Rendering Ansible template into the fact variable

I think you might be just looking for the template lookup plugin:

- set_fact:
    rendered_template: "{{ lookup('template', './template.j2') }}"

Usage example:

• template.j2

    Hello {{ value_for_template }}
  

• playbook.yml

    ---
    - hosts: localhost
      gather_facts: no
      connection: local
      vars:
        value_for_template: world
      tasks:
        - debug:
            var: rendered_template
          vars:
            rendered_template: "{{ lookup('template', './template.j2') }}"
  

• The result:

    TASK [debug] *******************************************************************
    ok: [localhost] => {
        "rendered_template": "Hello world\n"
    }