Code review comment for lp://qastaging/~renatofilho/ubuntu-system-settings-online-accounts/update-account-removal-message

> The third-party apps should not store the contacts,calendar,messages on
> application local database. They should use The contact, organizer,
> telepathy/messaging, sync service implement plugins.

Right now they can't, because of bug 1227821 and bug 1227824 (unless those bug reports are inaccurate, in which case we have a security problem).

By the time those functions are provided, depending on how many apps exist, it would take time for them to migrate to the "right" way of doing things.

And even if they do migrate, you don't know whether they have or not. A brand-new app in 2018 could still do things the old way, copying data directly from Google, because Online Accounts still gives it direct access to the Google Account.

> With that we can make sure that if the account is deleted all data is deleted
> together.

As long as you are only saying "should not", rather than "can't possibly", you aren't making sure.