[BUG] Component finalizers intermittently disappear

[cbarbian-sap]

Describe the bug
Components (that is, instances of components.core.cs.sap.com) which are themselves dependents of another component sometimes lose their finalizers. To be precise, from time to time, the component-operator finalizer (component-operator.cs.sap.com) vanishes from the dependent component, and after a little while it is added back.

Tested with Version
component-operator: v0.1.26
component-operator-runtime: v0.3.84

To Reproduce
Create a component A which contains another component B, and watch B; after a while its finalizer will disappear, and then, after another little time, be added back.

Expected behavior
Finalizer should be always there, instead of being flickering.

[cbarbian-sap]

After some analysis, it turns out that this is because of the reclaiming logic of certain field managers. When the object is reconciled for the first time, the finalizer is added through an update (PUT) call, and ownership is recorded as such in the managed fields (operation: Update). At the next reconcile (triggered because of some change or because of fore-reapply), that managed field entry is claimed here by the main manager entry (operation: Apply); this happens because of and only in the case of equality of the field managers of the containing and the managed component. Since the intended manifest does not contain any finalizer (but now claim that field) it is cleared; with the next reconcile it is then added back by the main reconcile loop. And so on.