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HelmYS - Helm Templating with YS

HelmYS ⧉ is a Kubernetes Helm ⧉ "post renderer" ⧉ that lets you write your Helm chart templates with YS.

YS can be used in combination with Helm's standard Go template ⧉ syntax or it can replace it entirely.

When YS is used exclusively, the Helm chart templates are not only simpler and more concise, but they are also valid YAML files (just like the Chart.yaml and values.yaml files). That means they can be processed with any YAML tools, such as being validated with a YAML linter like yamllint ⧉.

Template File Comparisons🔗

This is a side by side comparison of the Helm chart template YAML files created by helm create <chart-name> and then converted to use YS. The left side is the YS version and the right side is the original Go template version.

ys-chart/templates/helpers.yaml
!YS v0:
defn trunc(s): take(63 s).str(*).replace(/-$/)

# Expand the name of the chart:
chart-name =:
  trunc: Values.nameOverride ||| Chart.name

# Create a default fully qualified app name.
chart-fullname =:
  if Values.fullnameOverride.?:
    trunc: Values.fullnameOverride
    else:
      name =: Values.nameOverride ||| Chart.name
      if name.has?(Release.Name):
        trunc: Release.Name
        format "%s-%s": Release.Name name

# Selector labels:
selectorLabels =::
  app.kubernetes.io/name:: Chart.name
  app.kubernetes.io/instance:: Release.Name

# Chart labels:
chart-labels =::
  helm.sh/chart:: "$(Chart.name)-$(Chart.version)"
  :: selectorLabels
  app.kubernetes.io/version:: Chart.appVersion
  app.kubernetes.io/managed-by:: Release.Service

# Create the name of the service account to use:
serviceAccountName =:
  Values.serviceAccount.name |||:
    if Values.serviceAccount.create:
      chart-fullname
      'default'
go-chart/templates/_helpers.tpl
{{/*
Expand the name of the chart.
*/}}
{{- define "go-chart.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

{{/*
Create a default fully qualified app name.
We truncate at 63 chars because some Kubernetes name fields are limited to
this (by the DNS naming spec).
If release name contains chart name it will be used as a full name.
*/}}
{{- define "go-chart.fullname" -}}
{{- if .Values.fullnameOverride }}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- $name := default .Chart.Name .Values.nameOverride }}
{{- if contains $name .Release.Name }}
{{- .Release.Name | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }}
{{- end }}
{{- end }}
{{- end }}

{{/*
Create chart name and version as used by the chart label.
*/}}
{{- define "go-chart.chart" -}}
{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 |
    trimSuffix "-" }}
{{- end }}

{{/*
Common labels
*/}}
{{- define "go-chart.labels" -}}
helm.sh/chart: {{ include "go-chart.chart" . }}
{{ include "go-chart.selectorLabels" . }}
{{- if .Chart.AppVersion }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
{{- end }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

{{/*
Selector labels
*/}}
{{- define "go-chart.selectorLabels" -}}
app.kubernetes.io/name: {{ include "go-chart.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}

