consider enabling templated variables in import paths

[blancharda]

Overview

When working with skeleton package imports, the same import path can be listed many times in a single config:

 - name: set-zarf-vars
    required: true
    import:
      name: set-zarf-vars
      url: oci://ghcr.io/defenseunicorns/packages/dubbd-rke2:0.10.1-skeleton

  - name: preflight
    required: true
    import:
      name: preflight
      url: oci://ghcr.io/defenseunicorns/packages/dubbd-rke2:0.10.1-skeleton

  - name: load-certs
    required: true
    import:
      name: load-certs
      url: oci://ghcr.io/defenseunicorns/packages/dubbd-rke2:0.10.1-skeleton
  ...

The "problem" is exacerbated in packages with many components. The replication leaves room for error and goes against typical DRY code/configuration practices. Tools like Renovate can help lower the burden of updating with CI automation, but for local development and testing it can still be a chore.

Proposed solution

Ideally, the version number or the full OCI path could be replaced with a variable so that it could easily be changed throughout the config or even passed in at build time:

constants:
  - name: DUBBD_OCI
    value: "oci://ghcr.io/defenseunicorns/packages/dubbd-rke2:0.10.1-skeleton"

components:
  - name: set-zarf-vars
    required: true
    import:
      name: set-zarf-vars
      url: "###ZARF_PKG_TMPL_DUBBD_OCI###"
  
  - name: preflight
    required: true
    import:
      name: preflight
      url: "###ZARF_PKG_TMPL_DUBBD_OCI###"

  - name: load-certs
    required: true
    import:
      name: load-certs
      url: "###ZARF_PKG_TMPL_DUBBD_OCI###"
  ...

Currently variable templating does not support variables in import paths.

Workaround

We are currently working around the issue using YAML anchors (thanks @Noxsios!), but it should be noted that this violates the zarf yaml schema which will cause trouble with linting:

x-dubbd-oci: &dubbd_version "oci://ghcr.io/defenseunicorns/packages/dubbd-rke2:0.14.0-skeleton"

components:
  - name: set-zarf-vars
    required: true
    import:
      name: set-zarf-vars
      url: *dubbd_version
  ...

[AustinAbro321]

Assuming we make this change we also have to change zarf prepare lint to no longer warn that url: "###ZARF_PKG_TMPL_DUBBD_OCI###" won't be evaluated

[Noxsios]

This can safely be closed now that x- is allowed in zarf.yaml's schema.

Simple usages of YAML anchors like this is a well supported and documented feature of the YAML spec.