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 made available through the Packer plugin SDK

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-plugin-sdk/cmd/packer-sdc@latest

• Add //go:generate packer-sdc 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:

  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