packer-cn/website/content/guides/hcl/component-object-spec.mdx

---
page_title: Generating code for config spec.
sidebar_title: Making a plugin HCL2 enabled
description: Learn how to generate the HCL2 configuration of your component easily.
---

# Auto Generate the HCL2 code of a plugin

From v1.5, Packer can be configured using HCL2. Because Packer has so many
builders, provisioners, and post-processors, we created a on code generation
tool to add the HCL2-enabling code more easily. You can use this code generator
to create the HCL2 spec code of your custom plugin simply. It's a Go binary
package and is located in
[`cmd/mapstructure-to-hcl2`](https://github.com/hashicorp/packer/tree/master/cmd/mapstructure-to-hcl2).

Say you want to configure the `Config` struct of a `Builder` in a package
located in `my/example-plugin/config.go`. Here are some simple steps you can
follow to make it HCL2 enabled:

- run `go install github.com/hashicorp/packer/cmd/mapstructure-to-hcl2`

- Add `//go:generate mapstructure-to-hcl2 -type Config` at the top of
  `config.go`

- run `go generate ./my/example-plugin/...`

  This will generate a `my/example-plugin/config.hcl2spec.go` file containing
  the configuration fields of `Config`.

- Make sure that all the nested structs of `Config` are also auto generated the
  same way.

- Now we only need to make your Builder implement the interface by adding the
  following snippet:

  ```go
  func (b *Builder) ConfigSpec() hcldec.ObjectSpec { return b.config.FlatMapstructure().HCL2Spec() }
  ```

  From now on every time you add or change a field of Config you will need to
  run the `go generate` command again.

A good example of this is the [Config struct of the amazon-ebs builder](https://github.com/hashicorp/packer/blob/master/builder/amazon/ebs/builder.go)