KnativeServing - config - features - kubernetes.podspec-persistent-volume-claim/write - but no support for subPathExpr

Describe the feature

While activating the features kubernetes.podspec-persistent-volume-claim & kubernetes.podspec-persistent-volume-write allow servicing of pod using persistent volume claim (write mode with isolation subPath attribute), we noticed the usage of the subPathExpr is not allowed.

This silent filtering occurs CRD side + hook validation. I'm told using any dynamic elements to be bad practice in knative developpment, we should allow this fine grained control when required.

I'm currently facing a situation where agnostic, fieldref attributes are required to access specific directory inside a shared pvc.

Would be great to have either ; the subPathExpr policy allowed / not filtered out (while requisting kubernetes.podspec-persistent-volume-claim for instance) OR a new feature, kubernetes.podspec-persistent-volume-claim-subPathExpr like for the sake.

thanks for your feedback,

Kr,

D

Start by tracing how the kubernetes.podspec-persistent-volume-claim feature is represented in the CRD and how hook validation filters subPathExpr. Compare the existing feature policy with the proposed dedicated subPathExpr feature, then confirm the chosen behavior allows the required field without weakening unrelated validation.