How to trigger handlers (notify) when using import_tasks? - ansible

Question

When using notify on a task using import_tasks the handlers are not fired. I'm wondering why. tags are working like expected.
How to trigger handlers on imported tasks?
Example:
playbook test.yml:
- hosts: all
gather_facts: no
handlers:
- name: restart service
debug:
msg: restart service
tasks:
- import_tasks: test_imports.yml
notify: restart service
tags: test
test_imports.yml
- name: test
debug:
msg: test
changed_when: yes
- name: test2
debug:
msg: test2
changed_when: yes
Expected:
> ansible-playbook -i localhost, test.yml
PLAY [all] *************************************************************************************************************
TASK [test] ************************************************************************************************************
changed: [localhost] => {
"msg": "test"
}
TASK [test2] ***********************************************************************************************************
changed: [localhost] => {
"msg": "test2"
}
RUNNING HANDLER [restart service] **************************************************************************************
ok: [localhost] => {
"msg": "restart service"
}
...
Actual:
> ansible-playbook -i localhost, test.yml
PLAY [all] *************************************************************************************************************
TASK [test] ************************************************************************************************************
changed: [localhost] => {
"msg": "test"
}
TASK [test2] ***********************************************************************************************************
changed: [localhost] => {
"msg": "test2"
}
...

Answer 1

This question has been partially answered in Ansible's bug tracker here:
import_tasks is processed at parse time and is effectively replaced by the tasks it imports. So when using import_tasks in handlers you would need to notify the task names within.
Source: mkrizek's comment: https://github.com/ansible/ansible/issues/59706#issuecomment-515879321
This has been also further explained here:
imports do not work like tasks, and they do not have an association between the import_tasks task and the tasks within the imported file really. import_tasks is a pre-processing trigger, that is handled during playbook parsing time. When the parser encounters it, the tasks within are retrieved, and inserted where the import_tasks task was located. There is a proposal to "taskify" includes at ansible/proposals#136 but I don't see that being implemented any time soon.
Source: sivel comment: https://github.com/ansible/ansible/issues/64935#issuecomment-573062042
And for the good part of it, it seems it has been recently fixed: https://github.com/ansible/ansible/pull/73572
But, for now, what would work would be:
- hosts: all
gather_facts: no
handlers:
- name: restart service
debug:
msg: restart service
tasks:
- import_tasks: test_imports.yml
tags: test
And a test_imports.yml file like:
- name: test
debug:
msg: test
changed_when: yes
notify: restart service
- name: test2
debug:
msg: test2
changed_when: yes
notify: restart service
This all yields:
PLAY [all] *******************************************************************************************************
TASK [test] ******************************************************************************************************
changed: [localhost] =>
msg: test
TASK [test2] *****************************************************************************************************
changed: [localhost] =>
msg: test2
RUNNING HANDLER [restart service] ********************************************************************************
ok: [localhost] =>
msg: restart service
PLAY RECAP *******************************************************************************************************
localhost : ok=3 changed=2 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Then if you want to import those tasks somewhere this handler is not defined you could use the environment variable ERROR_ON_MISSING_HANDLER that helps you transform the error thrown when there is a missing handler to a "simple" warning.
e.g.
$ ANSIBLE_ERROR_ON_MISSING_HANDLER=false ansible-playbook play.yml -i inventory.yml
PLAY [all] *******************************************************************************************************
TASK [test] ******************************************************************************************************
[WARNING]: The requested handler 'restart service' was not found in either the main handlers list nor in the
listening handlers list
changed: [localhost] =>
msg: test
TASK [test2] *****************************************************************************************************
changed: [localhost] =>
msg: test2
PLAY RECAP *******************************************************************************************************
localhost : ok=2 changed=2 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0