GRDB 7: Async database accesses honor Task cancellation

[groue]

In GRDB 6, asynchronous database accesses such as try await read { ... } or try await write { ... } complete even if the wrapper Task is cancelled.

In GRDB 7, asynchronous database accesses respect Task cancellation. If a Task is cancelled, reads and writes throw a CancellationError, pending transactions are rolled back, and the database is not modified. The only SQL statement that can execute in a cancelled database access is ROLLBACK.

The effect of this change on your application depends on how it uses tasks. For example, take care of database jobs initiated frop the task SwiftUI modifier.

If you want an asynchronous database access to always complete, regardless of Task cancellation, wrap it in an unstructured Task:

// Create a new Task in order to ignore
// cancellation of the current task, and
// make sure database changes are always
// committed to disk.
let task = Task {
    try await writer.write { ... }
}
// If needed, wait for the database job to complete:
try await task.value

Other asynchronous database accesses, such as methods accepting a completion blocks (asyncRead, etc.), Combine publishers, RxSwift observables, do not handle cancellation and will proceed to completion by default.