The task includes an option with an undefined variable. The error was: 'domains' is undefined.

TASK [coopdevs.certbot_nginx : Compare domains with domains in certificate] **************************************************************************
fatal: [server-name]: FAILED! => {"msg": "The task includes an option with an undefined variable. The error was: 'domains' is undefined. 'domains' is undefined\n\nThe error appears to be in '/home/user/.ansible/roles/coopdevs.certbot_nginx/tasks/certificate.yml': line 29, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: Compare domains with domains in certificate\n ^ here\n"}

Offending task code:

```
- name: Compare domains with domains in certificate
set_fact:
certbot_force_update: "{{ old_domains | symmetric_difference(domains) | length | bool }}"
when: certbot_force_update is not defined
```

Start in tasks/certificate.yml at the “Compare domains with domains in certificate” task and inspect how its variables are defined elsewhere in the role. Reproduce the task to confirm the undefined-variable failure, then verify that certificate domain comparison completes without that error.

Written by the indexing model from the issue text.