Use lookup/dynamic variable names in Ansible jinja2 template

Question

The playbook below should generate a file with the content:

a,b
ssh_host_key
ssh_rsa_host_key

However, the way I construct the variable names results in either syntax/templating errors or 'variable name does not exists':

---
- hosts: localhost
  connection: local
vars:
    CentOS:
      ciphers: "a,b"
      hostkeys:
        - "ssh_host_key"
        - "ssh_rsa_host_key"
  tasks:

copy:
  dest: "{{ playbook_dir }}/test.out"
  content: |
# This works:
{{ CentOS.ciphers }}

# This results in 'No variable found with this name':
{{ lookup('vars', ansible_distribution + '.ciphers') }}

# Templating errors:
{% for hostkey in {{ lookup('vars', ansible_distribution + '.hostkeys') }} %}
{{ hostkey }}
{% endfor %}

# Templating errors:
{% for hostkey in {{ hostvars[inventory_hostname][ansible_distribution + '.hostkeys'] }} %}
{{ hostkey }}
{% endfor %}

What is the proper way to 'assemble' the variable names? Or is there a better way of doing this?

Answer 1

My question was answered by Martin Krizek, in the Ansible newsgroup. The correct syntax is:

---
- hosts: localhost
  connection: local
vars:
    CentOS:
      hostkeys:
        - "ssh_host_key"
        - "ssh_rsa_host_key"
  tasks:

copy:
  dest: "{{ playbook_dir }}/test.out"
  content: |
    {% for hostkey in lookup('vars', ansible_distribution)['hostkeys'] %}
    {{ hostkey }}
    {% endfor %}