This is a proof of concept illustration of how jsonnet (with the help of yq) can be used as a helm post-renderer (https://helm.sh/docs/topics/advanced/#post-rendering).
-
Clone this repo
-
install yq and jsonnet locally locally, binaries are available in both cases from github release pages: https://github.com/google/jsonnet/releases, https://github.com/mikefarah/yq.
-
Check that all is working:
helm template example --post-renderer ./yj.shYou should see that each k8s object has the labels foo: bar and bar: foo
Then modify the file processors.jsonnet as you wish. Note that in this example each processor is applied to every k8s object in turn.
When consuming third party helm charts you can only modify the resulting k8s objects to the extent that the chart author has anticipated your customisation use case and added a suitable interface. Post renderers allow for arbitrary changes to the k8s objects created from the chart's templates before helm actually applies them to your cluster.