Write hash as JSON inside puppet epp template

I am facing while printing values from .epp template in puppet

1. I have following data in hiera, which defines groups (array of hashes)

profiles::groups:
  - name: 'admins'
    type: 1
    rights: []
  - name: 'users'
    type: 2
    rights: []

2. The above hiera key is called in .epp template like this

   .....    
   groups = <%= require 'json'; JSON.pretty_generate scope['groups'] %> 
   .....

3. Above declaration should print the values in file in following format (from above epp template) but gives error as mentioned below

....... 
groups = [
  {
    "name": "admins",
    "type": 1,
    "rights": []
  },
  {
    "name": "users",
    "type": 2,
    "rights": []
  }
]
.....

Error Message: Error: Could not retrieve catalog from remote server: Error 500 on SERVER: Server Error: Evaluation Error: Error while evaluating a Function Call, epp(): Invalid EPP: Syntax error at 'json' 

While declaring the same format in .erb template works fine and it produces desired output.

In erb it's embedded ruby you can use regular ruby functions, on epp it's embedded Puppet so you need to use Puppet functions. There is a to_json_pretty available in stdlib https://forge.puppet.com/modules/puppetlabs/stdlib which will do the job and you can use it like this;

groups = <%= $groups.to_json_pretty %> 

I've just tested it out with;

# test/manifests/jsontest.pp
class test::jsontest {

  $groups = lookup('test::groups')

  file { '/root/epp':
    ensure  => file,
    content => epp("test/jsondata.epp", {groups => $groups})
  }
}

# test/templates/jsondata.epp
groups = <%= $groups.to_json_pretty %> 

# common.yaml
test::groups:
  - name: 'admins'
    type: 1
    rights: []
  - name: 'users'
    type: 2
    rights: []