rudder

Rudder is a simple Helm chart rendering machine that helps you uncover bugs with rendered charts before applying them to Kubernetes.

Features

• Render Helm charts against a values file and post the result as a PR comment
• Extract nested values from YAML files using dot-notation selectors
• Automatic PR comments with rendered output when running in pull request context
• Collapsible output for easy review of values and rendered manifests

Usage as GitHub Action

Basic Example

- uses: AndreasMoerch/rudder@main
  with:
    values-file: 'path/to/values.yaml'
    chart-path: 'path/to/chart'
  env:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

Full Workflow Example

name: Render Helm Chart on PR

on:
  pull_request:
    types: [opened, synchronize, reopened]

permissions:
  contents: read
  pull-requests: write

jobs:
  render-helm:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Install Helm
        uses: azure/setup-helm@v4
        with:
          version: 'latest'

      - name: Render Helm chart
        uses: AndreasMoerch/rudder@main
        with:
          values-file: 'example/values.yaml'
          values-selector: 'spec.source.helm.valuesObject'
          chart-path: 'example/chart'
          release-name: 'my-release'
          namespace: 'default'
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

Inputs

Input	Required	Default	Description
values-file	No	-	Path to the YAML values file. If omitted, the chart's own values.yaml is used
values-selector	No	-	Dot-notation path to extract nested values (e.g., spec.source.helm.valuesObject)
chart-path	Yes	-	Path to the Helm chart directory
release-name	No	release	Release name for Helm template rendering
namespace	No	-	Kubernetes namespace for template rendering

Outputs

Output	Description
rendered-yaml	The rendered Helm chart YAML output
extracted-values	The values extracted from the values file

Environment Variables

Variable	Required	Description
GITHUB_TOKEN	Yes (for PR comments)	Provided automatically by GitHub Actions

PR Comments

When running in a pull request context, Rudder automatically posts a comment with:

• The values used for rendering (collapsible)
• The full rendered chart output (collapsible)

If rendering fails, the error is posted as a PR comment so it is visible without digging into the GHA logs.

Development

This is a TypeScript-based GitHub Action.

Setup

npm install

Build

npm run build

Run locally

# Use example defaults
node dist/index.js

# With a custom values file
node dist/index.js --values-file example/values.yaml --chart-path example/chart

# All options
node dist/index.js --values-file example/values.yaml --values-selector spec.helm.values --chart-path example/chart --release-name my-release --namespace default