Handle delete before adding finalizer

In Reconcile() method, move the object deletion above add finalizer.
Finalizers can't be set when an object is being deleted.

Signed-off-by: Sunny <darkowlzz@protonmail.com>

internal/controller/kustomization_controller.go

@@ -196,18 +196,20 @@ func (r *KustomizationReconciler) Reconcile(ctx context.Context, req ctrl.Reques
 		}
 	}()
 
+	// Prune managed resources if the object is under deletion.
+	if !obj.ObjectMeta.DeletionTimestamp.IsZero() {
+		return r.finalize(ctx, obj)
+	}
+
 	// Add finalizer first if it doesn't exist to avoid the race condition
 	// between init and delete.
+	// Note: Finalizers in general can only be added when the deletionTimestamp
+	// is not set.
 	if !controllerutil.ContainsFinalizer(obj, kustomizev1.KustomizationFinalizer) {
 		controllerutil.AddFinalizer(obj, kustomizev1.KustomizationFinalizer)
 		return ctrl.Result{Requeue: true}, nil
 	}
 
-	// Prune managed resources if the object is under deletion.
-	if !obj.ObjectMeta.DeletionTimestamp.IsZero() {
-		return r.finalize(ctx, obj)
-	}
-
 	// Skip reconciliation if the object is suspended.
 	if obj.Spec.Suspend {
 		log.Info("Reconciliation is suspended for this object")