Migrate to list and builder Sliver convenience constructors #173011

loic-sharma · 2025-07-30T23:45:55Z

In 2022, we introduced new convenience constructors like SliverList.builder and SliverList.list. Unfortunately, LLMs like Gemini seem to prefer the delegate pattern even when these convenience constructors are usable. This updates Flutter's docs, code, and tests to use these convenience constructors where possible. Hopefully this will nudge LLMs to consider using the new APIs :)

I migrated 80% of the code by hand, and 20% using Gemini CLI. See go/loic-ai-log (Google internal) for details.

There's a few locations that I wasn't able to migrate to the convenience constructors due to missing APIs. I filed the following issues:

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. 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.

gemini-code-assist · 2025-07-30T23:45:59Z

Warning

You have reached your daily quota limit. Please wait up to 24 hours and I will start processing your requests again!

loic-sharma · 2025-07-30T23:54:37Z

packages/flutter/lib/src/widgets/automatic_keep_alive.dart

 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

+/// @docImport 'scroll_delegate.dart';


This makes the doc references to SliverChildBuilderDelegate work below.

loic-sharma · 2025-07-31T00:00:48Z

packages/flutter/test/rendering/viewport_test.dart

+                itemCount: 10,
+                itemBuilder: (BuildContext context, int index) {
+                  return SizedBox(height: itemHeight, child: Text('Item ${-index - 1}'));
+                },


I should've used SliverList.list here to exactly match the previous behavior. However, whether these widgets are built lazily or eagerly does not appear to affect the test, and, using SliverList.builder reduces boilerplate. Let me know if you'd like me to switch to SliverList.list though!

loic-sharma · 2025-07-31T00:03:07Z

packages/flutter/test/widgets/scrollable_restoration_test.dart

-                  (int index) => SizedBox(height: 50, child: Text('Tile $index')),
-                ),
-              ),
+            SliverList.builder(


I also switched to SliverList.builder here, let me know if you'd prefer I use SliverList.list here instead.

loic-sharma · 2025-07-31T00:03:53Z

packages/flutter/test/widgets/sliver_appbar_opacity_test.dart

-                return SizedBox(height: 100.0, child: Text('Tile $i'));
-              }),
-            ),
+          SliverList.builder(


Here as well

loic-sharma · 2025-07-31T00:04:52Z

packages/flutter/test/widgets/sliver_list_test.dart

-                    return Chip(key: Key(item), label: Text('Tile $item'));
-                  }).toList(),
-                ),
+              SliverList.builder(


Here as well

loic-sharma · 2025-07-31T00:09:19Z

packages/flutter/test/material/flexible_space_bar_test.dart

-                  for (int i = 0; i < 50; i++)
-                    SizedBox(height: 200, child: Center(child: Text('Item $i'))),
-                ]),
+              SliverList.builder(


Here as well

loic-sharma · 2025-07-31T00:15:29Z

packages/flutter/test/material/scaffold_test.dart

-                      (int index) => SizedBox(height: 100.0, child: Text('B$index')),
-                    ),
-                  ),
+                sliver: SliverList.builder(


Here as well

Piinks

Me the other day, "The constructors were added not too long ago..."
PR description: "In 2022, we introduced..."
🙃 🫠 What is time.

This is awesome, thank you. The places where you refactored for clarity and conciseness LGTM. However, for those under examples/api, there is a description that might contradict the updated snippets. The description immediately follows the {@tool dartpad}, can you check that they still make sense with the updated samples? I think most should be ok.

loic-sharma · 2025-08-02T01:09:06Z

there is a description that might contradict the updated snippets

I did a pass to check that descriptions of all {@tool dartpad} that link an example touched by this PR - they all looked good!

Piinks

I did a pass to check that descriptions of all {@tool dartpad} that link an example touched by this PR - they all looked good!

Thank you! 🙏
LGTM!

loic-sharma · 2025-08-04T22:31:20Z

FYI, I also checked the flutter/website repo this morning - that doesn't have any unnecessary references to sliver delegates, so no need to send a PR for that repo.

…flutter/flutter#173011)

…173011) In 2022, we introduced new convenience constructors like `SliverList.builder` and `SliverList.list`. Unfortunately, LLMs like Gemini seem to prefer the delegate pattern even when these convenience constructors are usable. This updates Flutter's docs, code, and tests to use these convenience constructors where possible. Hopefully this will nudge LLMs to consider using the new APIs :) I migrated 80% of the code by hand, and 20% using Gemini CLI. See [go/loic-ai-log](http://goto.google.com/loic-ai-log) (Google internal) for details. There's a few locations that I wasn't able to migrate to the convenience constructors due to missing APIs. I filed the following issues: 1. flutter#173018 2. flutter#173019 ## 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]. - [ ] I listed at least one issue that this PR fixes in the description above. - [x] 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. - [ ] 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

…flutter/flutter#173011)

