Kustomize/Kubernetes - Nested envFrom injection - kubernetes

Question

I'm trying to add envs injection based on envFrom
A simplified structure looks something like that:
├── base
│   ├ ─ backend
│   ├── backend.properties
│   ├── app1
│   │   ├── app1_backend.properties
├ ── deployment.yaml
│   │   ├── ingress.yaml
│   │   ├── kustomization.yaml
├── common.properties
├── frontend
│   ├── app1
│ ├── app1_frontend.properties
│   │   ├── deployment.yaml
│   │   ├── ingress.yaml
│   │   ├── kustomization.yaml
│   │   └── service.yaml
│   ├── frontend.properties
│   └── kustomization.yaml
└── kustomization.yaml
I would like to generate properties on the main level(common), backend/frontend level, and particular app level.
So I was trying to add the following patch on main level and it works:
- op: add
path: /spec/template/spec/containers/0/envFrom
value:
- configMapRef:
name: common-properties
and following code to nested directories(backend/frontend/particular app)
- op: add
path: "/spec/template/spec/containers/0/envFrom/-"
value:
configMapRef:
name: backend-properties
But it doesn't work with the following error:
add operation does not apply: doc is missing path: "/spec/template/spec/containers/0/envFrom/-": missing value
I have seen some examples on GitHub where that syntax was used: https://github.com/search?l=YAML&p=1&q=%2Fspec%2Ftemplate%2Fspec%2Fcontainers%2F0%2FenvFrom%2F-&type=Code (you have to be logged in to see results) And I'm not sure this stopped work on specific Kustomize version(I'm using the newest version - 4.5.3) or it never worked
I have already written some Kustomize patches and syntax with /- to resources usually worked fine to resources that already exist on the manifest.
It's possible to inject that envFrom on different levels?

Answer 1

It's hard to diagnose your problem without a reproducible example, but if I start with this Deployment:
apiVersion: apps/v1
kind: Deployment
metadata:
name: example
spec:
replicas: 1
selector:
matchLabels:
app: example
template:
spec:
containers:
- name: example
image: docker.io/alpine:latest
envFrom:
- configMapRef:
name: example-config
And use this kustomization.yaml, which includes your patch without
changes:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- deployment.yaml
patches:
- target:
kind: Deployment
name: example
patch: |-
- op: add
path: "/spec/template/spec/containers/0/envFrom/-"
value:
configMapRef:
name: backend-properties
Then everything seems to work and I get the resulting output from
kustomize build:
apiVersion: apps/v1
kind: Deployment
metadata:
name: example
spec:
replicas: 1
selector:
matchLabels:
app: example
template:
spec:
containers:
- envFrom:
- configMapRef:
name: example-config
- configMapRef:
name: backend-properties
image: docker.io/alpine:latest
name: example