How to reference Files with Starlark Function?

[kferrone]

How do I reference a functionFiles from within a Starlark function?

Here is the yaml for my function:
embed.yaml

apiVersion: someteam
kind: Embed
metadata:
  name: test-embed
  annotations:
    config.kubernetes.io/function: |
      starlark:
        path: kustomize/functions/embed/embed.star
spec:
  target:
    kind: Function
    fieldPath: spec.source
    fileRef: cool.py
functionFiles:
- cool.py

Is it even possible for Starlark to reference files from the host? I have a feeling kustomize would have to read files and pass in the content as variables.

Within the code I can only get the name of the files in an array like so:

files = ctx.resource_list["functionConfig"]["functionFiles"]

Now how to actually read the file contents?

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[KnVerey]

To the best of my knowledge, Starlark intentionally cannot do filesystem IO as a feature of the language (not specific to Kustomize). If you're unable to encode the input data into the function config itself, then I suggest you switch to a container function (which supports specified mounts) or an exec function (which has filesystem access inherently).

Please note that we have an open KEP with a proposal for moving plugins in general forward from alpha, and it includes deprecating dedicated starlark support: kubernetes/enhancements#2954. Although Starlark has its advantages, it is a problem for us to maintain and notably causes a permanent inconsistency with kubectl kustomize due to the dependencies it requires. If you feel strongly about it, please comment on the KEP. Assuming the deprecation plan moves forward, we will not be adding features to Kustomize's Starlark function support.

/unassign
/kind feature
/triage unresolved

[kferrone]

I figured it didn't. I wrote normal plugin with python instead. Starlark was an interesting idea, not worried about it at all.