Crossplane Composition Kustomize Bug

This repo is intended to demonstrate a bug in Crossplane's Composition object when attempting to patch array items with Kustomize. (Map patches work as expected)

It appears the Composition CRD does not define correct merge keys for all array/list types.

Repo Structure

The crossplane and k8s directories have a simple kustomize base and overlays directory structure. Each overlays directory has an array and map directory

The overlays/array directories attempt to patch an array item and the overlays/map directories attempt to patch a map.

To Reproduce Bug

Clone this repo and cd into crossplane-composition-object directory and run kustomize command.

git clone <link>
cd crossplane-composition-object
kubectl kustomize overlays/array

Instead of appending the tag to the resources array item at base.spec.forProvider.tags.kustomize, the entire resources array item is replaced by the patch. All other fields are brought in from crossplane-composition-object/base/composition.yaml as expected.

# result of 'kubectl kustomize overlays/array'
---
apiVersion: apiextensions.crossplane.io/v1
kind: Composition
metadata:
  labels:
    crossplane.io/xrd: xpostgresqlinstances.database.example.or
    provider: gcp
  name: example
spec:
  compositeTypeRef:
    apiVersion: database.example.org/v1alpha1
    kind: XPostgreSQLInstance
  patchSets:
  - name: metadata
    patches:
    - fromFieldPath: metadata.labels[some-important-label]
      type: FromCompositeFieldPat
  resources:
  - name: cloudsqlinstance # <------------------- array item being patched
    base:
      spec:
        forProvider:
          tags:
            kustomize: patching 'resources' array item replaces entire item
    
  writeConnectionSecretsToNamespace: crossplane-system

The map patch in crossplane-composition-object/overlays/map works as expected.

kubectl kustomize overlays/map

For Reference

The k8s deployment object array and map patches both work as expected and are included as working example references.

Specifically, the array patch appends the field it is patching to the array item, instead of replacing the array item like in the crossplane composition example above.

cd ..
cd k8s-deployment-object
kubectl kustomize overlays/array
kubectl kustomize overlays/map