feat(assets): add platform-specific asset filtering in pubspec.yaml #176393

hm21 · 2025-10-02T08:01:38Z

Description

This PR introduces platform-specific asset support in pubspec.yaml.

Currently, Flutter does not allow specifying which platforms an asset should be included for.
This results in all declared assets being bundled for every target platform, even if some are irrelevant (e.g. desktop-only or mobile-only images).

What this PR changes

Adds a new optional platforms field under each asset in pubspec.yaml.
The field accepts a list of strings (platform identifiers, e.g. ["android", "ios", "web", "windows", "macos", "linux"]).
Assets with a platforms restriction are only included in the bundle when building for a matching platform.
Invalid values (non-strings or unknown platform names) log an error.

Example

flutter:
  assets:
    - path: assets/logo.png
   
    - path: assets/web_worker.js
      platforms: [web]

    - path: assets/desktop_icon.png
      platforms: [windows, linux, macos]

Before

All assets (logo.png, web_worker.js, desktop_icon.png) are bundled into every build, regardless of platform.

After

logo.png is included on all platforms.
web_worker.js is included only on web builds.
desktop_icon.png is included only on desktop builds.

Why this is useful

This significantly improves bundle size, prevents unused resources from being shipped, and gives developers better control over asset management.

Issues

Fixes #65065

Reviewer note

Would a design document be helpful for this change, or is the current explanation sufficient?

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.

Copilot

Pull Request Overview

This PR adds platform-specific asset filtering support to Flutter by introducing a new platforms field in pubspec.yaml asset entries. This allows developers to specify which platforms should include specific assets, reducing bundle sizes by excluding irrelevant assets from builds.

Adds platforms field to AssetsEntry class with validation for supported platform names
Implements platform filtering logic in the asset bundling process to skip assets not matching the target platform
Updates asset bundle entry constructors to include the new platforms parameter

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/flutter_tools/lib/src/flutter_manifest.dart	Adds platforms field parsing and validation to AssetsEntry
packages/flutter_tools/lib/src/asset.dart	Updates AssetBundleEntry and _Asset classes to support platforms field
packages/flutter_tools/lib/src/build_system/targets/assets.dart	Implements platform filtering logic during asset copying
packages/flutter_tools/lib/src/base/deferred_component.dart	Adds platforms display to deferred component output
packages/flutter_tools/lib/src/widget_preview/preview_pubspec_builder.dart	Preserves platforms field when transforming assets
packages/flutter_tools/test/general.shard/flutter_manifest_test.dart	Adds comprehensive tests for platforms field parsing and validation
packages/flutter_tools/test/general.shard/devfs_test.dart	Updates test asset bundle entries to include platforms parameter
packages/flutter_tools/test/general.shard/bundle_builder_test.dart	Updates test asset bundle entries to include platforms parameter

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packages/flutter_tools/lib/src/asset.dart

gemini-code-assist

Code Review

This pull request introduces a valuable feature for platform-specific asset filtering in pubspec.yaml, which can significantly improve bundle sizes. The implementation correctly propagates the new platforms field through the asset pipeline, from parsing in flutter_manifest.dart to the filtering logic in build_system/targets/assets.dart. The changes include necessary updates to data classes, equality checks, and hashing, and are accompanied by relevant tests. I have one suggestion to improve the efficiency and clarity of the platform validation logic.

packages/flutter_tools/lib/src/flutter_manifest.dart

bkonyi

Thanks for your contribution!

Overall, this LGTM with some minor comments that should be addressed.

packages/flutter_tools/lib/src/flutter_manifest.dart

packages/flutter_tools/test/general.shard/build_system/targets/assets_test.dart

packages/flutter_tools/lib/src/flutter_manifest.dart

packages/flutter_tools/lib/src/build_system/targets/assets.dart

hm21 · 2025-11-05T14:11:15Z

Ready for re-review.

FYI, the Linux tests are currently failing, but currently I don't think my changes are related. I quickly checked a few other new PRs and saw that the Linux tests failed for them as well. However, please let me know if you think my changes are the problem. I will look into it further.

bkonyi · 2025-11-05T14:58:31Z

Looks good to me! Thanks @hm21!

I think we're experiencing some infrastructure issues, so I don't think any of those Linux failures are the result of your change.

chingjun

Thank you for the fixes, this now looks a lot cleaner!

There is still an open question about what assets should be included in tests, but even with that unanswered I would still be ok landing this PR, and figure that out in the future.

The following are fully optional. It is out of scope for this PR, and is is fully optional whether you want to fix it in this PR, in a separate PR, or leave it for now.

