https://github.com/ansible/ansible/issues/8633 test case on a role with only library modules

hosts

# /hosts
localhost ansible_connection=local

module

#!/usr/bin/python
# /roles/modules/library/module
from ansible.module_utils.basic import *
AnsibleModule({}).exit_json(**{})

site.yml

# /site.yml
---
- hosts: all
  gather_facts: false
  roles: [modules]
  tasks: [{module:}]