[flutter_tools] Reload widget-preview when data assets change by dcharkes · Pull Request #193437 · flutter/flutter

dcharkes · 2026-09-28T09:13:53Z

Previously, PreviewDetector and LspPreviewDetector ignored modifications to non-Dart files (and Dart files outside the analysis context, such as hook scripts), and FlutterHookResult._wasAnyFileModifiedSince did not treat deleted files (FileSystemEntityType.notFound) as modified.

Bug:

hook/build.dart Data assets support #146264

Changes

Add onNonDartFileChangeDetected callback to PreviewDetector and LspPreviewDetector, wired up in WidgetPreviewStartCommand to trigger a preview app restart when assetBundle.needsBuild() is true.
Treat FileSystemEntityType.notFound as modified in FlutterHookResult._wasAnyFileModifiedSince.
Update lsp_preview_detector_test.dart and asset_bundle_test.dart.

PR Stack

#	PR	Branch	Commit
1	#193434	`data-assets-empty-pubspec`	`ab37f42`
2	#193435	`data-assets-flutter-test`	`4956c97`
3	#193436	`data-assets-dev-dependencies-release-test`	`416d09a`
4	👉 #193437 (this PR)	`data-assets-widget-preview`	`431b96e`

Pre-launch Checklist

…mpty (flutter#193434) When `flutterManifest.isEmpty` (for example, a `pubspec.yaml` without a `flutter:` section), `ManifestAssetBundle.build` previously returned early with an empty `AssetManifest.bin`, ignoring any data assets produced by build/link hooks (`flutterHookResult.dataAssets`). Bug: * flutter#146264 ### Changes - Only short-circuit with an empty manifest in `ManifestAssetBundle.build` when both `flutterManifest.isEmpty` and `flutterHookResult?.dataAssets.isEmpty ?? true`. - Skip `computeTransitiveDependencies` when `flutterManifest.isEmpty`. - Add a unit test in `asset_bundle_test.dart` verifying that data assets from hooks are bundled when `pubspec.yaml` is empty. ### PR Stack | # | PR | Branch | Commit | | :-: | :--- | :--- | :--- | | **1** | **👉 flutter#193434 (this PR)** | `data-assets-empty-pubspec` | flutter@62199c4 | | 2 | flutter#193435 | `data-assets-flutter-test` | flutter@25be1ab | | 3 | flutter#193436 | `data-assets-dev-dependencies-release-test` | flutter@79abad9 | | 4 | flutter#193437 | `data-assets-widget-preview` | flutter@98f1001 | ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools. - [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 in-code documentation (doc comments with `///`). - [x] If this PR introduces a new feature or capability, I created and linked a website documentation issue or PR in [flutter/website] (or verified none is needed). - [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.

…r#193435) Previously, `flutter test` ran native assets hooks via `TestCompilerNativeAssetsBuilder.build(buildInfo)`, which only returned the `NativeAssetsManifest.json` URI and discarded the `FlutterHookResult` containing hook-generated data assets. Bug: * flutter#146264 ### Changes - Add `buildWithHookResult` to `TestCompilerNativeAssetsBuilder` returning both `nativeAssetsManifest` and `flutterHookResult`. - Pass `flutterHookResult` to `_buildTestAsset` / `assetBundle.build` in `TestCommand`. - Update `TestCommand._needsRebuild` to check if bundled asset files exist on disk, guard `pub.existsSync()`, and check `flutterHookResult.dependencies` modification timestamps. - Add a hermetic test in `test_test.dart` verifying that `flutter test` bundles data assets from hooks into `build/unit_test_assets`. ### PR Stack | # | PR | Branch | Commit | | :-: | :--- | :--- | :--- | | 1 | flutter#193434 | `data-assets-empty-pubspec` | flutter@62199c4 | | **2** | **👉 flutter#193435 (this PR)** | `data-assets-flutter-test` | flutter@390c757 | | 3 | flutter#193436 | `data-assets-dev-dependencies-release-test` | flutter@cca04e9 | | 4 | flutter#193437 | `data-assets-widget-preview` | flutter@0a5a8e9 | > **Note:** This PR is stacked on flutter#193434. To review only this PR's diff before the base PR lands, view commit flutter@390c757. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools. - [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 in-code documentation (doc comments with `///`). - [x] If this PR introduces a new feature or capability, I created and linked a website documentation issue or PR in [flutter/website] (or verified none is needed). - [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.

