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[widget-preview] Generated Scaffold project doesn't work with pub workspaces #169268

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#171538
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[widget-preview] Generated Scaffold project doesn't work with pub workspaces#169268
#171538
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bkonyi
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P1High-priority issues at the top of the work lista: widget previewsIssues related to the Widget Previewer toolingfound in release: 3.32Found to occur in 3.32found in release: 3.33Found to occur in 3.33has reproducible stepsThe issue has been confirmed reproducible and is ready to work onr: fixedIssue is closed as already fixed in a newer versionteam-toolOwned by Flutter Tool teamtoolAffects the "flutter" command-line tool. See also t: labels.triaged-toolTriaged by Flutter Tool team
@benthillerkus

Description

@benthillerkus
benthillerkus
opened on May 22, 2025

Steps to reproduce

  1. Make sure flutter devices lists Google Chrome, otherwise the widget previews will not work
  2. Create a new empty pub workspace
  3. Create a new flutter project in a subfolder of that workspace using flutter create
  4. Make sure to set resolution: workspace in the new flutter project
  5. Make sure to add the new flutter project to the workspace list of packages
  6. Add the following sample widget preview to lib/main.dart in the new flutter project:
@Preview()
Widget preview() => Text("test");
  1. Run flutter pub get (from the workspace root)
  2. Run flutter widget-preview start (from the workspace root)

Expected results

The Widget previews page should open in the browser

Actual results

The command fails with a compile error because the import cannot be resolved:

See these GitHub Actions workflow run results: https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039

Code sample

https://github.com/benthillerkus/widget-preview-repro-workspaces

Screenshots or Video

Screenshots / Video demonstration

[Upload media here]

