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[ Widget Preview ] Use analysis server for widget preview detection#184473

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bkonyi:widget_preview_analysis_server_implementation
Apr 2, 2026
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[ Widget Preview ] Use analysis server for widget preview detection#184473
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bkonyi:widget_preview_analysis_server_implementation

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@bkonyi bkonyi commented Apr 1, 2026

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This change ports the flutter widget-preview start command to utilize the Dart Analysis Server to detect widget previews in projects. When launched from an IDE, the widget previewer will use the existing DAS and DTD instances, greatly reducing the amount of memory consumed by the widget previewer.

A --legacy-preview-detection flag has also been added to fall back to the previous in-process preview detection logic. This flag will be removed in a future release once the DAS implementation is proven to be stable.

Fixes #179584

@bkonyi
[ Widget Preview ] Use analysis server for widget preview detection
6ace28a 
This change ports the `flutter widget-preview start` command to utilize
the Dart Analysis Server to detect widget previews in projects. When
launched from an IDE, the widget previewer will use the existing DAS
and DTD instances, greatly reducing the amount of memory consumed by the
widget previewer.

A `--legacy-preview-detection` flag has also been added to fall back to
the previous in-process preview detection logic. This flag will be
removed in a future release once the DAS implementation is proven to be
stable.

Fixes flutter#179584
@bkonyi bkonyi added the CICD Run CI/CD label Apr 1, 2026
@bkonyi bkonyi requested a review from jyameo April 1, 2026 18:30
@github-actions github-actions Bot added the tool Affects the "flutter" command-line tool. See also t: labels. label Apr 1, 2026
bkonyi
bkonyi commented Apr 1, 2026
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Comment thread packages/flutter_tools/lib/src/widget_preview/dtd_types.dart

/// The set of widget previews defined in a script of an analyzed Flutter
/// project.
class FlutterWidgetPreviews {

@bkonyi bkonyi Apr 1, 2026

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This file is basically a slightly modified version of the changes made in https://dart-review.googlesource.com/c/sdk/+/478100/11/third_party/pkg/language_server_protocol/lib/protocol_custom_generated.dart

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Code Review

This pull request introduces LSP-based preview detection for the widget previewer, allowing it to leverage the analysis server for more robust preview discovery. Key changes include the addition of LspPreviewDetector and FlutterWidgetPreviews data structures, updates to WidgetPreviewStartCommand to support both legacy and LSP-based detection modes, and the addition of necessary DTD service methods. Several improvements were suggested to ensure data consistency, null safety, and adherence to Dart best practices for class definitions.

Comment thread packages/flutter_tools/lib/src/widget_preview/dtd_types.dart
Comment thread packages/flutter_tools/lib/src/widget_preview/preview_code_generator.dart
Comment thread packages/flutter_tools/lib/src/widget_preview/dtd_types.dart Outdated
Comment thread packages/flutter_tools/lib/src/widget_preview/dtd_types.dart Outdated
Comment thread packages/flutter_tools/lib/src/widget_preview/dtd_types.dart Outdated
@github-actions github-actions Bot removed the CICD Run CI/CD label Apr 1, 2026
@bkonyi bkonyi added the CICD Run CI/CD label Apr 1, 2026
@github-actions github-actions Bot removed the CICD Run CI/CD label Apr 1, 2026
@bkonyi bkonyi added the CICD Run CI/CD label Apr 1, 2026
@github-actions github-actions Bot removed the CICD Run CI/CD label Apr 1, 2026
@bkonyi bkonyi added the CICD Run CI/CD label Apr 1, 2026
jyameo
jyameo approved these changes Apr 2, 2026
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overall lgtm!

Comment thread packages/flutter_tools/lib/src/widget_preview/preview_code_generator.dart
);
}
_imports.addAll({
for (final MapEntry(:key, :value) in imports.entries) key: int.parse(value.substring(2)),

@jyameo jyameo Apr 2, 2026

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nit: it might safer to use tryParse or a check to avoid throwing an exception if value doesn't follow the expected format for some reason.

@bkonyi bkonyi Apr 2, 2026

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Normally I'd agree, but in this situation I think it's better to throw an exception so we can get a signal that the analyzer is returning a poorly formatted response since this should always be an integer.

