Module 'group_by' report changed even with 'changed_when: false'

[chemnic]

SUMMARY

After upgrade from 2.9.10 to 2.9.11 I noticed the module 'group_by' is reporting 'changed'.
This is because this change in #69860
The problem is that it is reporting 'changed' even with changed_when: false added to the task.

ISSUE TYPE

• Bug Report

COMPONENT NAME

group_by

ANSIBLE VERSION

2.9.11

CONFIGURATION

OS / ENVIRONMENT

Ubuntu 18.04 (control and target host)

STEPS TO REPRODUCE

As an example use the task:

- group_by:
    key: "os_{{ ansible_facts['distribution_file_variety'] }}"
  changed_when: false
  register: groupby

- debug:
    msg: "{{ groupby }}"

TASK [group_by_os : group_by] *******************************************************************************************************************************
changed: [srvd-test04]

TASK [group_by_os : debug] **********************************************************************************************************************************
ok: [srvd-test04] => 
  msg:
    add_group: os_Debian
    changed: true
    failed: false
    parent_groups:
    - all

PLAY RECAP **************************************************************************************************************************************************
srvd-test04                : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0 

EXPECTED RESULTS

The task should always return changed: false

ACTUAL RESULTS

The task return changed: true

[ansibot]

Files identified in the description:

• lib/ansible/modules/group_by.py

If these files are incorrect, please update the component name section of the description or use the !component bot command.

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[bcoca]

note: this is a bit complicated as we evaluate changed/failed_when on the child before passing the results to the parent process, but the parent takes care of 'special' tasks like group_by/add_host/meta/etc and has not way to re-evalute those conditionals.

[chemnic]

I tested the fix with devel+commits and can confirm is working.