The PR led me to think whether targetPlatform should still be an optional parameter in assetBundle.build(). Perhaps we should make it a required parameter.

Again, fully optional.

packages/flutter_tools/lib/src/asset.dart

hm21 · 2025-11-06T22:16:25Z

Okay targetPlatform is now required, so it’s ready for review. I think the PR is complete now, but if you have any other suggestions or ideas to extend it before merging, let me know. Thanks again for your reviews.

chingjun

LGTM!

One more minor nit, and you probably want to rebase your branch as it's now 200+ commits behind HEAD.

Thank you again for your contribution, and specifically for adding the changes to make the code base more robust. Thank you!

packages/flutter_tools/lib/src/asset.dart

fluttergithubbot · 2025-11-07T08:28:35Z

An existing Git SHA, 414d66bf4f353eea6e98e0c0d70a2db9bea9b9fc, was detected, and no actions were taken.

To re-trigger presubmits after closing or re-opeing a PR, or pushing a HEAD commit (i.e. with --force) that already was pushed before, push a blank commit (git commit --allow-empty -m "Trigger Build") or rebase to continue.

- Introduce `platforms` key in `flutter.assets` entries in pubspec.yaml to restrict assets to specific build targets (e.g. windows, android, ios, web). - Update asset loading logic in `asset.dart` and `targets/assets.dart` to skip assets not matching the current `TargetPlatform`. - Extend `flutter_manifest.dart` to parse and validate `platforms`. - Update preview pubspec builder and deferred component handling to be aware of platform-specific assets. - Add tests for manifest parsing, invalid platform values, and bundle builder behavior with platform-restricted assets. Example: ```yaml flutter: assets: - path: assets/icon.png platforms: [android, ios] ```

fluttergithubbot · 2025-11-07T08:46:40Z

An existing Git SHA, 414d66bf4f353eea6e98e0c0d70a2db9bea9b9fc, was detected, and no actions were taken.

To re-trigger presubmits after closing or re-opeing a PR, or pushing a HEAD commit (i.e. with --force) that already was pushed before, push a blank commit (git commit --allow-empty -m "Trigger Build") or rebase to continue.

chingjun · 2025-11-10T23:07:25Z

I just fixed the Google Testing for this PR. Good to be submitted now. @bkonyi do you want to take a final look at it before adding the autosubmit tag?

bkonyi · 2025-11-11T14:10:12Z

I just fixed the Google Testing for this PR. Good to be submitted now. @bkonyi do you want to take a final look at it before adding the autosubmit tag?

Thanks! I was going to take a look at that today :) I've approved the G3Fix and this change LGTM.

We should look into adding this feature to our documentation (filed #178294).

Thanks for your contribution @hm21!

…pec.yaml (flutter/flutter#176393)

…lutter#176393) ## Description This PR introduces platform-specific asset support in `pubspec.yaml`. Currently, Flutter does not allow specifying which platforms an asset should be included for. This results in all declared assets being bundled for every target platform, even if some are irrelevant (e.g. desktop-only or mobile-only images). ### What this PR changes - Adds a new optional `platforms` field under each asset in `pubspec.yaml`. - The field accepts a list of strings (platform identifiers, e.g. `["android", "ios", "web", "windows", "macos", "linux"]`). - Assets with a `platforms` restriction are only included in the bundle when building for a matching platform. - Invalid values (non-strings or unknown platform names) log an error. ### Example ```yaml flutter: assets: - path: assets/logo.png - path: assets/web_worker.js platforms: [web] - path: assets/desktop_icon.png platforms: [windows, linux, macos] ``` #### Before All assets (`logo.png`, `web_worker.js`, `desktop_icon.png`) are bundled into **every build**, regardless of platform. #### After - `logo.png` is included on all platforms. - `web_worker.js` is included only on web builds. - `desktop_icon.png` is included only on desktop builds. ### Why this is useful This significantly improves bundle size, prevents unused resources from being shipped, and gives developers better control over asset management. ## Issues Fixes flutter#65065 ## Reviewer note Would a design document be helpful for this change, or is the current explanation sufficient? ## 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. - [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. - [x] All existing and new tests are passing.  [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

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Document platform-specific asset filtering #178294

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rajveermalviya mentioned this pull request Nov 26, 2025

Upgrade Flutter and packages zulip/zulip-flutter#2009

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feat(assets): add platform-specific asset filtering in pubspec.yaml #176393

feat(assets): add platform-specific asset filtering in pubspec.yaml #176393

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