Cannot read packages spec

[nan-yu]

What happened?

The .dart_tool/package_config.json file is missing when running the dartpad frontend code from the main branch.
However, I'm still able to run the app even with the error.

Note: The error is gone when switching to the gen-ai branch.

Steps to reproduce problem

1. Check out the main branch.
2. Run dart pub get to generate the package configuration file.
3. Run the dartpad frontend: flutter run -d chrome --web-port 8888 --web-browser-flag "--disable-web-security".

Additional info

Dart

Dart version:

$ dart --version
Dart SDK version: 3.7.0 (stable) (Wed Feb 5 04:53:58 2025 -0800) on "macos_arm64"

Error:

$ flutter run -d chrome --web-browser-flag "--disable-web-security"
Resolving dependencies in `/usr/local/google/home/nanyu/projects/dart-pad`... (1.5s)
Downloading packages... 
  async 2.12.0 (2.13.0 available)
  fake_async 1.3.2 (1.3.3 available)
  leak_tracker 10.0.8 (10.0.9 available)
  material_color_utilities 0.11.1 (0.12.0 available)
  pointycastle 3.9.1 (4.0.0 available)
  vm_service 14.3.1 (15.0.0 available)
Got dependencies in `/usr/local/google/home/nanyu/projects/dart-pad`!
6 packages have newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.
Launching lib/main.dart on Chrome in debug mode...
Waiting for connection from debug service on Chrome...             63.1s
DartUri: Cannot read packages spec: file:///usr/local/google/home/nanyu/projects/dart-pad/pkgs/dartpad_ui/.dart_tool/package_config.jsonError: PathNotFoundException: Cannot open file,
path = '/usr/local/google/home/nanyu/projects/dart-pad/pkgs/dartpad_ui/.dart_tool/package_config.json' (OS Error: No such file or directory, errno = 2)
This app is linked to the debug service: ws://127.0.0.1:37189/lIAEuWp3gn4=/ws
Debug service listening on ws://127.0.0.1:37189/lIAEuWp3gn4=/ws