feat: enable onExit handlers to access DAG task outputs via workflow.outputs.parameters Fixes #14767

[juanxiu]

onExit handlers can now reference DAG task outputs using {{workflow.outputs.parameters.*}}

• Add global parameter update before onExit handler execution
• Allow workflow.outputs.parameters.* references in validation logic
• Update checkValidWorkflowVariablePrefix, resolveAllVariables, and VerifyResolvedVariables
• Enable onExit handlers to access DAG task outputs without YAML modifications

Fixes #14767

Motivation

In Argo Workflows, the onExit handler cannot access DAG task outputs through workflow.outputs.parameters.*. Due to this limitation, users are unable to implement cleanup or notification logic that depends on the results of DAG task executions.

Modifications

1. Runtime Logic

• Update workflow outputs to global variables before executing the onExit handler

2. Validation Logic

• Ensure that the workflow.outputs.parameters.* pattern is valid across different validation paths

Verification

validation and runtime execution both pass successfully

1. Submission-time Validation Test

• Dry-run (validation only)

./dist/argo submit --dry-run -o yaml --from workflowtemplate/dag-template-exit-outputs -n argo -p namespace=argo

Expected Result: YAML output (validation passes)
Failure Case: failed to resolve {{workflow.outputs.parameters.foo-replicas}} error

2. Runtime Execution Test

• Actual workflow execution

./dist/argo submit --from workflowtemplate/dag-template-exit-outputs -n argo -p namespace=argo

• Wait for workflow completion

kubectl wait --for=condition=completed workflow/[WORKFLOW_NAME] -n argo --timeout=60s

• Check logs

kubectl logs -n argo -l workflows.argoproj.io/workflow=[WORKFLOW_NAME] --tail=10

Expected Result: Exit handler can access: task output
Failure Case: Exit handler can access: (empty value)

Documentation

Example yaml

yaml
apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: data-processing-with-cleanup
spec:
  entrypoint: main
  onExit: cleanup-handler
  templates:
  - name: main
    dag:
      tasks:
      - name: process-data
        template: data-processor
      - name: generate-report
        template: report-generator
        dependencies: [process-data]
  - name: data-processor
    container:
      image: python:3.9
      command: [python, -c]
      args: ["import json; print(json.dumps({'status': 'success', 'records': 1000})) > /tmp/result.json"]
    outputs:
      parameters:
      - name: processing-status
        globalName: data-status
        valueFrom:
          path: /tmp/result.json
  - name: cleanup-handler
    container:
      image: alpine:latest
      command: [sh, -c]
      args: ["echo 'Cleanup completed. Processing status: {{workflow.outputs.parameters.data-status}}'"]