I have a Core Data app on the App Store that places its persistent store in the default location within the Application Support directory. At some point, I add widgets to the app while utilizing SwiftData. I create a widget extension and the app group to link both targets. I migrate my persistent store from the default location to the app group container directory. Now, the SwiftData code pointing to the shared container in the widget extension can query data. Here's the sample project for illustration up to this point.
Then, I decided to get rid of the Core Data code entirely. Move everything in the main target to SwiftData. I need to keep my persistence controller object, however, because I can never assume that the entirety of my user base has migrated. I do need to ditch the Core Data model file. Otherwise, my new SwiftData models would conflict with the auto-generated ones from that file. But once I do that, my migration code breaks. I can't set up a persistent container without the model. And I need the container for migration. SwiftData has no native interface to migrate the store to a new location. There is a line in the documentation stating that the framework copies the store to an app group container automatically. But I wasn't able to verify that claim.