…173011) In 2022, we introduced new convenience constructors like `SliverList.builder` and `SliverList.list`. Unfortunately, LLMs like Gemini seem to prefer the delegate pattern even when these convenience constructors are usable. This updates Flutter's docs, code, and tests to use these convenience constructors where possible. Hopefully this will nudge LLMs to consider using the new APIs :) I migrated 80% of the code by hand, and 20% using Gemini CLI. See [go/loic-ai-log](http://goto.google.com/loic-ai-log) (Google internal) for details. There's a few locations that I wasn't able to migrate to the convenience constructors due to missing APIs. I filed the following issues: 1. flutter#173018 2. flutter#173019 ## 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]. - [ ] I listed at least one issue that this PR fixes in the description above. - [x] 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. - [ ] 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

loic-sharma commented Jul 30, 2025

View reviewed changes

loic-sharma commented Jul 31, 2025

View reviewed changes

loic-sharma changed the title ~~Migrate to Sliver list and builder convenience constructors~~ Migrate to list and builder Sliver convenience constructors Jul 31, 2025

loic-sharma force-pushed the sliverlist_delegate_cleanup branch from 1040397 to 372c593 Compare July 31, 2025 18:52

loic-sharma requested a review from Piinks August 1, 2025 03:55

Piinks reviewed Aug 1, 2025

View reviewed changes

loic-sharma added 5 commits August 1, 2025 18:09

Migrate to sliver list and builder convenience constructors

7de1735

Undo changes

8bca1e1

Fix

992315a

Update doc comment

af75b6d

Do a pass on the snippets' intro description

5c9093d

loic-sharma force-pushed the sliverlist_delegate_cleanup branch from 3ffdf30 to 5c9093d Compare August 2, 2025 01:09

Piinks approved these changes Aug 4, 2025

View reviewed changes

loic-sharma added the autosubmit Merge PR when tree becomes green via auto submit App label Aug 4, 2025

auto-submit bot added this pull request to the merge queue Aug 4, 2025

Merged via the queue into flutter:master with commit 384331e Aug 4, 2025
148 of 149 checks passed

flutter-dashboard bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Aug 4, 2025

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 5, 2025

384331e17 Migrate to list and builder Sliver convenience constructors (…

f019bfb

…flutter/flutter#173011)

engine-flutter-autoroll mentioned this pull request Aug 5, 2025

Roll Flutter from beda687d63f2 to b88feac56e98 (18 revisions) flutter/packages#9751

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 5, 2025

384331e17 Migrate to list and builder Sliver convenience constructors (…

47aa85f

…flutter/flutter#173011)

engine-flutter-autoroll mentioned this pull request Aug 5, 2025

Roll Flutter from beda687d63f2 to b88feac56e98 (18 revisions) flutter/packages#9752

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 5, 2025

384331e17 Migrate to list and builder Sliver convenience constructors (…

c483314

…flutter/flutter#173011)

engine-flutter-autoroll mentioned this pull request Aug 5, 2025

Roll Flutter from beda687d63f2 to f6a268392eb6 (19 revisions) flutter/packages#9753

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 5, 2025

384331e17 Migrate to list and builder Sliver convenience constructors (…

4777d9f

…flutter/flutter#173011)

engine-flutter-autoroll mentioned this pull request Aug 5, 2025

Roll Flutter from beda687d63f2 to 41ab71c76b39 (20 revisions) flutter/packages#9754

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 5, 2025

384331e17 Migrate to list and builder Sliver convenience constructors (…

68a79b0

…flutter/flutter#173011)

engine-flutter-autoroll mentioned this pull request Aug 5, 2025

Roll Flutter from beda687d63f2 to 10c32b56f6e5 (21 revisions) flutter/packages#9755

Closed

Piinks mentioned this pull request Aug 8, 2025

Flutter Notable Commits - 2025 #161460

Open

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Nov 12, 2025

384331e17 Migrate to list and builder Sliver convenience constructors (…

0dfc557

…flutter/flutter#173011)

Migrate to list and builder Sliver convenience constructors #173011

Migrate to list and builder Sliver convenience constructors #173011

Uh oh!

Conversation

loic-sharma commented Jul 30, 2025 • edited by parlough Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Pre-launch Checklist

Uh oh!

gemini-code-assist bot commented Jul 30, 2025

Uh oh!

loic-sharma Jul 30, 2025

Choose a reason for hiding this comment

Uh oh!

loic-sharma Jul 31, 2025

Choose a reason for hiding this comment

Uh oh!

loic-sharma Jul 31, 2025

Choose a reason for hiding this comment

Uh oh!

loic-sharma Jul 31, 2025

Choose a reason for hiding this comment

Uh oh!

loic-sharma Jul 31, 2025

Choose a reason for hiding this comment

Uh oh!

loic-sharma Jul 31, 2025

Choose a reason for hiding this comment

Uh oh!

loic-sharma Jul 31, 2025

Choose a reason for hiding this comment

Uh oh!

Piinks left a comment

Choose a reason for hiding this comment

Uh oh!

loic-sharma commented Aug 2, 2025

Uh oh!

Piinks left a comment

Choose a reason for hiding this comment

Uh oh!

loic-sharma commented Aug 4, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

loic-sharma commented Jul 30, 2025 •

edited by parlough

Loading

loic-sharma commented Aug 4, 2025 •

edited

Loading