Logs

Logs 
Downloading Web SDK...
Creating widget preview scaffolding at: /home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces/.dart_tool/widget_preview_scaffold
  .dart_tool/widget_preview_scaffold/web/favicon.png (created)
  .dart_tool/widget_preview_scaffold/web/icons/Icon-maskable-192.png (created)
  .dart_tool/widget_preview_scaffold/web/icons/Icon-192.png (created)
  .dart_tool/widget_preview_scaffold/web/icons/Icon-512.png (created)
  .dart_tool/widget_preview_scaffold/web/icons/Icon-maskable-512.png (created)
  .dart_tool/widget_preview_scaffold/web/index.html (created)
  .dart_tool/widget_preview_scaffold/web/manifest.json (created)
  .dart_tool/widget_preview_scaffold/analysis_options.yaml (created)
  .dart_tool/widget_preview_scaffold/lib/main.dart (created)
  .dart_tool/widget_preview_scaffold/pubspec.yaml (created)
  .dart_tool/widget_preview_scaffold/.gitignore (created)
  .dart_tool/widget_preview_scaffold/.idea/modules.xml (created)
  .dart_tool/widget_preview_scaffold/.idea/libraries/KotlinJavaRuntime.xml (created)
  .dart_tool/widget_preview_scaffold/.idea/libraries/Dart_SDK.xml (created)
  .dart_tool/widget_preview_scaffold/.idea/workspace.xml (created)
  .dart_tool/widget_preview_scaffold/.idea/runConfigurations/main_dart.xml (created)
  .dart_tool/widget_preview_scaffold/widget_preview_scaffold.iml (created)
  .dart_tool/widget_preview_scaffold/README.md (created)
  .dart_tool/widget_preview_scaffold/lib/src/widget_preview_rendering.dart (created)
  .dart_tool/widget_preview_scaffold/lib/src/dtd_services.dart (created)
  .dart_tool/widget_preview_scaffold/lib/src/generated_preview.dart (created)
  .dart_tool/widget_preview_scaffold/lib/src/controls.dart (created)
  .dart_tool/widget_preview_scaffold/lib/src/widget_preview.dart (created)
  .dart_tool/widget_preview_scaffold/lib/src/utils.dart (created)
Creating the Widget Preview Scaffold manifest at /home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces/.dart_tool/widget_preview_scaffold/preview_manifest.json
Resolving dependencies in `.dart_tool/widget_preview_scaffold`...
Downloading packages...
Got dependencies in `.dart_tool/widget_preview_scaffold`.
Resolving dependencies in `/home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces/.dart_tool/widget_preview_scaffold`...
Downloading packages...
  json_rpc_2 3.0.3 (4.0.0 available)
  lints 5.1.1 (6.0.0 available)
  material_color_utilities 0.11.1 (0.12.0 available)
  meta 1.16.0 (1.17.0 available)
  test_api 0.7.4 (0.7.6 available)
  vector_math 2.1.4 (2.2.0 available)
  vm_service 15.0.0 (15.0.1 available)
+ workspace 0.0.0 from path .
Changed 1 dependency in `/home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces/.dart_tool/widget_preview_scaffold`!
7 packages have newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.
"dtd" is already in "dependencies". Will try to update the constraint.
"flutter_lints" is already in "dependencies". Will try to update the constraint.
"stack_trace" is already in "dependencies". Will try to update the constraint.
"url_launcher" is already in "dependencies". Will try to update the constraint.
Resolving dependencies in `/home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces/.dart_tool/widget_preview_scaffold`...
Downloading packages...
  json_rpc_2 3.0.3 (4.0.0 available)
  lints 5.1.1 (6.0.0 available)
  material_color_utilities 0.11.1 (0.12.0 available)
  meta 1.16.0 (1.17.0 available)
  test_api 0.7.4 (0.7.6 available)
  vector_math 2.1.4 (2.2.0 available)
  vm_service 15.0.0 (15.0.1 available)
Got dependencies in `/home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces/.dart_tool/widget_preview_scaffold`!
7 packages have newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.
Resolving dependencies in `.dart_tool/widget_preview_scaffold`...
Downloading packages...
Got dependencies in `.dart_tool/widget_preview_scaffold`.
Finding previews in /home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces...
Found 1 preview.
Launching the Widget Preview Scaffold...
[{"event":"daemon.connected","params":{"version":"0.6.1","pid":2616}}]
[{"event":"app.start","params":{"appId":"d9e[8](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:9)0c6b-7f66-4aa9-ba54-5dd50b99bf23","deviceId":"chrome","directory":"/home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces/.dart_tool/widget_preview_scaffold","supportsRestart":true,"launchMode":"run","mode":"debug"}}]
Launching lib/main.dart on Chrome in debug mode...
[{"event":"app.progress","params":{"appId":"d[9](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:10)e80c6b-7f66-4aa9-ba54-5dd50b99bf23","id":"1","progressId":null,"message":"Waiting for connection from debug service on Chrome...","finished":false}}]
Error: Couldn't resolve the package 'test' in 'package:test/main.dart'.
lib/src/generated_preview.dart:3:8: Error: Not found: 'package:test/main.dart'
import 'package:test/main.dart' as _i2;
       ^
lib/src/generated_preview.dart:6:43: Error: Method not found: 'preview'.
    [_i1.WidgetPreview(builder: () => _i2.preview())];
                                          ^^^^^^^
Unhandled exception:
Unsupported operation: Unsupported invalid type InvalidType(<invalid>) (InvalidType). Encountered while compiling file:///home/runner/work/widget-preview-repro-workspaces/widget-preview-repro-workspaces/.dart_tool/widget_preview_scaffold/lib/src/generated_preview.dart, which contains the type: FunctionType(<invalid> Function()).
#0      LibraryCompiler._typeCompilationError (package:dev_compiler/src/kernel/compiler_new.dart:3930)
#1      LibraryCompiler._emitType (package:dev_compiler/src/kernel/compiler_new.dart:3899)
#2      LibraryCompiler._emitFunctionTagged (package:dev_compiler/src/kernel/compiler_new.dart:3773)
#3      LibraryCompiler.visitFunctionExpression (package:dev_compiler/src/kernel/compiler_new.dart:7825)
#4      FunctionExpression.accept (package:kernel/src/ast/expressions.dart:4608)
#5      LibraryCompiler._visitExpression (package:dev_compiler/src/kernel/compiler_new.dart:4508)
#6      LibraryCompiler._emitNamedExpression (package:dev_compiler/src/kernel/compiler_new.dart:7090)
#7      LibraryCompiler._emitArgumentGroups (package:dev_compiler/src/kernel/compiler_new.dart:7078)
#8      LibraryCompiler._emitArgumentList (package:dev_compiler/src/kernel/compiler_new.dart:7041)
#9      LibraryCompiler.visitConstructorInvocation (package:dev_compiler/src/kernel/compiler_new.dart:7306)
#[10](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:11)     ConstructorInvocation.accept (package:kernel/src/ast/expressions.dart:2686)
#[11](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:12)     LibraryCompiler._visitExpression (package:dev_compiler/src/kernel/compiler_new.dart:4508)
#[12](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:13)     MappedIterable.elementAt (dart:_internal/iterable.dart:402)
#13     ListIterator.moveNext (dart:_internal/iterable.dart:371)
#14     new _GrowableList._ofEfficientLengthIterable (dart:core-patch/growable_array.dart:194)
#15     new _GrowableList.of (dart:core-patch/growable_array.dart:154)
#16     new List.of (dart:core-patch/array_patch.dart:39)
#17     SetBase.toList (dart:collection/set.dart:119)
#18     LibraryCompiler._visitExpressionList (package:dev_compiler/src/kernel/compiler_new.dart:4471)
