Ansible "stat" module doesn't work with the when clause - module

Question

I have a playbooks that checks to see if the endpoint is registered to Spacewalk using the stat module
- name: "Check spacewalk registraton"
stat:
path: /usr/sbin/rhn_check
register: sw_registered
- debug:
msg: "{{ sw_registered }}"
Output is:
TASK [Check spacewalk registraton] *********************************************
ok: [hostname]
TASK [debug] *******************************************************************
ok: [hostname] =>
msg:
changed: false
failed: false
stat:
atime: 1670244246.6493175
attr_flags: e
attributes:
- extents
block_size: 4096
blocks: 32
charset: us-ascii
checksum: 7b22e2e756706ef1b81e50cda7c41005e15441d7
ctime: 1623819058.4283004
dev: 64768
device_type: 0
executable: true
**exists: true**
gid: 0
gr_name: root
inode: 143991
isblk: false
ischr: false
isdir: false
isfifo: false
isgid: false
islnk: false
isreg: true
issock: false
isuid: false
mimetype: text/x-python
mode: '0755'
mtime: 1536233638.0
nlink: 1
path: /usr/sbin/rhn_check
pw_name: root
readable: true
rgrp: true
roth: true
rusr: true
size: 15291
uid: 0
version: '290956743'
wgrp: false
woth: false
writeable: true
wusr: true
xgrp: true
xoth: true
xusr: true
So the sw_registered.stat.exists is a value of true
Further in my role are tasks based on this variable
- name: "Yum update for RHEL6 and above using RedHat Satellite"
yum:
name: '*'
state: latest
exclude: rhn-client-tools
when: (ansible_distribution_major_version >= "6") and (sw_registered.stat.exists is not defined and sw_registered.stat.exists is false)
Output from that task is
TASK [QL-patching : Yum update for RHEL6 and above using RedHat Satellite] *****
skipping: [hostname]
I would expect that task to be skipped but the next task is:
- name: "Yum update for RHEL6 and above using spacewalk"
yum:
name: '*'
state: latest
disable_gpg_check: yes
when: (ansible_distribution_major_version >= "6") and (sw_registered.stat.exists is defined and sw_registered.stat.exists is true )
Output from that task is:
TASK [QL-patching : Yum update for RHEL6 and above using spacewalk] ************
skipping: [hostname]
I expect this task be executed and not skipped. What am I missing here?

Answer 1

Based on the comment of Zeitounator you may have a look into the following minimal example
---
- hosts: localhost
become: false
gather_facts: false
tasks:
- name: Test file
stat:
path: "/home/{{ ansible_user }}/test.file"
register: result
- name: Show result
debug:
msg: "{{ result.stat.exists }}"
resulting into an output of
TASK [Show result] ******
ok: [localhost] =>
msg: false
TASK [Show result] ******
ok: [localhost] =>
msg: true
and depending on if the file to test exists or not.
The key result.stat.exists will be defined in both cases if the stat test task was executed successful. This is because of Return Values of the stat module. Therefore the Conditional task based on registered variables could be simplified to something like
- name: Show result
debug:
msg: "File exists."
when: result.stat.exists
resulting into an output of
TASK [Show result] ******
ok: [localhost] =>
msg: File exists.
if the file is available or skipped if not.
You may also consinder to Provide default values as also mentioned and to catch corner cases like a former failing task because of insufficient access rights or if the task wasn't running because of Check mode. In such cases the result set could look like
TASK [Test file] ***************************
fatal: [localhost]: FAILED! => changed=false
msg: Permission denied
...ignoring
TASK [Show result] *************************
ok: [localhost] =>
msg:
changed: false
failed: true
msg: Permission denied