Re-using UUID in helm configmap - kubernetes

Question

There's a similar question that alludes to the possibility of auto-generating a uuid in helm charts when used as a secret or configmap. I'm trying precisely to do that, but I'm getting a new uuid each time.
My test case:
---
{{- $config := (lookup "v1" "ConfigMap" .Release.Namespace "{{ .Release.Name }}-testcase") -}}
apiVersion: v1
kind: ConfigMap
metadata:
name: "{{ .Release.Name }}-testcase"
namespace: "{{ .Release.Namespace }}"
labels:
app.kubernetes.io/managed-by: "{{ .Release.Service }}"
app.kubernetes.io/instance: "{{ .Release.Name }}"
app.kubernetes.io/version: "{{ .Chart.AppVersion }}"
helm.sh/chart: "{{ .Chart.Name }}-{{ .Chart.Version }}"
data:
{{- if $config }}
TEST_VALUE: {{ $config.data.TEST_VALUE | quote }}
{{- else }}
TEST_VALUE: {{ uuidv4 | quote }}
{{ end }}
I initially deploy this with:
helm upgrade --install --namespace test mytest .
If I run it again, or run with helm diff upgrade --namespace test mytest . I get a new value for TEST_VALUE. When I dump the contents of $config it's an empty map {}.
I'm using Helm v3.9.0, kubectl 1.24, and kube server is 1.22.
NOTE: I couldn't ask in a comment thread on the other post because I don't have enough reputation.

Answer 1

Refering to my issue where you enclosed your stack overflow post : https://github.com/helm/helm/issues/11187
A way to make your configmap work is to save as a variable before conditionnaly set your value. This means every time you upgrade, you'll generate a UUID which will normally will not be used, but this is not dramatic.
When assigning an existing value, := should become =.
Also don't forget to b64enc your value in your manifest
{{- $config := uuidv4 | b64enc | quote -}}
{{- $config_lookup := (lookup "v1" "ConfigMap" .Release.Namespace "{{ .Release.Name }}-testcase") -}}
{{- if $config_lookup -}}
{{- $config = $config_lookup.data.TEST_VALUE -}}
---
apiVersion: v1
kind: ConfigMap
metadata:
name: "{{ .Release.Name }}-testcase"
namespace: "{{ .Release.Namespace }}"
labels:
app.kubernetes.io/managed-by: "{{ .Release.Service }}"
app.kubernetes.io/instance: "{{ .Release.Name }}"
app.kubernetes.io/version: "{{ .Chart.AppVersion }}"
helm.sh/chart: "{{ .Chart.Name }}-{{ .Chart.Version }}"
data:
TEST_VALUE: {{ $config | quote }}