kyverno/test/conformance/chainsaw/validate/e2e/old-object-exists/policy.yaml

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: check-old-object
spec:
  background: false
  rules:
    - name: require-labels
      match:
        all:
          - resources:
              operations:
                - CREATE
                - UPDATE
              kinds:
                - Namespace
      validate:
        failureAction: Enforce
        message: "The label `size` is required"
        pattern:
          metadata:
            labels:
              size: "small | medium | large"
    - name: check-old-object
      match:
        all:
          - resources:
              operations:
                - UPDATE
              kinds:
                - Namespace
      validate:
        failureAction: Enforce
        message: "request.oldObject cannot be null for update requests"
        deny:
          conditions:
            all:
              - key: "{{ request.oldObject.metadata == null }}"
                operator: Equals
                value: true