Plugin Helm

Plugin Purpose

Transform kustomize YAML → Helm chart for operator distribution.

Default: Reads dist/install.yaml, writes to dist/chart/ Flags: --manifests=<input> and/or --output-dir=<output>

Development Workflow

After code changes in pkg/plugins/optional/helm/v2alpha/:

1. make install - Build and install updated binary
2. make generate-charts - Regenerate all sample charts in testdata
3. make verify-helm - Run yamllint + helm lint + kube-linter
4. Test installation in real cluster if changing generation logic

Never commit without running make verify-helm.

Values.yaml Rules

Comment Syntax (Strict)

• ## = Documentation/description
• # = Commented-out spec value
• Always blank ## line between description and spec

## Description of the field
##
# fieldName: value

Uncomment Policy

Uncomment a value only if:

1. Extracted from kustomize - The value exists in the source manifests
2. Standard Helm convention - Common fields users expect uncommented (replicas, image, resource names)

Keep commented if:

1. Optional Kubernetes feature - Not currently used in the operator (imagePullSecrets, priorityClassName)
2. Advanced configuration - Not needed for basic usage (topology spread, pod disruption budget)
3. User customization fields - Name overrides, custom labels that users should explicitly set

Template Conditional Pattern (Critical)

All values.yaml fields MUST be conditional in templates. If a user removes a field from values.yaml, the chart must still work.

Required patterns:

Use {{- with }} for optional blocks:

{{- with .Values.manager.affinity }}
affinity: {{ toYaml . | nindent 10 }}
{{- end }}

Use {{- if }} with fallback for required fields:

resources:
  {{- if .Values.manager.resources }}
  {{- toYaml .Values.manager.resources | nindent 10 }}
  {{- else }}
  {}
  {{- end }}

Never: Direct value reference without conditionals

# WRONG - breaks if removed from values.yaml
affinity: {{ toYaml .Values.manager.affinity | nindent 10 }}

When to use | default vs conditionals:

• Do NOT use | default for fields extracted from kustomize - they are always present in values.yaml
• NEVER use | default for fields that can be legitimately set to 0 (e.g., replicas for scale-to-zero). Helm treats 0 as falsy and will use the default instead, breaking the intended behavior.
• For optional K8s fields that have built-in defaults (e.g., imagePullPolicy), use {{- with }} conditionals to let K8s apply its own defaults when not specified:

  {{- with .Values.manager.image.pullPolicy }}
  imagePullPolicy: {{ . }}
  {{- end }}
  

• Core fields like replicas, image.repository are always extracted from kustomize - use direct references:

  replicas: {{ .Values.manager.replicas }}
  image: "{{ .Values.manager.image.repository }}..."
  

When adding new values.yaml fields, always add conditionals in templates.

Comment Content Rules (values.yaml)

1. One to two lines max - Be concise
2. Focus on user action - What they can configure, not how it works internally
3. Include examples - Show correct YAML structure for commented values
4. Use plain English - Follow Kubernetes Documentation Style Guide
5. End with blank ## line

Good:

## Container image pull secrets for private registries
##
# imagePullSecrets:
#   - name: regcred

Bad:

# This field is used by the template engine to render imagePullSecrets
# into the deployment spec when the value is provided by the user
# imagePullSecrets: []

Code Style

Go Code Comments

• Be concise - Explain WHY, not WHAT (code should be self-documenting)
• No unnecessary comments - Well-named functions/variables > comments
• Plain text only - No arrows, emojis, or decorative symbols
• Follow Go conventions - See Effective Go

Good:

// TemplatePorts replaces port numbers with Helm template references.
// Uses suffix matching to avoid false positives when project name contains "webhook".
func TemplatePorts(yamlContent string, resource *unstructured.Unstructured) string {

Bad:

// This function processes the yaml content and templates the ports
// by checking if it's a webhook or metrics service and then using
// regular expressions to replace the port numbers with values
func TemplatePorts(yamlContent string, resource *unstructured.Unstructured) string {

Code Generation Logic

The plugin uses two different Machinery approaches:

Dynamic Templates (from kustomize)

Location: pkg/plugins/optional/helm/v2alpha/scaffolds/internal/kustomize/

All Kubernetes resources from dist/install.yaml are converted using the templater:

• Parses kustomize YAML → Applies Helm templating → Outputs to templates/
• Uses DynamicTemplate wrapper (pre-rendered content, not Go templates)
• Always overwrites (IfExistsAction = OverwriteFile)
• Examples: manager/manager.yaml, rbac/*.yaml, webhook/*.yaml

Key file: dynamic_template.go - Wraps pre-rendered templates for Machinery

Boilerplate Templates (fixed files)

Location: pkg/plugins/optional/helm/v2alpha/scaffolds/internal/templates/

Static chart files use standard Machinery Go templates:

• Chart.yaml - Never overwrites (IfExistsAction = SkipFile)
• values.yaml, NOTES.txt, _helpers.tpl, .helmignore - Respect --force flag
• Generated from Go templates, not kustomize output

Important: Never delete the templates/ directory. Let Machinery overwrite files in place.

