The current version of angular components doesn't work on Dart 12.14.x. It actually causes Web Dev to hang. See: dart-lang/webdev#1415 (comment)
This is down to Dart 12.14 requiring a version the analyzer package which is only supported by Angular 7.0.0 which the current version of Angular Components doesn't support.
Are there plans for this project to support Angular 7.0.0?