tfgen

Generate Terraform configuration from Go.

tfgen is a small library for building Terraform JSON configuration programmatically in Go. You describe your infrastructure with plain Go values and tfgen emits *.tf.json that any Terraform-compatible CLI (Terraform or OpenTofu) can apply.

Unlike Hashicorp's now unsupported CDKTF, configuration is entirely flexible and does not depend on generating strong types based off provider versions. This means you can reliably and quickly generate Terraform-compatible JSON using easy to understand Go.

Keep a small generator in your project and wire it to go generate:

package main

//go:generate go run .

import (
	"log"
	"os"

	"github.com/ably/tfgen"
)

func main() {
	stack := tfgen.NewStack("example")

	bucket := &tfgen.Resource{
		Type: "aws_s3_bucket",
		Name: "example",
		Config: tfgen.Config{
			"bucket": "my-example-bucket",
		},
	}
	stack.AddResource(bucket)

	// Ref builds a Terraform interpolation referencing an attribute of the
	// resource, so you never hand-write "${...}" strings.
	stack.AddOutput(&tfgen.Output{
		Name:  "bucket_arn",
		Value: bucket.Ref("arn"),
	})

	f, err := os.Create("main.tf.json")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	if err := stack.Write(f); err != nil {
		log.Fatal(err)
	}
}

Run go generate ./... to write main.tf.json, ready to apply with terraform or tofu:

{
  "output": {
    "bucket_arn": {
      "value": "${aws_s3_bucket.example.arn}"
    }
  },
  "resource": {
    "aws_s3_bucket": {
      "example": {
        "bucket": "my-example-bucket"
      }
    }
  }
}

See examples/generate for a complete, runnable example.

A Stack is one Terraform configuration. You add building blocks to it, a Resource, Data source, Module, Provider, Output, Variable, or the terraform block, then serialise it to JSON. Config is a map[string]any, so any attribute maps directly onto Terraform's JSON syntax, and helpers such as Resource.Ref and Variable.Ref build interpolation references so you never hand-write "${...}" strings.

Write a single stack to any io.Writer with Stack.Write, or write a set of stacks to their conventional files at {baseDir}/stacks/{name}/main.tf.json with Stacks.Write. See the Go documentation for the full API.

The providers/* subpackages provide optional, typed constructors for common providers. They are thin sugar over tfgen types, so you can always drop down to a plain tfgen.Provider or tfgen.Resource.

• providers/aws — AWS provider
• providers/cloudflare — Cloudflare provider
• providers/ably — the Ably Terraform provider: apps, API keys, namespaces, and queues

Contributions are welcome, see CONTRIBUTING.md.

Licensed under the Apache License 2.0.