valueFrom not allowed for argument parameters in dag templates (but in steps)

[nice-pink]

Pre-requisites

• I have double-checked my configuration
• I can confirm the issues exists when I tested with :latest
• I'd like to contribute the fix myself (see contributing guide)

What happened/what you expected to happen?

arguments:
  parameters:
  - name: param
    valueFrom:
      configMapKeyRef:
        name: my-config
        key: param

throws the error when submitting in dag template but works for steps.

Error is:

{"code":3,"message":"templates.main.tasks.print missing value for parameter 'param'"}: templates.main.tasks.print missing value for parameter 'param'

Below are the entire workflows.

Version

v3.4.11

Paste a small workflow that reproduces the issue. We must be able to run the workflow; don't enter a workflows that uses private images.

Throws an error:

apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: value-from-fail
spec:
  entrypoint: main
  templates:
  - name: main
    dag:
      tasks:
      - name: print
        template: print-param
        arguments:
          parameters:
          - name: param
            valueFrom:
              configMapKeyRef:
                name: cm-param-test-ping
                key: param

  - name: print-param
    inputs:
      parameters:
      - name: param
    container:
      image: cgr.dev/chainguard/bash:latest
      command:
      - /bin/bash
      - -c
      - |
        set -eu
        echo "{{inputs.parameters.param}}"

Works as expected:

apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: value-from-success
spec:
  entrypoint: main
  templates:
  - name: main
    steps:
    - - name: print
        template: print-param
        arguments:
          parameters:
          - name: param
            valueFrom:
              configMapKeyRef:
                name: cm-param-test-ping
                key: param
  - name: print-param
    inputs:
      parameters:
      - name: param
    container:
      image: cgr.dev/chainguard/bash:latest
      command:
      - /bin/bash
      - -c
      - |
        set -eu
        echo "{{inputs.parameters.param}}"

Config map:

apiVersion: v1
kind: ConfigMap
metadata:
  name: cm-param-test-ping
  labels:
    # Note that this label is required for the informer to detect this ConfigMap.
    workflows.argoproj.io/configmap-type: Parameter
data:
  param: ping

Logs from the workflow controller

kubectl logs -n argo deploy/workflow-controller | grep ${workflow}

Logs from in your workflow's wait container

kubectl logs -n argo -c wait -l workflows.argoproj.io/workflow=${workflow},workflow.argoproj.io/phase!=Succeeded

[nice-pink]

In validate_dab_test.go it looks like the behaviour is intended. I guess to avoid empty parameters. But I think my example from above shows that there are use cases were using valueFrom instead of value makes sense.

Or is there a reason, I don't see, why this works with steps but not with dag?