Packer: HCL2 filter blocks not working properly in 1.5.6

[lapchynski]

Overview of the Issue

Filter blocks in subnet_filter and source_ami_filter do not behave the same in 1.5.6 as previous versions (I updated from 1.5.4) and do not behave as described in #8889. They also don't behave consistently with each other.

With version 1.5.4 (and 1.5.5), the following works as expected

source "amazon-ebs" "recon-ebs" {
  ...
  subnet_filter {
    filters {
      subnet-id = var.subnet
    }
  ...
  source_ami_filter {
    filters {
      virtualization-type = "hvm"
    }
  ...

With version 1.5.6 the same code as above produces

Error: Unsupported block type

  on recon.pkr.hcl line 80, in source "amazon-ebs" "recon-ebs":
  80:     filters {

Blocks of type "filters" are not expected here. Did you mean "filter"?

Error: Unsupported block type

  on recon.pkr.hcl line 73, in source "amazon-ebs" "recon-ebs":
  73:     filters {

Blocks of type "filters" are not expected here. Did you mean "filter"?

According to #8889, this format should be supported.

Switching to the "filter"-style format below

source "amazon-ebs" "recon-ebs" {
  subnet_filter {
    filter {
      name = "subnet-id"
      value = var.subnet
    }
  ...
  source_ami_filter {
    filter {
      name = "virtualization-type"
      value = "hvm"
    }
  ...

produces the following with version 1.5.6

Error: Unsupported argument

  on recon.pkr.hcl line 82, in source "amazon-ebs" "recon-ebs":
  82:       name = "virtualization-type"

An argument named "name" is not expected here.

and there is no error referring to the filter in the subnet_filter block

Operating system and Environment details

I'm on an x86_64 Ubuntu 18.04 machine running Packer natively and both Packer versions are using the prebuilt binary. (i.e. https://releases.hashicorp.com/packer/1.5.6/packer_1.5.6_darwin_amd64.zip)

[SwampDragons]

Sorry about this -- In v1.5.6 we made a change to be more consistent with terraform where we use the term used by the AWS api itself: in this case, "key" instead of "name". See https://github.com/hashicorp/packer/blob/master/CHANGELOG.md#backwards-incompatibilities-1 for notes on other HCL2 changes.

I'll try to make sure our docs and examples are up to date to reduce confusion.

[lapchynski]

Thank you! I didn't think to look at the changelog but I will do that in the future. Because the conventions vary by API I think documentation for each filter and what convention it uses would be very helpful and reduce confusion.

For anyone else stumbling on this issue, this is what worked for me with 1.5.6 and presumably going forward:

source "amazon-ebs" "recon-ebs" {
  ...
  subnet_filter {
    filter {
      name = "subnet-id"
      value = var.subnet
    }
    ...
  source_ami_filter {
    filter {
      key = "virtualization-type"
      value = "hvm"
    }
    filter {
      key = "name"
      value = "ubuntu/images/*/ubuntu-bionic-18.04-amd64-server-*"
    }
    filter {
      key = "root-device-type"
      value = "ebs"
    }
    ...

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