Transform a helm dict into a list - kubernetes-helm

Question

I'm using a Helm chart to control what environment variables are set for a certain container in a deployment.
In my Values.yaml, I have an entry called env which is a dictionary:
image:
repository: xxxx.yyyyy.com/myimage
pullPolicy: IfNotPresent
# Enviroment variables that will be passed to the container.
env: {}
Now, I'll pass variables to the env dict using --set:
helm upgrade mydeployment chart --set env.VARIABLE=test
However, this must be transformed into a list to adhere to Kubernetes yaml:
spec:
template:
spec:
containers:
- name: {{ .Chart.Name }}
image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
imagePullPolicy: {{ .Values.image.pullPolicy }}
# This should come from that dict
env:
- name: VARIABLE
value: "test"
I don't know how to use the template language from Helm (sprig / go) to achieve that. Is it even possible?

Answer 1

To iterate through the map, the core Go text/template language provides a range keyword that can iterate through maps or arrays.
{{ range $key, $value := .Values.env }}
...
{{ end }}
Inside of this you can put arbitrary text. Helm doesn't require this to be any particular kind of YAML construct, just so long as the final result is valid YAML. For this setup a typical loop would look like
env:
{{- range $key, $value := .Values.env }}
- name: {{ quote $key }}
value: {{ quote $value }}
{{- end }}
You do need to be careful with indentation here. As a rule of thumb it often will work to include a - "swallow whitespace" indicator inside the open {{ and to not include one inside the close }}. The - name: must be at least as indented as the env: above it (ignoring the range line), and value: must be aligned with name:. I might put all of the template-language lines (the range and end) starting at the first column, even if they're embedded in a structure that's nested more.
spec:
template:
spec:
containers:
- name: {{ template "chart.fullname" . }}
env:
{{- range $key, $value := .Values.env }}
- name: {{ quote $key }}
value: {{ quote $value }}
{{- end }}
image: {{ .Values.registry }}/{{ .Values.image }}:{{ .Values.tag }}