How to validate variables contents in Ansible?

ansible-lint only checks the tasks/handlers and doesn't iterate over the variables (e.g. if you're using with_items, it won't iterate over all the items) and yamllint only checks cosmetic issues and is hard to customized with custom rules.

Is there a tool that can validate the actual data in the variables in YAML files before they are fed into Ansible?

Examples:

• A given variable cannot contain a specific string
• Variable user_ssh_key fed to authorized_keys cannot have a comment
• Variable ssh_enabled fed to service module cannot be True
• and so on...

You can use assert and testing-strings to achieve that.

Like so:

- hosts: localhost
  vars:
    variable: 'green'
  tasks:
    - assert:
        that: variable is match("green")
        success_msg: "Variable is green"
        fail_msg: "Variable is not green"

You can

match strings against a substring or a regular expression, use the match, search or regex tests