harness-parser

A small Go utility and package for rendering Harness-style Go templates using one or more YAML values files.

It supports:

• Rendering a single template file
• Rendering a directory of Kubernetes manifest templates
• Layering multiple values files (later files override earlier files)
• Optional interpolation of Harness placeholders for local testing
• Helpful template error output with file and line context

Requirements

• Go 1.26+

Quick Start

Build the CLI:

make build

Run with the included examples:

./bin/harness-parser example-template.yaml example-values.yaml

Install CLI

Install into your GOPATH/bin:

make install

Then run from anywhere (if GOPATH/bin is on your PATH):

harness-parser example-template.yaml example-values.yaml

CLI Usage

harness-parser [flags] <template-or-directory> [values-file ...]

• <template-or-directory>: required path to a template file or directory
• [values-file ...]: optional one or more values YAML files, or a single values directory
• Default values file: example-values.yaml

Flags:

• -env <name>: in values directory mode, select only values for the given env
• -interpolate-secrets: resolve Harness placeholders from values and fake secrets
• -secrets-file <path>: explicitly provide a fake secrets YAML file

When multiple values files are provided, they are merged in argument order. Later files override earlier files.

If a single values directory is provided, values files are auto-discovered (top-level only):

• values.yaml first
• then values-*.yaml / values-*.yml in lexical order
• secrets.yaml and *.secrets.yaml are excluded from value layering

With -env <name> and values directory mode, selected files are:

• values.yaml (always required)
• values-<env>.yaml (if present)
• values-<env>-*.yaml / values-<env>-*.yml in lexical order

Example:

harness-parser ./templates ./values -env prod

Single File Example

harness-parser ./templates/deployment.yaml ./test/values.yaml

Directory Example

harness-parser ./templates ./test/values.yaml

Templates Directory + Values Directory

harness-parser ./templates ./values

Layered Values Example

harness-parser ./templates/deployment.yaml ./values/base.yaml ./values/stage.yaml ./values/az1.yaml

Local Interpolation Example

harness-parser -interpolate-secrets ./templates ./values/values.yaml ./values/values-stage.yaml ./values/values-stage-az1.yaml

With -interpolate-secrets, if -secrets-file is not provided, the parser auto-discovers adjacent files:

• <values-basename>.secrets.yaml
• secrets.yaml

Example fake secrets file:

team/path/db-password: fake-db-password
db-password: fake-db-password
pipeline.variables.tag: test-tag
service.name: encryption-service-test

Directory mode behavior:

• Top-level files only (non-recursive)
• Only .yaml and .yml files are considered
• File must contain both apiVersion: and kind: to be treated as a Kubernetes manifest
• Matching files are rendered in sorted filename order
• Processing continues when one file fails; failures are summarized at the end

Strict Mode Behavior

Strict mode is enabled automatically when you pass custom values files.

Strict mode checks values for unresolved Harness expressions like <+...> and fails if any are found. If -interpolate-secrets is enabled, interpolation runs before strict validation.

Make Targets

make help

Common targets:

• make build - build CLI into bin/harness-parser
• make install - copy CLI into GOPATH/bin
• make run TEMPLATE=<path> VALUES=<file> - run parser with make variables
• make deps - tidy dependencies
• make clean - remove build output

Using as a Go Package

package main

import (
  "fmt"

  harnessparser "harness-parser"
)

func main() {
  out, err := harnessparser.RenderFile("./templates/deployment.yaml", "./values.yaml")
  if err != nil {
    panic(err)
  }

  fmt.Println(out)
}

Or with layered values:

package main

import (
  "fmt"

  harnessparser "harness-parser"
)

func main() {
  out, err := harnessparser.RenderFileMulti(
    "./templates/deployment.yaml",
    []string{"./values/base.yaml", "./values/stage.yaml", "./values/az1.yaml"},
  )
  if err != nil {
    panic(err)
  }

  fmt.Println(out)
}

Example Files

• example-template.yaml
• example-values.yaml

Use these as a starting point for your own templates and values files.