#19     LibraryCompiler.visitListLiteral (package:dev_compiler/src/kernel/compiler_new.dart:7699)
#20     ListLiteral.accept (package:kernel/src/ast/expressions.dart:4162)
#21     LibraryCompiler._visitExpression (package:dev_compiler/src/kernel/compiler_new.dart:4508)
#22     LibraryCompiler.visitReturnStatement (package:dev_compiler/src/kernel/compiler_new.dart:5220)
#23     ReturnStatement.accept (package:kernel/src/ast/statements.dart:1076)
#24     LibraryCompiler._visitStatement (package:dev_compiler/src/kernel/compiler_new.dart:44[13](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:14))
#25     LibraryCompiler._emitFunctionScopedBody (package:dev_compiler/src/kernel/compiler_new.dart:4446)
#26     LibraryCompiler._emitFunction.<anonymous closure> (package:dev_compiler/src/kernel/compiler_new.dart:4094)
#27     LibraryCompiler._withLetScope (package:dev_compiler/src/kernel/compiler_new.dart:3191)
#28     LibraryCompiler._withCurrentFunction (package:dev_compiler/src/kernel/compiler_new.dart:4225)
#29     LibraryCompiler._emitFunction (package:dev_compiler/src/kernel/compiler_new.dart:4087)
#30     LibraryCompiler._emitLibraryFunction (package:dev_compiler/src/kernel/compiler_new.dart:3707)
#31     LibraryCompiler._emitLibraryMembers (package:dev_compiler/src/kernel/compiler_new.dart:3565)
#32     LibraryCompiler._emitLibrary (package:dev_compiler/src/kernel/compiler_new.dart:1164)
#33     LibraryCompiler.emitLibrary (package:dev_compiler/src/kernel/compiler_new.dart:822)
#34     LibraryBundleCompiler.emitModule (package:dev_compiler/src/kernel/compiler_new.dart:157)
#35     IncrementalJavaScriptBundler.compile (package:frontend_server/src/javascript_bundle.dart:259)
#36     FrontendCompiler.writeJavaScriptBundle (package:frontend_server/frontend_server.dart:875)
<asynchronous suspension>
#37     FrontendCompiler.compile (package:frontend_server/frontend_server.dart:690)
<asynchronous suspension>
#38     listenAndCompile.<anonymous closure> (package:frontend_server/frontend_server.dart:1399)
<asynchronous suspension>
[{"event":"app.stop","params":{"appId":"d9e80c6b-7f66-4aa9-ba54-5dd50b99bf23","error":"The Dart compiler exited unexpectedly.","trace":"#0      throwToolExit (package:flutter_tools/src/base/common.dart:34:3)\n#1      DefaultResidentCompiler._compile.<anonymous closure> (package:flutter_tools/src/compile.dart:894:15)\n#2      _rootRun (dart:async/zone.dart:1517:47)\n#3      _CustomZone.run (dart:async/zone.dart:[14](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:15)22:19)\n#4      _CustomZone.runGuarded (dart:async/zone.dart:1321:7)\n#5      _BufferingStreamSubscription._sendDone.sendDone (dart:async/stream_impl.dart:434:13)\n#6      _BufferingStreamSubscription._sendDone (dart:async/stream_impl.dart:444:7)\n#7      _BufferingStreamSubscription._close (dart:async/stream_impl.dart:333:7)\n#8      _SinkTransformerStreamSubscription._close (dart:async/stream_transformers.dart:91:11)\n#9      _EventSinkWrapper.close (dart:async/stream_transformers.dart:21:11)\n#10     _StringAdapterSink.close (dart:convert/string_conversion.dart:241:11)\n#11     _LineSplitterSink.close (dart:convert/line_splitter.dart:144:11)\n#12     _SinkTransformerStreamSubscription._handleDone (dart:async/stream_transformers.dart:136:24)\n#13     _rootRun (dart:async/zone.dart:[15](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:16)17:47)\n#14     _CustomZone.run (dart:async/zone.dart:1422:19)\n#15     _CustomZone.runGuarded (dart:async/zone.dart:1321:7)\n#[16](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:17)     _BufferingStreamSubscription._sendDone.sendDone (dart:async/stream_impl.dart:434:13)\n#[17](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:18)     _BufferingStreamSubscription._sendDone (dart:async/stream_impl.dart:444:7)\n#[18](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:19)     _BufferingStreamSubscription._close (dart:async/stream_impl.dart:333:7)\n#[19](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:20)     _SinkTransformerStreamSubscription._close (dart:async/stream_transformers.dart:91:11)\n#[20](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:21)     _EventSinkWrapper.close (dart:async/stream_transformers.dart:[21](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:22):11)\n#21     _StringAdapterSink.close (dart:convert/string_conversion.dart:241:11)\n#[22](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:23)     _Utf8ConversionSink.close (dart:convert/string_conversion.dart:301:20)\n#[23](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:24)     _ConverterStreamEventSink.close (dart:convert/chunked_conversion.dart:79:18)\n#[24](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:25)     _SinkTransformerStreamSubscription._handleDone (dart:async/stream_transformers.dart:136:24)\n#[25](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:26)     _rootRun (dart:async/zone.dart:1517:47)\n#26     _CustomZone.run (dart:async/zone.dart:1422:19)\n#27     _CustomZone.runGuarded (dart:async/zone.dart:1321:7)\n#28     _BufferingStreamSubscription._sendDone.sendDone (dart:async/stream_impl.dart:434:13)\n#29     _BufferingStreamSubscription._sendDone (dart:async/stream_impl.dart:444:7)\n#30     _BufferingStreamSubscription._close (dart:async/stream_impl.dart:333:7)\n#31     _SyncStreamControllerDispatch._sendDone (dart:async/stream_controller.dart:806:19)\n#32     _StreamController._closeUnchecked (dart:async/stream_controller.dart:652:7)\n#33     _StreamController.close (dart:async/stream_controller.dart:645:5)\n#34     _Socket._onData (dart:io-patch/socket_patch.dart:2912:21)\n#35     _rootRunUnary (dart:async/zone.dart:1546:13)\n#36     _CustomZone.runUnary (dart:async/zone.dart:1429:19)\n#37     _CustomZone.runUnaryGuarded (dart:async/zone.dart:1329:7)\n#38     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:381:11)\n#39     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:312:7)\n#40     _SyncStreamControllerDispatch._sendData (dart:async/stream_controller.dart:798:19)\n#41     _StreamController._add (dart:async/stream_controller.dart:663:7)\n#42     _StreamController.add (dart:async/stream_controller.dart:618:5)\n#43     new _RawSocket.<anonymous closure> (dart:io-patch/socket_patch.dart:2331:33)\n#44     _NativeSocket.issueReadEvent.issue (dart:io-patch/socket_patch.dart:1641:18)\n#45     _microtaskLoop (dart:async/schedule_microtask.dart:42:23)\n#46     _startMicrotaskLoop (dart:async/schedule_microtask.dart:60:5)\n#47     _runPendingImmediateCallback (dart:isolate-patch/isolate_patch.dart:1[27](https://github.com/benthillerkus/widget-preview-repro-workspaces/actions/runs/15186404039/job/42707786840#step:6:28):13)\n#48     _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:194:5)\n"}}]
Failed to compile application.
[{"event":"app.progress","params":{"appId":"d9e80c6b-7f66-4aa9-ba54-5dd50b99bf23","id":"2","progressId":null,"message":"Waiting for Flutter DevTools to be served...","finished":false}}]
Done loading previews.
[{"event":"app.progress","params":{"appId":"d9e80c6b-7f66-4aa9-ba54-5dd50b99bf23","id":"1","progressId":null,"finished":true}}]
Failed to launch the widget previewer.
Error: Process completed with exit code 1.

