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[ Widget Preview ] @Preview() applications outside of lib/ cause the previewer to crash #178651

Description

@denivyruck

Found 1 preview.

Oops; flutter has exited unexpectedly: "Null check operator used on a null value".
A crash report has been written to

Command

flutter widget-preview start

Steps to Reproduce

  1. ...
  2. ...
  3. ...

Logs

_TypeError: (#0 PreviewCodeGenerator._buildPreviews (package:flutter_tools/src/widget_preview/preview_code_generator.dart:167:58))

#0      PreviewCodeGenerator._buildPreviews (package:flutter_tools/src/widget_preview/preview_code_generator.dart:167:58)
#1      PreviewCodeGenerator._buildGeneratedPreviewMethod (package:flutter_tools/src/widget_preview/preview_code_generator.dart:145:13)
#2      PreviewCodeGenerator.populatePreviewsInGeneratedPreviewScaffold.<anonymous closure>.<anonymous closure> (package:flutter_tools/src/widget_preview/preview_code_generator.dart:109:37)
#3      _$MethodBuilder.update (package:code_builder/src/specs/method.g.dart:332:33)
#4      new _$Method (package:code_builder/src/specs/method.g.dart:38:29)
#5      PreviewCodeGenerator.populatePreviewsInGeneratedPreviewScaffold.<anonymous closure> (package:flutter_tools/src/widget_preview/preview_code_generator.dart:108:14)
#6      _$LibraryBuilder.update (package:code_builder/src/specs/library.g.dart:232:33)
#7      new _$Library (package:code_builder/src/specs/library.g.dart:28:30)
#8      PreviewCodeGenerator.populatePreviewsInGeneratedPreviewScaffold (package:flutter_tools/src/widget_preview/preview_code_generator.dart:104:20)
#9      WidgetPreviewStartCommand.runCommand (package:flutter_tools/src/commands/widget_preview.dart:341:27)
<asynchronous suspension>
#10     FlutterCommand.run.<anonymous closure> (package:flutter_tools/src/runner/flutter_command.dart:1559:27)
<asynchronous suspension>
#11     AppContext.run.<anonymous closure> (package:flutter_tools/src/base/context.dart:154:19)
<asynchronous suspension>
#12     CommandRunner.runCommand (package:args/command_runner.dart:212:13)
<asynchronous suspension>
#13     FlutterCommandRunner.runCommand.<anonymous closure> (package:flutter_tools/src/runner/flutter_command_runner.dart:487:9)
<asynchronous suspension>
#14     AppContext.run.<anonymous closure> (package:flutter_tools/src/base/context.dart:154:19)
<asynchronous suspension>
#15     FlutterCommandRunner.runCommand (package:flutter_tools/src/runner/flutter_command_runner.dart:422:5)
<asynchronous suspension>
#16     run.<anonymous closure>.<anonymous closure> (package:flutter_tools/runner.dart:101:11)
<asynchronous suspension>
�[32m[✓]�[39m Flutter (Channel stable, 3.38.1, on Microsoft Windows [Version 10.0.26200.7171], locale en-US) [278ms]
    �[32m•�[39m Flutter version 3.38.1 on channel stable at C:\Users\DenivyBraiamRuck\dependencies\flutter
    �[32m•�[39m Upstream repository https://github.com/flutter/flutter.git
    �[32m•�[39m Framework revision b45fa18946 (4 days ago), 2025-11-12 22:09:06 -0600
    �[32m•�[39m Engine revision b5990e5ccc
    �[32m•�[39m Dart version 3.10.0
    �[32m•�[39m DevTools version 2.51.1
    �[32m•�[39m Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android,
      enable-ios, cli-animations, enable-native-assets, omit-legacy-version-file, enable-lldb-debugging

�[32m[✓]�[39m Windows Version (Windows 11 or higher, 25H2, 2009) [1,131ms]

�[32m[✓]�[39m Android toolchain - develop for Android devices (Android SDK version 36.1.0) [2.8s]
    �[32m•�[39m Android SDK at C:\Users\DenivyBraiamRuck\AppData\Local\Android\sdk
    �[32m•�[39m Emulator version 36.2.12.0 (build_id 14214601) (CL:N/A)
    �[32m•�[39m Platform android-36, build-tools 36.1.0
    �[32m•�[39m Java binary at: C:\Program Files\Android\Android Studio\jbr\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"`.
    �[32m•�[39m Java version OpenJDK Runtime Environment (build 21.0.8+-14196175-b1038.72)
    �[32m•�[39m All Android licenses accepted.

�[32m[✓]�[39m Chrome - develop for the web [9ms]
    �[32m•�[39m Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

�[31m[✗]�[39m Visual Studio - develop Windows apps [8ms]
    �[31m✗�[39m Visual Studio not installed; this is necessary to develop Windows apps.
      Download at https://visualstudio.microsoft.com/downloads/.
      Please install the "Desktop development with C++" workload, including all of its default components

�[32m[✓]�[39m Connected device (4 available) [652ms]
    �[32m•�[39m sdk gphone64 x86 64 (mobile) • emulator-5554 • android-x64    • Android 16 (API 36) (emulator)
    �[32m•�[39m Windows (desktop)            • windows       • windows-x64    • Microsoft Windows [Version 10.0.26200.7171]
    �[32m•�[39m Chrome (web)                 • chrome        • web-javascript • Google Chrome 142.0.7444.163
    �[32m•�[39m Edge (web)                   • edge          • web-javascript • Microsoft Edge 142.0.3595.80

�[32m[✓]�[39m Network resources [819ms]
    �[32m•�[39m All expected network resources are available.

�[33m!�[39m Doctor found issues in 1 category.

Flutter Application Metadata

Type: malformed
Version: 0.0.1
Material: true
Android X: false
Module: false
Plugin: false
Android package: null
iOS bundle identifier: null
Creation channel: null
Creation framework version: null

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P2Important issues not at the top of the work lista: widget previewsIssues related to the Widget Previewer toolingc: crashStack traces logged to the consoler: 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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