@bkonyi bkonyi added the autosubmit Merge PR when tree becomes green via auto submit App label Apr 2, 2026
@auto-submit auto-submit Bot added this pull request to the merge queue Apr 2, 2026
Merged via the queue into flutter:master with commit 02f8ea2 Apr 2, 2026
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@flutter-dashboard flutter-dashboard Bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Apr 2, 2026
@bkonyi bkonyi deleted the widget_preview_analysis_server_implementation branch April 2, 2026 19:19
engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Apr 3, 2026
@engine-flutter-autoroll
02f8ea250 [ Widget Preview ] Use analysis server for widget preview d…
56a87fa 
…etection (flutter/flutter#184473)
@engine-flutter-autoroll engine-flutter-autoroll mentioned this pull request Apr 3, 2026
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auto-submit Bot pushed a commit to flutter/packages that referenced this pull request Apr 3, 2026
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Roll Flutter from 0f401eea0439 to 7245c3f71104 (25 revisions) (#11427)
a95e1c3 
flutter/flutter@0f401ee...7245c3f

2026-04-03 [email protected] Roll Skia from c07c67045b6d to 5d847ba5c4aa (1 revision) (flutter/flutter#184570)
2026-04-03 [email protected] Roll Dart SDK from 3c7a79045b8b to 46f49142acd9 (1 revision) (flutter/flutter#184567)
2026-04-03 [email protected] Roll ICU from ee5f27adc28b to ff7995a708a1 (5 revisions) (flutter/flutter#184566)
2026-04-03 [email protected] Roll Skia from 9ae8231be181 to c07c67045b6d (4 revisions) (flutter/flutter#184562)
2026-04-03 [email protected] Roll Fuchsia Linux SDK from BFLjk6Uwd0gs_Hkdk... to PpL3Bn2YMb2h9LbdK... (flutter/flutter#184556)
2026-04-03 [email protected] Roll Skia from 0566b2f5f0d1 to 9ae8231be181 (1 revision) (flutter/flutter#184547)
2026-04-03 [email protected] Roll Dart SDK from 6008eaddd589 to 3c7a79045b8b (3 revisions) (flutter/flutter#184551)
2026-04-03 [email protected] Fix wide gamut macos integration test (flutter/flutter#184427)
2026-04-02 [email protected] forward an application name to DDS (flutter/flutter#184459)
2026-04-02 [email protected] Roll Skia from 973117cfa875 to 0566b2f5f0d1 (8 revisions) (flutter/flutter#184534)
2026-04-02 [email protected] Support different joins for stroked rects in uber_sdf, fix incorrect aa (flutter/flutter#184395)
2026-04-02 [email protected] [ Widget Preview ] Handle collections and records in custom preview annotations (flutter/flutter#184518)
2026-04-02 [email protected] Moves android_semantics_integration_test out of staging (flutter/flutter#184079)
2026-04-02 [email protected] Roll Packages from b3fcf14 to 66bf7ec (4 revisions) (flutter/flutter#184514)
2026-04-02 [email protected] Fix line breaks being lost when copying after selection gesture in SelectableRegion (flutter/flutter#184421)
2026-04-02 [email protected] Add plugin version to SwiftPM package symlink directory (flutter/flutter#183668)
2026-04-02 [email protected] Add our own wrapper for `CommonExtension` due to change in signature from 8.x->9.0 (flutter/flutter#184433)
2026-04-02 [email protected] [Android] Use EdgeToEdge.enable/WindowCompat for edge-to-edge mode instead of deprecated View flags (flutter/flutter#183072)
2026-04-02 [email protected] [data_assets] Cleanup tests (flutter/flutter#184209)
2026-04-02 [email protected] Enable SPM by default on Stable (flutter/flutter#184495)
2026-04-02 [email protected] Roll Dart SDK from d84bdfeb45eb to 6008eaddd589 (2 revisions) (flutter/flutter#184513)
2026-04-02 [email protected] Reland "Even more awaits" (flutter/flutter#184467)
2026-04-02 [email protected] Roll Skia from bb9fd8653739 to 973117cfa875 (2 revisions) (flutter/flutter#184498)
2026-04-02 [email protected] [ Widget Preview ] Use analysis server for widget preview detection (flutter/flutter#184473)
2026-04-02 [email protected] [web_ui] Fix avoid_type_to_string lint violation (flutter/flutter#184342)

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@Piinks Piinks mentioned this pull request Apr 3, 2026
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mbcorona pushed a commit to mbcorona/flutter that referenced this pull request Apr 15, 2026
@bkonyi @mbcorona
[ Widget Preview ] Use analysis server for widget preview detection (f…
164c70c 
…lutter#184473)

This change ports the `flutter widget-preview start` command to utilize
the Dart Analysis Server to detect widget previews in projects. When
launched from an IDE, the widget previewer will use the existing DAS and
DTD instances, greatly reducing the amount of memory consumed by the
widget previewer.

A `--legacy-preview-detection` flag has also been added to fall back to
the previous in-process preview detection logic. This flag will be
removed in a future release once the DAS implementation is proven to be
stable.

Fixes flutter#179584
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Process dart:flutter_tools.snapshot and dart:frontend_server_aot.dart.snapshot consumes huge memory on macOS when flutter run even has stopped

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