Replacement filter documentation for array creation

[lack]

Describe the bug

Using a replacement filter with the create option set to true, one can create an arbitrarily deep map to the point where the target value is set. However, the tool cannot create arrays or append to arrays.

Files that can reproduce the issue

kustomization.yaml

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - resources.yaml
replacements:
- source:
    kind: Pod
    name: pod
    fieldPath: spec.containers.0.image
  targets:
  - select:
      name: deploy1
    fieldPaths:
    - spec.template.spec.containers.0.image
    options:
      create: true

resources.yaml

apiVersion: v1
kind: Pod
metadata:
  name: pod
spec:
  containers:
  - image: busybox
    name: myapp-container
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy1

Expected output

apiVersion: v1
kind: Pod
metadata:
  name: pod
spec:
  containers:
  - image: busybox
    name: myapp-container
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy1
spec:
  template:
    spec:
      containers:
      - image: busybox

Actual output

Error: wrong Node Kind for spec.template.spec.containers expected: SequenceNode was MappingNode: value: {{}}

Kustomize version

Built from master branch

git describe:

kustomize/v4.5.2-25-gf67dd5bbb

Platform

Linux

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[lack]

Did some further digging. Turns out if the intermediate array is specified with a lookup value like .[name=foo]., the intermediate array is created just fine, and with the lookup value added to the intermediate map.

Using a numerical index like .0., wildcard .*., or hyphen .-. are not allowed for intermediate creation.

[lack]

So maybe this is more of a doc bug? If the docs on the replacements filter had better examples of complex creation, I'd be happy.

For example:

• create a field with an intermediate array entry:

foo.bar.[key=value].intermediate.leaf

foo:
  bar:
  - key: value
    intermediate:
      leaf: scalarSourceValue

• append a scalar to an array

foo.bar.[=placeholder]

foo:
  bar:
  - scalarSourceValue

• append a copied structure to an array

foo.bar.[=placeholder]

foo:
  bar:
  - sourceKey1: value1
    sourceKey2: value2

• create a new single field structure in an array

foo.bar.[newkey=].newkey

foo:
  bar:
  - newkey: scalarSourceValue

[KnVerey]

Thank you for all the examples. Let's mark this as a documentation issue for now, and if a use case comes up where targeting by index is required, we can reconsider supporting that specifically.

/kind documentation /rename Replacement filter documentation for array creation

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/lifecycle stale

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/lifecycle rotten

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/lifecycle stale

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/lifecycle rotten

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/close not-planned

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@k8s-triage-robot: Closing this issue, marking it as "Not Planned".

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The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

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/close not-planned

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