Deletion of nil/empty fields in K8S resources

[bianchi2]

I noticed that when an object has been created with a field set, for example, values in ArgoCD application, and then values are removed from the object, the resulting ArgoCD app still keeps values, though other changes like helm chart version get propagated.

It looks like this holds true to any field that was initially set but then removed. Is there a way to change that?

[swermin]

We have the same issue on our map-fields. Fields that are removed are being kept anyway.
For example, ConfigMap data keys are not being deleted when updating the desired resource.

Based on this data table from kubernetes, https://kubernetes.io/docs/tasks/manage-kubernetes-objects/declarative-config/#merging-changes-to-map-fields, it should delete the field when the last applied configuration has the key, but the desired doesn't. The only reason why the merge would happen is if the key in the ConfigMap is missing from both the desired state and from the last applied coniguration annotation.
We verified this by running tests with kubectl apply -f test.yaml.

What we found is that, the crossplane kubernetes provider, changes the last applied configuration annotation before calling client.Apply which seems to mess with kubernetes own internal logic. For reference, this is the function we looked at:

provider-kubernetes/internal/controller/cluster/object/syncer.go

Line 52 in 06f8258

func (p *PatchingResourceSyncer) SyncResource(ctx context.Context, obj *v1alpha2.Object, desired *unstructured.Unstructured) (*unstructured.Unstructured, error) {