…n tests (flutter#193436) When running release-mode tests (such as `flutter test integration_test --release`), `createFlutterNativeAssetsBuildRunner` previously set `includeDevDependencies = !buildMode.isRelease`, which excluded hooks from `dev_dependencies`. Bug: * flutter#146264 ### Changes - Check `_isTestTarget(environment)` (whether `kTargetFile` is under `integration_test/`, `test_driver/`, or `test/`) so `includeDevDependencies` is `true` for test targets even in release mode. - Add a unit test in `native_assets_test.dart` verifying `includeDevDependencies` is `false` for `lib/main.dart` in release mode and `true` for `integration_test/app_test.dart`, `test_driver/app.dart`, and `test/app_test.dart`. ### PR Stack | # | PR | Branch | Commit | | :-: | :--- | :--- | :--- | | 1 | flutter#193434 | `data-assets-empty-pubspec` | flutter@ab37f42 | | 2 | flutter#193435 | `data-assets-flutter-test` | flutter@4956c97 | | **3** | **👉 flutter#193436 (this PR)** | `data-assets-dev-dependencies-release-test` | flutter@596124d | | 4 | flutter#193437 | `data-assets-widget-preview` | flutter@bd246d9 | ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools. - [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 in-code documentation (doc comments with `///`). - [x] If this PR introduces a new feature or capability, I created and linked a website documentation issue or PR in [flutter/website] (or verified none is needed). - [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.

gemini-code-assist

Code Review

This pull request adds support for triggering widget preview reloads when non-Dart files are modified by introducing an onNonDartFileChangeDetected callback to PreviewDetector and LspPreviewDetector. Review feedback recommends wrapping the asynchronous restart() call in unawaited to satisfy lint rules, and highlights a discrepancy where LspPreviewDetector fails to trigger the callback for Dart files outside the analysis context, such as hook scripts.

gemini-code-assist · 2026-10-12T13:27:44Z

+  void _onNonDartFileChangeDetected(String path) {
+    if (_widgetPreviewApp?.assetBundle.needsBuild() ?? false) {
+      logger.printStatus('Triggering reload based on update to asset: $path');
+      _widgetPreviewApp?.restart();
+    }
+  }


The restart() method on _widgetPreviewApp is asynchronous and returns a Future. To prevent unawaited futures and adhere to the project's lint rules (such as unawaited_futures), please wrap the call in unawaited.

Suggested change

void _onNonDartFileChangeDetected(String path) {

if (_widgetPreviewApp?.assetBundle.needsBuild() ?? false) {

logger.printStatus('Triggering reload based on update to asset: $path');

_widgetPreviewApp?.restart();

}

}

void _onNonDartFileChangeDetected(String path) {

if (_widgetPreviewApp?.assetBundle.needsBuild() ?? false) {

logger.printStatus('Triggering reload based on update to asset: $path');

unawaited(_widgetPreviewApp?.restart());

}

}

Done — switched to unawaited(_triggerReload(.hotReload)); to match the other reload callbacks.

gemini-code-assist · 2026-10-12T13:27:44Z

    if (!filePath.isDartFile) {
+      onNonDartFileChangeDetected?.call(filePath);
      return;
    }


In LspPreviewDetector, Dart files that are outside the analysis context (such as hook scripts) will bypass the !filePath.isDartFile check and will not trigger onNonDartFileChangeDetected. This is a discrepancy from PreviewDetector (which catches them via StateError on _collection.contextFor(eventPath)). As a result, modifications to hook scripts won't trigger a rebuild/restart when using the LSP preview detector.

AI response: In LspPreviewDetector._fileAddedOrUpdated, all .dart file changes (including hook scripts) proceed to waitForAnalysis(), fetch dtd.getFlutterWidgetPreviews(), and invoke onChangeDetected(result), which triggers _triggerReload(.hotReload) and rebuilds the asset bundle when assetBundle.needsBuild() is true. PreviewDetector only needed onNonDartFileChangeDetected in its on StateError catch block because _collection.contextFor(eventPath) returns early before onChangeDetected for excluded Dart files.

github-actions Bot added the tool Affects the "flutter" command-line tool. See also t: labels. label Sep 28, 2026

This was referenced Sep 28, 2026

[flutter_tools] Include data assets from hooks when pubspec.yaml is empty #193434

Merged

[flutter_tools] Bundle data assets from hooks in flutter test #193435

Merged

[flutter_tools] Include dev_dependencies hooks for release integration tests #193436

Merged

dcharkes force-pushed the data-assets-widget-preview branch from d677123 to 98f1001 Compare September 28, 2026 09:58

dcharkes added the CICD Run CI/CD label Sep 28, 2026

dcharkes requested a review from bkonyi September 28, 2026 10:27

dcharkes force-pushed the data-assets-widget-preview branch 6 times, most recently from 54b2687 to 8d7fa09 Compare October 1, 2026 09:40

dcharkes force-pushed the data-assets-widget-preview branch 2 times, most recently from 7ffc4e8 to bd246d9 Compare October 6, 2026 08:15

dcharkes force-pushed the data-assets-widget-preview branch from bd246d9 to cdc64dd Compare October 12, 2026 13:26

dcharkes marked this pull request as ready for review October 12, 2026 13:26

gemini-code-assist Bot reviewed Oct 12, 2026

View reviewed changes

[flutter_tools] Reload widget-preview when data assets change

431b96e

dcharkes force-pushed the data-assets-widget-preview branch from cdc64dd to 431b96e Compare October 12, 2026 13:57

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[flutter_tools] Reload widget-preview when data assets change - #193437

[flutter_tools] Reload widget-preview when data assets change#193437
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dcharkes commented Sep 28, 2026 •

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dcharkes commented Sep 28, 2026 •

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