Unable to use user variable in vagrantfile_template with HCL2 packerfile

[ghost]

This issue was originally opened by @aacebedo as hashicorp/packer#10828. It was migrated here as a result of the Packer plugin split. The original body of the issue is below.

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Overview of the Issue

I am generating a vagrantfile when creating a box with packer. In this vagrantfile, I use variables defined in the packer file.
In the vagrantfile.tpl I add tags like {{ user myvariable }}. When I use a JSON packer file, everything is ok.
I upgraded my packer json file into the HCL2 format and the syntax seems to have changed for those variables as they are not replaced anymore. I may be missing something here but the document "engine" page of the JSON section does not exist in the HCL section.

Reproduction Steps

• Create a HCL2 packer file using the vagrant post-processor
• In the vagrant post-processor define a vagranfile_template file
• In the vagrantfile template refers to user defined variables coming from the packer file using the {{ user myvariable }} syntax.
• Run packer build, the variables are not changed.

Packer version

1.7.0

Simplified Packer Buildfile

file.pkr.hcl
[...]
  locals {
   mylocal = "helloworld"
  }
  post-processor "vagrant" {
    keep_input_artifact = true
    vagrantfile_template = ./vagrantfile.tpl
  }
[...]

file vagrantfile.tpl
[...]
something = {{ user `mylocal` }}
[...]

Operating system and Environment details

Linux x86_64

Log Fragments and crash.log files

N/A