Conditionnal 'changed_when' based on output in a 'with_items' task - loops

Question

I have a simple shell task which is feed with_items. I want to have the 'changed' status only when the run actually did something. So for that I have to parse the output and look for a «Done».
The issue is using a register at the same time that the with_items generates a list of results. And I don't find a way to access the stdout of the current loop iteration.
---
- name: Test to set changed status only on when output match with 'Done'
hosts: my-host-01
gather_facts: no
tasks:
- name: Task doing stuff
shell: |
echo {{ item }}
register: do_stuff
with_items:
- "Doing... Done!"
- "Nothing to do"
#changed_when: do_stuff.results[{{ item.id }}].stdout.find('Done')
- name: Print 'do_stuff' var to debug
debug:
var: do_stuff
- name: Try to access to the desired stdout
debug:
var: do_stuff.results[0].stdout
The expected result that I want would be:
TASK [Task doing stuff]
*************************************************************************
changed: [cnode02] => (item=Doing... Done!)
Ok: [cnode02] => (item=Nothing to do)

Answer 1

I had a similar problem and the following example from the ansible documentation was very helpful to understand it:
During iteration, the result of the current item will be placed in the
variable:
- shell: echo "{{ item }}"
with_items:
- one
- two
register: echo
changed_when: echo.stdout != "one"
https://docs.ansible.com/ansible/2.4/playbooks_loops.html#using-register-with-a-loop
In your case the condition with stdout.find(...) will not work. I successfully tested it with '"string" in var.stdout':
- name: Task doing stuff
shell: |
echo {{ item }}
register: do_stuff
with_items:
- "Doing... Done!"
- "Nothing to do"
changed_when: '"Done" in do_stuff.stdout'

Answer 2

The following example works using the changed_when: condition, for each item separately.
- name: Task doing stuff
shell: |
echo {{ item }}
register: task_result
with_items:
- "Doing... Done!"
- "Nothing to do"
changed_when: task_result.stdout | regex_search('Done')
In your task, you must use register: to store the result, e.g. register: task_result. During execution, especially for the changed_when: and failed_when: conditions, this is directly available via the variable name, i.e. via task_result.stdout.
Here you can now e.g. search for the desired text via function regex_search( ), or also for a certain line of the output. To search for a whole line, the function offers multiline=True as another parameter. More information about the function regex_search( ) can be found in the Ansible Docs.
As soon as the task with all its items has been executed, the result (as you assumed) is available in the variable task_result (i.e. under the same name) as a list via the key results, i.e. via task_result.results[ITEM_ID].stdout.