Values.yaml Generation

When modifying what appears in values.yaml:

1. Check Extraction struct for available extracted data
2. Use conditionals to only render if value exists
3. Maintain comment/uncomment logic based on rules above
4. Test with multiple project types (with/without webhooks, metrics, etc.)
5. Follow Kubernetes Documentation Style Guide for all user-facing comments

Critical Design Decisions

CRD Placement: templates/crd/ not crds/

Decision: CRDs are placed in templates/crd/ instead of the standard crds/ directory.

Rationale: Helm's crds/ directory never upgrades CRDs on helm upgrade. For Kubernetes operators, CRD updates are critical (new API fields, validation changes). Placing CRDs in templates/crd/ ensures they upgrade with the chart.

Trade-off: Cannot mix CRDs and Custom Resources in the same chart (Helm installation order limitation).

Action: Preserve this placement. Do not move CRDs to crds/ directory.

File Preservation

The plugin uses Kubebuilder's Machinery framework for file management:

Never overwrite: Chart.yaml (user-managed version info)

Overwrite only with --force: values.yaml, NOTES.txt, _helpers.tpl, .helmignore, .github/workflows/test-chart.yml

Always overwrite: All templates/ resources (manager, rbac, webhook, etc.)

Important: Use Machinery's IfExistsAction to control overwrite behavior. Never delete the templates/ directory or individual files - let Machinery overwrite them in place. This preserves file timestamps and avoids breaking user workflows (e.g., open editors, file watchers).

Documentation Updates

Plugin documentation must stay synchronized with code changes.

When modifying plugin behavior:

1. Update docs/book/src/plugins/available/helm-v2-alpha.md to reflect changes
2. Follow Kubebuilder tutorial-based documentation style:
   • Be concise
   • Example-driven with code snippets showing actual usage
   • Clear section structure: What - Why/When - Usage - Examples (if required)
3. Follow Kubernetes Documentation Style Guide
4. Add specific error scenarios only for known, reproducible errors with fixes

Common Tasks

Adding a New values.yaml Field

1. Check if value exists in Extraction struct
2. Add extraction logic in the extractor
3. Add rendering logic in values generation
4. Follow comment rules above
5. Add conditional usage in template (use {{- with }} or {{- if }} - see Template Conditional Pattern)
6. Run make install && make generate-charts && make verify-helm

Changing Chart Structure

1. Modify chart scaffolder orchestration
2. Update template generators if needed
3. Regenerate all samples with make generate-charts
4. Update plugin documentation if user-visible

Fixing Template Generation

1. Locate template in the templates directory
2. Modify template logic
3. Test with make install and run plugin on test project
4. Run make generate-charts to update all samples
5. Check diffs carefully - ensure no unintended changes
6. Run make verify-helm

Testing

Test Structure (Ginkgo/Gomega BDD)

All tests use Ginkgo v2 + Gomega for behavior-driven development:

var _ = Describe("Feature Name", func() {
    Context("Scenario description", func() {
        It("should do specific behavior", func() {
            // Arrange, Act, Assert
            Expect(result).To(Equal(expected))
        })
    })
})

• Unit tests (*_test.go): Fast, isolated component tests
• Integration tests (//go:build integration): End-to-end chart generation

Running Tests

# Unit tests only (fast)
make test-unit

# Integration tests (requires kubebuilder binary in PATH)
make test-integration

# Helm chart validation (yamllint, helm lint, kube-linter)
make verify-helm

Test Coverage Requirements

When adding features, ensure tests cover:

1. Extraction scenarios: Does it extract the new field from kustomize YAML?
2. Generation scenarios: Does it render correctly in values.yaml?
3. Template scenarios: Does the template handle missing/present values?
4. Edge cases:
   • Field present vs absent in kustomize
   • Field removed from values.yaml by user
   • Different data types (string, int, bool, map, array)
   • Empty values vs nil vs not present

BDD pattern example:

Describe("Webhook port extraction", func() {
    Context("when webhook is present in kustomize", func() {
        It("should extract port and add to values.yaml", func() { ... })
        It("should use port conditionally in template", func() { ... })
    })

    Context("when webhook is not present", func() {
        It("should not add webhook section to values.yaml", func() { ... })
        It("should not render webhook port in template", func() { ... })
    })

    Context("when user removes webhook from values.yaml", func() {
        It("should not break template rendering", func() { ... })
    })
})

Testing Checklist

Before submitting PR:

• make test-unit passes
• make test-integration passes
• make install succeeds
• make generate-charts succeeds
• make verify-helm passes
• Test chart installation (at minimum):
  • cd testdata/project-v4-with-plugins && make helm-deploy IMG=test:latest
• Test scenarios not covered by default testdata:
  • Create mock test projects for edge cases your change affects
  • Examples: projects without webhooks, without metrics, without cert-manager, cluster-scoped RBAC, multi-namespace RBAC
  • Run plugin on mock projects and verify chart generation
  • Install generated charts on test cluster
• Check generated values.yaml follows comment rules (syntax, uncomment/comment logic)
• Verify templates use conditionals ({{- with }} or {{- if }}) for all values
• Test with custom --manifests and --output-dir flags
• New features have unit + integration tests with BDD scenarios
• Tests cover extraction, generation, and template rendering
• Tests cover edge cases (field present/absent/removed)

References

See references/REFERENCE.md for:

• Documentation links
• Helm best practices
• Kubernetes operator resources
• Sample chart locations

Source: kubernetes-sigs/kubebuilder — distributed by TomeVault.