unexpected error using $patch: delete

[ChristopherFry]

What happened?

I see the following error I attempt to build my configuration using kustomize build .:

Error: wrong node kind: expected ScalarNode but got MappingNode: node contents:
$patch: delete

Essentially I am trying to apply two patches to a CRD resource. The first patch sets adds the preserveUnknownFields field to the spec, setting to false, and the second patch removes the creationTimestamp field.

The interesting part is if I reverse the order of the patches in the kustomization.yaml file, the error no longer occurs and I the results I expect.

What did you expect to happen?

No error occurs and I see the resulting yaml.

How can we reproduce it (as minimally and precisely as possible)?

This can be reproduced with the resources created by this script and executing kustomize build . within the newly created kustomize-test directory.

mkdir kustomize-test

cat <<EOF> kustomize-test/kustomization.yaml
resources:
- crd.yaml

patches:
- path: set-preserve-fields.yaml
- path: remove-creation-timestamp.yaml
EOF

cat <<EOF> kustomize-test/skip-suffix.yaml
nameSuffix:
- path: metadata/name
  apiVersion: apps/v1
  kind: Deployment
EOF

cat <<EOF> kustomize-test/crd.yaml
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  creationTimestamp: null
  name: mycrd.domain.dev
spec:
  group: my-group.com
  names:
    kind: MyCRD
    listKind: MyCRDList
    plural: mycrds
    singular: mycrd
  scope: Namespaced
EOF

cat <<EOF> kustomize-test/remove-creation-timestamp.yaml
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: mycrd.domain.dev
  creationTimestamp:
    \$patch: delete
EOF

cat <<EOF> kustomize-test/set-preserve-fields.yaml
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: mycrd.domain.dev
spec:
  preserveUnknownFields: false
EOF

Note with the patches order reversed in the kustomization.yaml file, I am able to get the expected results.

Expected output

> kustomize build .
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: mycrd.domain.dev
spec:
  group: my-group.com
  names:
    kind: MyCRD
    listKind: MyCRDList
    plural: mycrds
    singular: mycrd
  preserveUnknownFields: false
  scope: Namespaced

Actual output

> kustomize build .
Error: wrong node kind: expected ScalarNode but got MappingNode: node contents:
$patch: delete

Kustomize version

v5.0.1

Operating system

MacOS

[cailynse]

I was able to reproduce this bug.

/triage accepted
/priority backlog

[k8s-triage-robot]

This issue has not been updated in over 1 year, and should be re-triaged.

You can:

• Confirm that this issue is still relevant with /triage accepted (org members only)
• Close this issue with /close

For more details on the triage process, see https://www.kubernetes.dev/docs/guide/issue-triage/

/remove-triage accepted

[twelho]

Reproduced as well, Kustomize doesn't seem to be able to delete scalar nodes (fields) with a strategic merge patch.