Flutter Doctor output

Doctor output 
[✓] Flutter (Channel stable, 3.32.0, on macOS 15.5 24F74 darwin-arm64, locale en-DE) [558ms]
    • Flutter version 3.32.0 on channel stable at /Users/bent/.puro/envs/stable/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision be698c48a6 (3 days ago), 2025-05-19 12:59:14 -0700
    • Engine revision 1881800949
    • Dart version 3.8.0
    • DevTools version 2.45.1

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0) [1,489ms]
    • Android SDK at /Users/bent/Library/Android/sdk
    • Platform android-35, build-tools 34.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 16.2) [1,042ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 16C5032a
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web [12ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2024.1) [12ms]
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)

[✓] VS Code (version 1.100.2) [11ms]
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.110.0

[✓] Connected device (2 available) [6.3s]
    • macOS (desktop) • macos  • darwin-arm64   • macOS 15.5 24F74 darwin-arm64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 137.0.7151.41
    ! Error: Browsing on the local area network for iPad von The. Ensure the device is unlocked and attached with a cable or associated with the same local area network as this Mac.
      The device must be opted into Developer Mode to connect wirelessly. (code -27)

[✓] Network resources [318ms]
    • All expected network resources are available.

• No issues found!

^^ This is the output from my local dev machine, but please note that I was able to reproduce the issue setup on a matrix of Windows, macOS, Ubuntu, Flutter stable channel and master channel on GitHub Actions, so the issue is not related any local issues on my machine.

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P1High-priority issues at the top of the work lista: widget previewsIssues related to the Widget Previewer toolingfound in release: 3.32Found to occur in 3.32found in release: 3.33Found to occur in 3.33has reproducible stepsThe issue has been confirmed reproducible and is ready to work onr: fixedIssue is closed as already fixed in a newer versionteam-toolOwned by Flutter Tool teamtoolAffects the "flutter" command-line tool. See also t: labels.triaged-toolTriaged by Flutter Tool team

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