Transformers

Nixidy supports adding a transformers to Helm releases and Kustomize applications. A transformer is only a function that takes in a list of Kubernetes manifests in attribute sets and returns the same ([AttrSet] -> [AttrSet]). It is called after the manifests have been rendered and parsed into nix but before they're transformed into the nixidy form (<group>.<version>.<kind>.<name>) and can be used to modify the resources.

Transformers can be set globally in nixidy.defaults.helm.transformer for Helm releases and nixidy.defaults.kustomize.transformer for kustomize applications.

Remove Version Specific Labels

It's very common that helm charts will add the labels helm.sh/chart and app.kubernetes.io/version to all resources it renders. This can produce very big diffs when they're updated and nixidy renders them and commits the manifests to a git branch. The changes in these labels are not very relevant and will mostly just be noise to distract from the actual relevant changes of the rendered output.

A transformer can be used to filter out these labels.

{
  applications.argocd.helm.releases.argocd = {
    # ...

    # Remove the following labels from all manifests
    transformer = map (lib.kube.removeLabels [
      "app.kubernetes.io/version"
      "helm.sh/chart"
    ]);
  }
}

Here we use map to call lib.kube.removeLabels on each manifest in the list to remove the specified labels. The example uses function currying, this is equivalent to manifests: map (m: lib.kube.removeLabels ["..."] m) manifests.