crd-helm-wrapper

CRD Helm Wrapper

A Go tool that wraps Kubernetes CRD YAML files with Helm template conditionals for:

• Feature flags (crds.install.server, crds.install.registry, crds.install.virtualMcp)
• Resource policy annotations (crds.keep → helm.sh/resource-policy: keep)

Why This Tool?

Helm does not upgrade CRDs during helm upgrade operations. CRDs placed in the crds/ directory are only processed during initial installation. By placing CRDs in templates/ with conditionals, they are upgraded alongside the chart.

Raw CRDs generated by controller-gen don't have Helm templating. This tool wraps them with conditionals so users can:

• Enable/disable specific CRD groups via feature flags
• Prevent Helm from deleting CRDs on uninstall

Usage

# Run the tool
go run main.go \
  -source ../files/crds \
  -target ../templates \
  -verbose

Flags

Feature Flag Groups

CRDs are grouped by feature flags. Some CRDs belong to multiple groups:

Output Format

For single-flag CRDs:

{{- if .Values.crds.install.server }}
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  annotations:
    {{- if .Values.crds.keep }}
    helm.sh/resource-policy: keep
    {{- end }}
    controller-gen.kubebuilder.io/version: v0.17.3
  name: mcpservers.toolhive.stacklok.dev
spec:
  ...
{{- end }}

For shared CRDs (multiple groups):

{{- if or .Values.crds.install.server .Values.crds.install.virtualMcp }}
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  annotations:
    {{- if .Values.crds.keep }}
    helm.sh/resource-policy: keep
    {{- end }}
    controller-gen.kubebuilder.io/version: v0.17.3
  name: mcpexternalauthconfigs.toolhive.stacklok.dev
spec:
  ...
{{- end }}

Values Configuration

The wrapped CRDs expect these values:

crds:
  # Whether to add the "helm.sh/resource-policy: keep" annotation
  keep: true
  # Feature flags for CRD groups
  install:
    server: true
    registry: true
    virtualMcp: true

Template Escaping

CRD descriptions may contain Go template-like syntax (e.g., {{.steps.step_id.output}}). The tool automatically escapes these to prevent Helm from interpreting them as template directives.

Template Files

The tool uses embedded template files in the templates/ directory:

Adding New CRD Groups

To add a new feature flag group, update the crdFeatureFlags map in main.go:

var crdFeatureFlags = map[string][]string{
    "newcrdtype": {"newFeature"},
    // For shared CRDs:
    "sharedcrd": {"server", "newFeature"},
}

Then add the corresponding value to values.yaml.