{{/*
Create the name of the service account to use
*/}}
{{- define "go-chart.serviceAccountName" -}}
{{- if .Values.serviceAccount.create }}
{{- default (include "go-chart.fullname" .) .Values.serviceAccount.name }}
{{- else }}
{{- default "default" .Values.serviceAccount.name }}
{{- end }}
{{- end }}
ys-chart/templates/deployment.yaml
!YS v0:
apiVersion: apps/v1
kind: Deployment
metadata:
  name:: chart-fullname
  labels:: chart-labels
spec:
  :when-not Values.autoscaling.enabled.?::
   replicas:: Values.replicaCount
  selector:
    matchLabels:: selectorLabels
  template:
    metadata:
      :when+ Values.podAnnotations.?::
       annotations:: _
      labels:: chart-labels
    spec:
      :when+ Values.imagePullSecrets.?::
       imagePullSecrets:: _
      serviceAccountName:: serviceAccountName
      securityContext:: Values.podSecurityContext
      containers:
      - name:: Chart.name
        securityContext:: Values.securityContext
        image::
          "$(Values.image.repository):\
           $(Values.image.tag ||| Chart.appVersion)"
        imagePullPolicy:: Values.image.pullPolicy
        ports:
        - name: http
          containerPort:: Values.service.port
          protocol: TCP
        livenessProbe:: Values.livenessProbe
        readinessProbe:: Values.readinessProbe
        resources:: Values.resources
        :when+ Values.volumeMounts.?::
         volumeMounts:: _
      :when+ Values.volumes.?::      {volumes:: _}
      :when+ Values.nodeSelector.?:: {nodeSelector:: _}
      :when+ Values.affinity.?::     {affinity:: _}
      :when+ Values.tolerations.?::  {tolerations:: _}
go-chart/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "go-chart.fullname" . }}
  labels:
    {{- include "go-chart.labels" . | nindent 4 }}
spec:
  {{- if not .Values.autoscaling.enabled }}
  replicas: {{ .Values.replicaCount }}
  {{- end }}
  selector:
    matchLabels:
      {{- include "go-chart.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      {{- with .Values.podAnnotations }}
      annotations:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      labels:
        {{- include "go-chart.labels" . | nindent 8 }}
        {{- with .Values.podLabels }}
        {{- toYaml . | nindent 8 }}
        {{- end }}
    spec:
      {{- with .Values.imagePullSecrets }}
      imagePullSecrets:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      serviceAccountName: {{ include "go-chart.serviceAccountName" . }}
      securityContext:
        {{- toYaml .Values.podSecurityContext | nindent 8 }}
      containers:
        - name: {{ .Chart.Name }}
          securityContext:
            {{- toYaml .Values.securityContext | nindent 12 }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag |
                     default .Chart.AppVersion }}"
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          ports:
            - name: http
              containerPort: {{ .Values.service.port }}
              protocol: TCP
          livenessProbe:
            {{- toYaml .Values.livenessProbe | nindent 12 }}
          readinessProbe:
            {{- toYaml .Values.readinessProbe | nindent 12 }}
          resources:
            {{- toYaml .Values.resources | nindent 12 }}
          {{- with .Values.volumeMounts }}
          volumeMounts:
            {{- toYaml . | nindent 12 }}
          {{- end }}
      {{- with .Values.volumes }}
      volumes:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      {{- with .Values.nodeSelector }}
      nodeSelector:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      {{- with .Values.affinity }}
      affinity:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      {{- with .Values.tolerations }}
      tolerations:
        {{- toYaml . | nindent 8 }}
      {{- end }}
ys-chart/templates/serviceaccount.yaml
!YS v0:
:when Values.serviceAccount.create:
  apiVersion: v1
  kind: ServiceAccount
  metadata:
    name:: serviceAccountName
    labels:: chart-labels
    :when+ Values.serviceAccount.annotations.?::
     annotations:: _
  automountServiceAccountToken::
    Values.serviceAccount.automount
go-chart/templates/serviceaccount.yaml
{{- if .Values.serviceAccount.create -}}
apiVersion: v1
kind: ServiceAccount
metadata:
  name: {{ include "go-chart.serviceAccountName" . }}
  labels:
    {{- include "go-chart.labels" . | nindent 4 }}
  {{- with .Values.serviceAccount.annotations }}
  annotations:
    {{- toYaml . | nindent 4 }}
  {{- end }}
automountServiceAccountToken: {{ .Values.serviceAccount.automount }}
{{- end }}
ys-chart/templates/service.yaml
!YS v0:
apiVersion: v1
kind: Service
metadata:
  name:: chart-fullname
  labels:: chart-labels
spec:
  type:: Values.service.type
  ports:
  - port:: Values.service.port
    targetPort: http
    protocol: TCP
    name: http
  selector:: selectorLabels
go-chart/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: {{ include "go-chart.fullname" . }}
  labels:
    {{- include "go-chart.labels" . | nindent 4 }}
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: http
      protocol: TCP
      name: http
  selector:
    {{- include "go-chart.selectorLabels" . | nindent 4 }}