Intent to Deprecate HCLv1

[schmichael]

Nomad adopted HCLv2 for Jobspecs in 2020. HCLv2 is not strictly backward compatible with HCLv1, so we have maintained the HCLv1 jobspec parser behind the nomad job run -hcl1 ... flag, the job parse HCLv1 field, and the jobspec Go package.

Deprecation Plan

The time has come to deprecate HCLv1.

• After Nomad 1.8.0 no new jobspsec fields will be added to the jobspec package.
• In Nomad 1.9.0 all hclv1 support will be removed.

TODO

• Add deprecation warning to CLI in Nomad 1.8.0 jobspec: add deprecation warnings for removal of HCLv1 #23913
• Add deprecation comments to jobspec package in Nomad 1.8.0 jobspec: add deprecation warnings for removal of HCLv1 #23913
• Add deprecation notes to docs: https://developer.hashicorp.com/nomad/docs/release-notes/nomad/upcoming#nomad-1-9-0
• Create a PR for total removal in Nomad 1.9.0 jobspec: remove HCL1 support #23912

Resources

• Original HCLv2 issue: Jobspec HCLv2 Support #7220

[42wim]

Hi, I'm wondering if there will be a solution for the heredoc issue before hcl1 gets removed ?

• Allow disabling hcl2 interpolation for string literals #10777
• Template Stanza single quote and HCL2 cause parser error #9838

[tgross]

Yeah we'll certainly need to do that.

[tgross]

Wanted to follow up on this after my investigations in #9838. There's no way for us to do this without direct support in HCL. Adding support for this was previously rejected by the core HCL maintainer team, but even if we got past that (probably possible) it's a lot of work at the very "bottom" of the HCL stack, and we don't have the resources to do this work currently. Given that there's a workaround for this already (either manually escaping in the template.data or using template.source), we're not going to block HCL1 removal for heredoc support.