how to use jsonpath in when condition

[liuzqt]

apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: my-pipeline
spec:
  entrypoint: main
  arguments:
    parameters: 
      - name: myjson
         value: '{"key1": 100}'
  templates:
    - name: main
      dag:
        tasks:
          - name: dummy
            when: "1 < {{jsonpath(workflow.parameters.myjson), '$.key1')}}"
            inline:
              container:
                image: docker/whalesay:latest
                command: [sh, -c]
                args: ["echo {{workflow.parameters.myjson}}"]

I was trying to access the json value in when condition using

when: "1 < {{jsonpath(workflow.parameters.myjson), '$.key1')}}"

but got this error:

Invalid 'when' expression '1 < {{jsonpath(workflow.parameters.myjson), '$.key1')}}': Invalid token: '{{' (hint: try wrapping the affected expression in quotes ("))

[thegreymatter]

I believe you are missing = to mark it as an expression and not a template

when: "1 < {{jsonpath(workflow.parameters.myjson), '$.key1')}}"

should turn to

when: "1 < {{=jsonpath(workflow.parameters.myjson), '$.key1')}}"

[liuzqt]

tried that, but no luck, got another error:

Invalid 'when' expression '1 < {{=jsonpath(workflow.parameters.myjson), '$.key1')}}': Invalid token: '{{=' (hint: try wrapping the affected expression in quotes ("))

reproducing template:

apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: my-pipeline
spec:
  entrypoint: main
  arguments:
    parameters: 
      - name: myjson
        value: '{"key1": 100}'
  templates:
    - name: main
      dag:
        tasks:
          - name: dummy
            when: "1 < {{=jsonpath(workflow.parameters.myjson), '$.key1')}}"
            inline:
              container:
                image: docker/whalesay:latest
                command: [sh, -c]
                args: ["echo {{workflow.parameters.myjson}}"]

[thegreymatter]

whitespace is required after {{=

[liuzqt]

Hi @thegreymatter I've tried adding whitespace but still not working

when: "1 < {{= jsonpath(workflow.parameters.myjson), '$.key1')}}"

and the error msg is the same

Invalid 'when' expression '1 < {{= jsonpath(workflow.parameters.myjson), '$.key1')}}': Invalid token: '{{=' (hint: try wrapping the affected expression in quotes ("))

Am I doing something wrong?

[agilgur5]

As the below comment says, your jsonpath has an extra closing parenthesis. Fixing that makes it work:

when: "1 < {{=jsonpath(workflow.parameters.myjson, '$.key1')}}"

[alexec]

when conditions do not support {{=, you cannot do this I'm afraid

[liuzqt]

@alexec thanks. Is there any workaround to evaluate json object from workflow parameters in when condition?

[alexec]

AFAIK no

[liuzqt]

got it, thanks

[crenshaw-dev]

Just abuse a bug to make it work.

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  name: my-pipeline
spec:
  entrypoint: main
  arguments:
    parameters:
      - name: myjson
        value: '{"key1": 100}'
  templates:
    - name: main
      dag:
        tasks:
          - name: dummy
            when: "1 < {{=jsonpath(workflow.parameters.myjson, '$.key1')}}"
            inline:
              container:
                image: docker/whalesay:latest
                command: [sh, -c]
                args: ["echo {{workflow.parameters.myjson}}"]

 $ argo submit -n argo test.yaml --log
Name:                my-pipeline
Namespace:           argo
ServiceAccount:      default
Status:              Pending
Created:             Wed Mar 02 12:15:17 -0500 (now)
Progress:            
Parameters:          
  myjson:            {"key1": 100}

This workflow does not have security context set. You can run your workflow pods more securely by setting it.
Learn more at https://argoproj.github.io/argo-workflows/workflow-pod-security-context/

The part of Argo Workflows that shouts at you for using expressions in when fields only sees the {{= if there's an error in the expression (and it therefore doesn't get replaced with some other value). If you fix the typo (the extra ) after workflow.parameters.myjson), the expression evaluates to true before the shouty code sees it.

It's a bit like drinking your Coca-Cola before going through airport security. You're moving the same stuff, but now it's allowed.

(I can't think of a good metaphor for the expression failing to execute... you try to drink the Coke, but the lid is too tight? idk. Anyway, you gotta drink the Coke, or you're not getting through security.)