Conditionals against variables - linux

Question

I am building a snapshot management playbook and that checks for an existing snap before taking a snap. I am having trouble testing a conditional when the playbook finds an existing snap. Here is a sample code:
---
- name: Test Snapshot
hosts: axwayT
gather_facts: false
vars_files:
- vault/creds.yml
vars:
mail_body_file: "/tmp/ansible_mail"
pre_tasks:
- name: Delete mail body file
file:
state: absent
path: "{{ mail_body_file }}"
delegate_to: localhost
run_once: true
- name: Create mail body file
file:
state: touch
path: "{{ mail_body_file }}"
delegate_to: localhost
run_once: true
tasks:
- name: find guest's folder using name
vmware_guest_find:
hostname: "{{ vcenter_hostname }}"
username: "{{ vcenter_username }}"
password: "{{ vcenter_password }}"
validate_certs: no
name: "{{ vcenter_hostgroup_name }}"
datacenter: "{{ datacenter_name }}"
register: vm_folder
delegate_to: localhost
- name: Check for existing snapshots
vmware_guest:
hostname: "{{ vcenter_hostname }}"
username: "{{ vcenter_username }}"
password: "{{ vcenter_password }}"
validate_certs: no
name: "{{ vcenter_hostgroup_name }}"
datacenter: "{{ datacenter_name }}"
folder: "{{vm_folder.folders[0]}}"
name: "{{ vcenter_hostgroup_name }}"
state: present
register: vm_state
delegate_to: localhost
- name: debug
debug:
var: vm_state.instance.current_snapshot
- name: Test
shell: echo "Found!"
when: vm_state.instance.current_snapshot !=""
I am working with an inventory of two servers for testing, nothing special. Here is the ouput I want to use a conditional against:
TASK [debug] ********************************************************************************************************************************************************************************************************************************
ok: [swipe901.test.com] => {
"vm_state.instance.current_snapshot": ""
}
ok: [swipe902.test.com] => {
"vm_state.instance.current_snapshot": {
"creation_time": "2023-02-07T21:14:06.812901+00:00",
"description": "",
"id": 13,
"name": "VM Snapshot 2%2f7%2f2023, 3:14:05 PM",
"state": "poweredOn"
}
}
I tried two when statements:
when: vm_state.instance.current_snapshot =""
when: vm_state.instance.current_snapshot is defined
My logic is way off and I am seeing my own limitations with programing logic, which I plan to fix soon.
My plan for the logic is to, skip a step, in my playbook if vm_state.instance.current_snapshot is "". How would this be handled?

Answer 1

Q: "I would like the condition to evaluate false if there is anything populated in current_snapshot."
A: For example, the playbook
shell> cat pb.yml
- name: Evaluate false if there is anything populated in current_snapshot
hosts: localhost
tasks:
- debug:
msg: The variable current_snapshot is either empty or does not exist.
when: current_snapshot|d('', true)|length == 0
gives
shell> ansible-playbook pb.yml
PLAY [Evaluate false if there is anything populated in current_snapshot] *************************************************************
TASK [debug] *************************************************************************************************************************
ok: [localhost] =>
msg: The variable current_snapshot is either empty or does not exist.
PLAY RECAP ***************************************************************************************************************************
localhost: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
shell> ansible-playbook pb.yml -e current_snapshot=''
PLAY [Evaluate false if there is anything populated in current_snapshot] *************************************************************
TASK [debug] *************************************************************************************************************************
ok: [localhost] =>
msg: The variable current_snapshot is either empty or does not exist.
PLAY RECAP ***************************************************************************************************************************
localhost: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
shell> ansible-playbook pb.yml -e current_snapshot='anything'
PLAY [Evaluate false if there is anything populated in current_snapshot] *************************************************************
TASK [debug] *************************************************************************************************************************
skipping: [localhost]
PLAY RECAP ***************************************************************************************************************************
localhost: ok=0 changed=0 unreachable=0 failed=0 skipped=1 rescued=0 ignored=0
You can also use assert. For example,
shell> cat pb.yml
- name: Evaluate false if there is anything populated in current_snapshot
hosts: localhost
tasks:
- assert:
that: current_snapshot|d('', true)|length == 0
success_msg: The variable current_snapshot is either empty or does not exist.
fail_msg: The variable current_snapshot is populated.