Migrate to list and builder Sliver convenience constructors by loic-sharma · Pull Request #173011 · flutter/flutter

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.

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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.

…lutter/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

…lutter/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

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loic-sharma commented Jul 31, 2025

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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

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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

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

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Merged via the queue into flutter:master with commit 384331e Aug 4, 2025
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loic-sharma commented Jul 30, 2025 •

edited by parlough

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