I currently have a schema in production (cloudKit and local files) containing non-optional transformable values, e.g.
@Attribute(.transformable(by: TestTransformer.self))
var number: TestTransformable = TestTransformable.init(value: 100)
Unfortunately, this is preventing any migration from succeeding (documented at length in FB22151570).
Briefly summarized, any migration from a Schema containing non-optional transformable values fails between willMigrate and didMigrate with the error "Can't find model for source store". This occurs for all migrations, including lightweight with a migration plan, lightweight without a plan, and custom migrations. Worst of all, this also prevents migration to optional transformable values, or the elimination of the transformable value entirely, leaving us completely stuck.
(note: optional transformable values only work when they have a default value set to nil, otherwise even these have issues migrating)
We already have features being blocked by this issue, and would like to preserve user-data while restoring our ability to move forwards with database.
Are there any known workarounds for using SwiftData (+CloudKit) when schema migration is non-operational?