How do I set helm values (not files) in ArgoCD Application spec - kubernetes-helm

Question

I looked all over the ArgoCD docs for this but somehow I cannot seem to find an answer. I have an application spec like so:
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
name: myapp
namespace: argocd
spec:
destination:
namespace: default
server: https://kubernetes.default.svc
project: default
source:
helm:
valueFiles:
- my-values.yaml
path: .
repoURL: ssh://git#blah.git
targetRevision: HEAD
However, I also need to specify a particular helm value (like you'd do with --set in the helm command. I see in the ArgoCD web UI that it has a spot for Values, but I have tried every combination of entries I can think of (somekey=somevalue, somekey:somevalue, somekey,somevalue). I also tried editing the manifest directly, but I still get similar errors trying to do so.
The error is long nonsense that ends with error unmarshaling JSON: while decoding JSON: json: cannot unmarshal string into Go value of type map[string]interface {}
What is the correct syntax to set a single value, either through the web UI or the manifest file?

Answer 1

you would use parameters via spec.source.helm.parameters
something like:
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
name: my-app
namespace: argocd
spec:
project: my-project
source:
repoURL: https://charts.my-company.com
targetRevision: "1234"
chart: my-chart
helm:
parameters:
- name: my.helm.key
value: some-val
destination:
name: k8s-dev
namespace: my-ns
Sample from Argo Docs - https://argo-cd.readthedocs.io/en/stable/user-guide/helm/#build-environment

Answer 2

To override just a few arbitrary parameters in the values you indeed can use parameters: as the equivalent of Helm's --set option or fileParameters: instead of --set-file:
...
helm:
# Extra parameters to set (same as setting through values.yaml, but these take precedence)
parameters:
- name: "nginx-ingress.controller.service.annotations.external-dns\\.alpha\\.kubernetes\\.io/hostname"
value: mydomain.example.com
- name: "ingress.annotations.kubernetes\\.io/tls-acme"
value: "true"
forceString: true # ensures that value is treated as a string
# Use the contents of files as parameters (uses Helm's --set-file)
fileParameters:
- name: config
path: files/config.json
But to answer your original question, for the "Values" option in the GUI you pass literal YAML block in the manifest, like:
helm:
# Helm values files for overriding values in the helm chart
# The path is relative to the spec.source.path directory defined above
valueFiles:
- values-prod.yaml
# Values file as block file
values: |
ingress:
enabled: true
path: /
hosts:
- mydomain.example.com
annotations:
kubernetes.io/ingress.class: nginx
kubernetes.io/tls-acme: "true"
labels: {}
Check ArgoCD sample application for more details.