions) (flutter/flutter#181307)
2026-01-22 engine-flutter-autoroll@skia.org Roll Dart SDK from 5d7c8faf2e41 to 2d53a77adc5d (1 revision) (flutter/flutter#181305)
2026-01-22 120639059+Enderjua@users.noreply.github.com [Material] update hourFormat to use Dart 3 switch expression (flutter/flutter#181041)
2026-01-22 146823759+brahim-guaali@users.noreply.github.com Use null-aware elements in cupertino/nav_bar.dart (flutter/flutter#181237)
2026-01-22 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from b2KIEXVAlEqImQ9VO... to b4cLyhuxciUC-4zCJ... (flutter/flutter#181297)
2026-01-22 137456488+flutter-pub-roller-bot@users.noreply.github.com Roll pub packages (flutter/flutter#181295)
2026-01-22 30870216+gaaclarke@users.noreply.github.com Enables fragment shader test for impeller (fixes mat2 on vulkan) (flutter/flutter#181013)
2026-01-21 engine-flutter-autoroll@skia.org Roll Dart SDK from 366200db1aa1 to 5d7c8faf2e41 (4 revisions) (flutter/flutter#181290)
2026-01-21 engine-flutter-autoroll@skia.org Roll Skia from b5ec89e31f59 to ef6efc358b4a (19 revisions) (flutter/flutter#181289)
2026-01-21 brackenavaron@gmail.com fix description for semantics finders (flutter/flutter#181214)
2026-01-21 ahmedsameha1@gmail.com Make sure that an Icon doesn't crash in 0x0 environment (flutter/flutter#181021)
2026-01-21 ahmedsameha1@gmail.com Make sure that a GridPaper doesn't crash in 0x0 environment (flutter/flutter#180906)
2026-01-21 magder@google.com Bring Linux coverage out of bringup (flutter/flutter#181280)
...
@stuartmorgan-g stuartmorgan-g mentioned this pull request Jun 14, 2026
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@loic-sharma loic-sharma loic-sharma approved these changes
@dkwingsmt dkwingsmt dkwingsmt approved these changes
@gaaclarke gaaclarke gaaclarke approved these changes
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Adopt null aware elements in the framework

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