How to access hiera data from ERB template?

[akomakom]

Describe the Bug

Puppet Documentation suggests that it is possible to access variables from module ERB templates via the scope['variable_name'] syntax. It is unclear whether that only works for module variables, eg:

class module_name {
    $var1 = 3 # This works
}

or also for hiera-defined variables, eg in module_name/data/common.yaml:

module_name::var1: 3 # This does not work

Expected Behavior

This ERB template should work:

This is a value: <%= scope['module_name::var1']%>

Steps to Reproduce

Steps to reproduce the behavior:

Create a puppet module with the following files:

• module_name/templates/test.erb

This is a value: <%= scope['module_name::var1']%>

• module_name/hiera.yaml

---
version: 5

defaults:
  datadir: data
  data_hash: yaml_data

hierarchy:
  - name: "common"
    path: "common.yaml"

• module_name/data/common.yaml:

This is a value: <%= scope['module_name::var1']%>

• module_name/manifests/init.pp:

   file { '/some/test':
     content => template("$module_name/test.erb")
   }

Environment

• Version Puppetserver 8.7.0
• Platform Redhat 9

Additional Context

I have tried scope['var1'], scope.lookupvar( <full and short name>0, etc.
I can only resolve the value in a template if it is defined as an explicit variable in the manifest, eg:
$var1 = $module_name::var1

[joshcooper]

It's possible to call the lookup function from within an ERB template, see https://www.puppet.com/docs/puppet/7/lang_template_erb.html#puppet_functions_templates