How to parametrise volumes with @script() ?

[EricBoix]

I'm trying to convert some fully functional in house AW source to Hera.
The interesting AW feature boils down to "parametrizing" the mountPath of a volume with a template input value, which goes

  - name: do-some-stuff-template
    inputs:
      parameters:
      - name: persistedVolume
    script:
      image: python:3.9-alpine
      source: |
        <snip ... some python code ...snip>
      volumeMounts:
        - name: workdir
          mountPath: "{{inputs.parameters.persistedVolume}}"          # What is the Hera equivalent ?

After taking some inspiration from Hera's "script auto infer" example (and some dark magic incantations, since I have to admit that I the underlying inference mechanism totally eludes me) I dared trying the following:

@script(
    image="python:3.9-alpine",
    volume=Volume(
        name="workdir",
        mount_path=persisted_volume,             # How to transmit this argument (at build time) ?
    ),
)
def do_some_stuff(persisted_volume):          # NameError: name persisted_volume is not defined
     <snip ... some python code ...snip>

Alas this fails (not enough chicken blood spilled?).
The question is thus: how does one pass over parameters to a @scrip() configuration section in Hera ?

[elliotgunton]

Unfortunately right now the easiest way to do this is a mix of Argo syntax and the inputs present in the script decorator (we're working on improving this!)

@script(
    image="python:3.9-alpine",
    inputs=[Parameter(name="persistedVolume")],  # specify an input to the template here instead of as a function arg
    volume=Volume(
        name="workdir",
        mount_path="{{inputs.parameters.persistedVolume}}",  # refer to the input with Argo syntax
    ),
)
def do_some_stuff():          #  persisted_volume (probably) not needed here
     <snip ... some python code ...snip>

[EricBoix]

Thank you @elliotgunton . Except for the typo (the trailing third curly bracket, }, within the mount_path definition mount_path="{{inputs.parameters.persistedVolume}}}" must be removed) this mix Argo syntax does indeed the trick.
Closing discussion.

[elliotgunton]

Oops! Thank you, edited in case people come back to the issue.

[EricBoix]

@elliotgunton Also I wanted to mention (at least with version 5.6.0) that it seems that the calling prototype seems to require the mention of the argument. That is one has to write

def do_some_stuff(persisted_volume):          #  persisted_volume MUST be mentioned here 
                                              # (although it is only used in the `@script()` section)

Otherwise one gets a failed to resolve {{inputs.parameters.claim_name}} at hera submission stage.
But please don't take my words on this since my mileage is really low on this (less than an hour fooling around in a messed up context).

Here is a full example for you to quickly experiment

from hera.workflows import DAG, Parameter, script, Workflow


@script(
    image="{{inputs.parameters.image}}",
)
def test():  # FAILS at submission stage with message:  
             #     failed to resolve {{inputs.parameters.image}}`
             # but the following definitions smoothly accepts submission
             # def test(image):
    ...


with Workflow(generate_name="fail-", entrypoint="main") as w:
    with DAG(name="main"):
        t1 = test(
            arguments=Parameter(
                name="image",
                value="pyton;3.9-alpine",
            ),
        )
w.create()

Thanks again.