Argo Workflow: "Bad Request: json: cannot unmarshal string into Go struct field" - unmarshalling

Question

I have a Argo WorkflowTemplate that looks like this:
apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
name: test-container-command
spec:
entrypoint: main
templates:
- name: main
inputs:
parameters:
- name: command
container:
image: alpine:latest
command: "{{ inputs.parameters.command }}"
env: # some predefined env
What I want to do is to create a WorkflowTemplate that can execute an arbitrary command specified by the input parameter command. That way, users of this WorkflowTemplate can supply the parameter command with an array of strings and then execute it like:
apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
generateName: test-run-
spec:
workflowTemplateRef:
name: test-container-command
entrypoint: main
arguments:
parameters:
- name: command
value:
- echo
- hello
However, when I try to save this WorkflowTemplate, the Argo server gave me this error message:
Bad Request: json: cannot unmarshal string into Go struct field Container.workflow.spec.templates.container.command of type []string
It seems that Argo expects the field .spec.templates.container.command to be an array of strings, but it treat "{{ inputs.parameters.command }}" as a string, even though I'm trying to supply the parameter command with an array of strings.
Is there any way to achieve what I was trying to do as the WorkflowTemplate test-container-command, i.e. provide a WorkflowTemplate for the user to execute arbitrary commands with a predefined container and env?

Answer 1

As it says in error command should be list of strings.
You need to reformat your template to:
container:
image: alpine:latest
command: ["{{ inputs.parameters.command }}"]
Now argo should create your workflow without any problems
You could also use
container:
image: alpine:latest
command:
- "{{ inputs.parameters.command }}"
Edit
As you want to run some commands within the image it would be much better instead of container use script template
apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
name: test-container-command
spec:
entrypoint: main
templates:
- name: main
inputs:
parameters:
- name: command
- name: extraEnv
script:
image: alpine:latest
command: [ "sh" ]
env:
- { name: ENV1, value: "foo" }
- { name: ENV2, value: "{{ inputs.parameters.extraEnv }}" }
source: |
{{ inputs.parameters.command }}