Getting results of a step in a nested WorkflowTemplate structure

[Zujiry]

My problem is, that I need the output.parameter to use it in the input of the next step in a precise-template.

I have three different templates:

• default-template
• specific-templates (2)
  • defining one step
• precise-template
  • Defining many steps

In this structure, the specific-template uses the default-template. The precise-template uses many specific-templates. Looking like this:

default-template

apiVersion: argoproj.io/v1alpha1
kind: ClusterWorkflowTemplate
metadata:
  name: output-default-wft
spec:
  templates:
  - name: run-task-output-first
    inputs:
      parameters:
      - name: download_url
    script:
      image: python:3.10
      command: [python]
      source: |
        import json
        from pathlib import Path
        print("download_url: ", {{inputs.parameters.download_url}})
        result = {{inputs.parameters.download_url}}
        # Write the result to the output file
        Path("/tmp").mkdir(exist_ok=True)
        Path("/tmp/result.json").write_text(
            json.dumps({"download_url": result[0]})
        )
    outputs:
      parameters:
      - name: result
        valueFrom:
          path: /tmp/result.json
  - name: run-task-output-last
    inputs:
      parameters:
      - name: execution_environment
    container:
      image: python:3.10
      command: [python]
      args: ["-c", "print(str({{inputs.parameters.execution_environment}}))"]

specific-template-first:

apiVersion: argoproj.io/v1alpha1
kind: ClusterWorkflowTemplate
metadata:
  name: output-first-wft
spec:
  templates:
  - name: run-task-wft
    inputs:
      parameters:
      - name: download_url
    steps:
    - - name: step-first
        templateRef: 
          name: output-default-wft
          template: run-task-output-first
          clusterScope: true
        arguments:
          parameters:
          - name: download_url
            value: "{{inputs.parameters.download_url}}"

specific-template-last

apiVersion: argoproj.io/v1alpha1
kind: ClusterWorkflowTemplate
metadata:
  name: output-last-wft
spec:
  templates:
  - name: run-task-wft
    inputs:
      parameters:
      - name: download_url
    steps:
    - - name: step-end
        templateRef: 
          name: output-default-wft
          template: run-task-output-last
          clusterScope: true
        arguments:
          parameters:
          - name: execution_environment
            value: |
              {
                "context": { 
                  "download_url": "{{inputs.parameters.download_url}}"
                }
              }

precise-template using the specific-templates:

apiVersion: argoproj.io/v1alpha1
kind: ClusterWorkflowTemplate
metadata:
  name: output-wft
spec:
  templates:
  - name: output
    inputs:
      parameters:
      - name: download_url
    steps:
    - - name: first
        templateRef:
          name: output-first-wft
          template: run-task-wft
          clusterScope: true
        arguments:
          parameters:
          - name: download_url
            value: "{{inputs.parameters.download_url}}"
    - - name: last
        templateRef:
          name: output-last-wft
          template: run-task-wft
          clusterScope: true
        arguments:
          parameters:
          - name: download_url
            value: "{{=jsonpath(steps['step-first'].outputs.parameters.result, '$.download_url')}}"

Here the error appears, because the download_url is given as "{{=jsonpath(steps['step-first'].outputs.parameters.result, '$.download_url')}}" and not evaluated -> as is the case if the precise-template directly uses the default-template without the extra step definition in the specific-templates.
The problem is, that I need the specific-templates to be executable themselves but also be usable in steps of other WorkflowTemplates.

By the way: The structure works, only the result access is not correct.

The workflow:

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: output-wf-
spec:
  entrypoint: output
  arguments:
    parameters:
    - name: download_url
      value: |
        [
          "file:///test_image"
        ]
  workflowTemplateRef:
    name: output-wft
    clusterScope: true 

[Zujiry]

After trial and error: You can actually solve this, via the propagation of outputs.

Adapting the specific-template-first like this:

apiVersion: argoproj.io/v1alpha1
kind: ClusterWorkflowTemplate
metadata:
  name: output-first-wft
spec:
  templates:
  - name: run-task-wft
    inputs:
      parameters:
      - name: download_url
    steps:
    - - name: step-first
        templateRef: 
          name: output-default-wft
          template: run-task-output-first
          clusterScope: true
        arguments:
          parameters:
          - name: download_url
            value: "{{inputs.parameters.download_url}}"
  outputs:
    parameters:
    - name: task_result
      valueFrom:
        parameter: "{{steps.step-first.outputs.parameters.result}}"

You can access the parameter task_result in the precise-template

    - - name: last
        templateRef:
          name: output-last-wft
          template: run-task-wft
          clusterScope: true
        arguments:
          parameters:
          - name: download_url
            value: "{{=jsonpath(steps['step-first'].outputs.parameters.task_result, '$.download_url')}}"