"packer validate" validates HCL file as JSON if not suffixed with 'pkr.hcl'

[deepbrook]

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Overview of the Issue

Running the validate command against my HCL file does not validate the file as expected after https://github.com/hashicorp/packer/pull/9346 was merged and released with 1.6.0, if the template's suffix is not .pkr.hcl.

Reproduction Steps

Vaidating a template named template.hcl with packer validate throws the following:

❯ packer validate --syntax-only resource/package/template.hcl
Failed to parse template: Error parsing JSON: invalid character 'v' looking for beginning of value
At line 1, column 1 (offset 1):
    1: v
      ^

Renaming the file to template.pkr.hcl solves the issue.

Packer version

❯ packer --version
1.6.0

Operating system and Environment details

Ubuntu 18.04

[deepbrook]

Oh right. Renaming the template to template.pkr.hcl works as expected. That's picky. Updated the issue accordingly.

[azr]

Hey @deepbrook, thanks for opening. Yup, that's the behaviour, because the schema/layout of an HCL file is tool dependant -- the schema for a Terraform file != the schema for a Packer file -- Packer HCL2 ignores non *.pkr.hcl files because it does not and will not know about other schemas from other tools. Because it might be a Terraform file, a Nomad file or something else Packer is 'blind to it'.

Currently the default main maintained format is the JSON format and because no HCL file is found, this falls back to reading files with the JSON parser, which will open anything.

Note that in the (most likely far) future when the current JSON layout is going to be deprecated; Packer is still going to be blind to files that are not suffixed with *.pkr.hcl.

This has a lot of benefits, like allowing developer tools to differentiate between a TF files and a PKR file; which will make the ecosystem better etc. etc.

Cheers !

[deepbrook]

This has a lot of benefits, like allowing developer tools to differentiate between a TF files and a PKR file; which will make the ecosystem better etc. etc.

i'd expect the tool to just eat the file and validate it, but I'm also not a big fan of hand-holding. Additionally, wouldn't it make more sense to have a hashbang-esque header line in the file to declare the tool the file is used for? But I was also under the impression that HCL is tool agnostic, so never you mind me. I'm sure you've had plenty of discussions on this. :) Thanks for the quick reply.

[azr]

Sure no worries, :D yes HCL2 is tool specific ! That's why it's so nice because you can bend it to your will a bit more, read things a bit later with a context, etc. But then coming from JSON it can be a bit confusing.

[ghost]

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