Conditionally registered variables are considered defined, even when the condition is false - variables

Question

Apologies for lack of clarify, rewriting my ask:
I am struggling to get the appropriate start_index value passed on to the third task below "Echo parameters". If user_defined_index is "" I want the echo unique UIDs task to execute and output passed in the start_index variable. Likewise if user_define_index is not "" I want the second task below to execute and populate the start_index variable. I essentially need to pass either A or B to the echo parameters task.
The Echo parameters task expects to get some UIDs. The first task autogenerates UIDs based on what you see in the shell command. the second task allows for user to specify UIDs. So whichever WHEN command is valid that set of UIDs need to get used by the third task. Using debug statements I have confirmed that both ECHO UNIQUE UIDS and CAPTURE USER DEFINED UIDs tasks work fine and the corresponding register variables have the right data.
My issue is 3rd task only picks up values from the 1st task regardless, whether it be auto generated values or blank with skipped equals true.
I need the correct corresponding value in the start_index to be fed into the 3rd task.
- name: echo unique UIDs
shell: echo $(((0x$(hostid) + $(date '+%s'))*100000 + {{ item[0] }}*100000 + {{ start_stress_index }}))
with_indexed_items:
- "{{ load_cfg }}"
register: start_index
when: user_defined_index == ""
changed_when: False
- name: Capture user defined UIDs
shell: echo '{{ user_defined_index }}' | tr , '\n'
with_indexed_items:
- "{{ load_cfg }}"
register: start_index
when: user_defined_index != ""
changed_when: False
- name: Echo parameters
command: echo --cfg='{{ start_index }}' --si={{ item[1].stdout }}
with_together:
- "{{ load_cfg }}"
- "{{ start_index.results }}"
For the above regardless of user_define_index output from the echo unique UIDs always gets passed through to the 3rd task. After googling I finally found a potential solution to use the ternary filter:
https://github.com/ansible/ansible/issues/33827
I have modified my code to be:
- name: echo unique UIDs
shell: echo $(((0x$(hostid) + $(date '+%s'))*100000 + {{ item[0] }}*100000 + {{ start_stress_index }}))
with_indexed_items:
- "{{ load_cfg }}"
register: start_auto_index
when: user_defined_index == ""
changed_when: False
- name: Capture user defined UIDs
shell: echo '{{ user_defined_index }}' | tr , '\n'
with_indexed_items:
- "{{ load_cfg }}"
register: start_user_index
when: user_defined_index != ""
changed_when: False
- name: Echo parameters
command: echo --cfg='{{ start_index }}' --si={{ item[1].stdout }}
with_together:
- "{{ load_cfg }}"
- "{{ ((start_auto_index is not skipped)|ternary(start_auto_index,start_user_index))['results'] }}"
However, I still have same issue as with my first example when i run the above I again only get output from start_auto_index sent to 3rd task echo parameters no matter what i do with user_defined_index.
I hope this clarifies my question.

Answer 1

Explanation
The problem is that your tasks contain a loop and in such case Ansible returns separate statuses for the task and each loop iteration.
With start_auto_index is not skipped you check the status of the whole task, but it is iterations that get status "skipped".
Solution
Since your conditional user_defined_index for the tasks containing the loop is constant for each loop iteration, all iterations will have the same skipped-status, you can modify the condition in the Echo parameters task to checking just one of them:
"{{ ((start_auto_index[0] is not skipped)|ternary(start_auto_index,start_user_index))['results'] }}"
Besides, in the Echo parameters task with_together does not seem to serve any function, as you don't refer to the item[0].