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Even after #169998 lands, I don't know that we want to do this. #169998 only handles newly created Flutter apps. This PR will show that warning for every pre-existing Flutter app.

Perhaps we can try to auto-migrate people AppDelegates and then after some time we can introduce this warning?

I don't think we should try to migrate users in this case. We have a lot of work to do, trying to handle the infinite ways people could be running into this will be a big investment (x2 for swift and objc). I think Apple has shown us a good way forward, provide a warning with a generous grace period, then pull the plug.

I don't think we should try to migrate users in this case. We have a lot of work to do, trying to handle the infinite ways people could be running into this will be a big investment (x2 for swift and objc). I think Apple has shown us a good way forward, provide a warning with a generous grace period, then pull the plug.

I wasn't thinking we'd try to catch every use case - just the basic use case (if the AppDelegate matches the old template exactly, we can safely change it I think). That would get most users (probably?). Then for users who have done custom things to their AppDelegate, they can migrate manually

If you don't handle every case, wouldn't you still want this warning? Can you file an issue for the mechanism that automatically updates app delegates?

If you don't handle every case, wouldn't you still want this warning? Can you file an issue for the mechanism that automatically updates app delegates?

Good point, we would still want the warning - but only after the migration code had landed. I think we should also add more documentation on how to migrate this specific use case. Currently the docs are mostly about platform channels: https://docs.flutter.dev/release/breaking-changes/uiscenedelegate#creating-platform-channels-in-application-didfinishlaunchingwithoptions

Filed #170167