I'm looking for the way how to make Ansible to analyze playbooks for required and mandatory variables before run playbook's execution like:

```
- name: create remote app directory hierarchy
  file:
    path: "/opt/{{ app_name | required }}/"
    state: directory
    owner: "{{ app_user | required }}"
    group: "{{ app_user_group | required }}"
  ...

```

and rise error message if variable is undefined, like:

```
please set "app_name" variable before run (file XXX/main.yml:99)

```