I have an existing project that I want develop into a web app, so I switched to the flutter beta channel. And since I also intend later to refactor my code for null-safety I started upgrading as many package dependencies as are available with null-safe revisions. For now my project has to be a mixed-version program.
I have followed the official Migrating incrementally and Testing or running mixed-version programs instructions but my IDE (IntelliJ) is still riddled with Dart Analysis null-safe errors and my project fails to build because of the same errors. (I have invalidated caches and restarted IntelliJ, to no effect.)
I have set the minimum SDK constraint in pubspec.yaml to 2.12.0-0; I've added // @dart=2.9 to the top of all Dart files I don’t want to consider for null-safe analysis at this point in the migration, including main.dart; and I am using the flutter run --no-sound-null-safety command.
Can someone recommend what can be done to run my project as a mixed-version program?