Create Ansible host vars dump for all hosts

dump.j2

{
{% for host in groups.all %}
    "{{ host }}": {{ hostvars[host]|to_json }}{{ ',' if not loop.last else '' }}
{% endfor %}
}

dump.yml

---
- hosts: all
  gather_facts: true
  tasks:
    - name: Create hostvars dump
      copy:
        content: "{{ lookup('template', 'dump.j2')|from_json|to_nice_json }}"
        dest: ./dump.json
      run_once: true