Helm Chart Rendering (render-helm-chart)#

render-helm-chart is a KRM function in the krm-functions-catalog that renders local or remote Helm charts into Kubernetes manifests. It wraps helm template internally — no separate Helm binary installation is required by the caller 1.

The function integrates with any KRM orchestrator (kpt, kustomize). When used with kpt fn eval, remote charts require --network and local charts require --mount 2.

Chart Resolution: chartHome → Remote Fallback#

The core lookup logic lives in Generate():

1. Local check — chartExistsLocally() checks whether {absChartHome}/{name} is a directory on disk. If the directory exists, the local copy is used and no network call is made.
2. Remote pull — If the chart is not found locally, the function pulls it from the configured repository:
   • Non-OCI repos: pullNonOCIRepo() runs helm repo add then helm pull --untar --untardir {chartHome}.
   • OCI repos (oci:// prefix): pullOCIRepo() optionally runs helm registry login, then helm pull.
3. Template — After the chart is available locally, helm template is executed via templateArgs().

chartHome defaults to tmp/charts when not specified 3. When running inside a container, chartHome must have the tmp/ prefix because the function writes pulled charts to that path 4.

The absolute path used for all operations is resolved once via absChartHome() (filepath.Abs(p.ChartHome)).

FunctionConfig#

Two functionConfig kinds are supported 5:

ConfigMap#

Flat key-value pairs under data. Relevant fields:

6 7

RenderHelmChart (custom resource)#

Supports multiple charts in one function invocation via helmCharts[], plus a helmGlobals block for shared settings like chartHome and configHome 8.

Additional fields available only in RenderHelmChart:

• registry — OCI registry URL for helm registry login 9
• auth — reference to a Secret with data.username / data.password for private repos or registries 10
• valuesInline / valuesMerge — inline values and merge strategy (merge, override [default], replace) 11

Key Source Files#

Examples (from README):

• Local chart example
• Remote chart example
• Kustomize inline values example