Missing variable in jinja2, no output with Ansible - ansible

Question

I have an Ansible playbook that gathers facts from Cisco switches.
---
- hosts: switches
gather_facts: False
connection: network_cli
vars:
backup_root: ./configs
cli:
host: "{{ inventory_hostname }}"
tasks:
- name: ensure device folder is created
file:
path: "{{ backup_root }}/{{ inventory_hostname }}"
state: directory
- name: Gather all facts
cisco.ios.ios_facts:
gather_subset: all
- name: Serial Number
debug: var=ansible_net_serialnum
- name: Model
debug: var=ansible_net_model
- name: Hostname
debug: var=ansible_net_hostname
- name: Version
debug: var=ansible_net_version
- name: CDP
debug: var=ansible_net_neighbors
- name: Config file
debug: var=ansible_net_config
- name: Stack SW Model Numbs
debug: var=ansible_net_stacked_models
- name: Stack SW Model Numbs
debug: var=ansible_net_stacked_serialnums
- name: Get VLAN Info
cisco.ios.ios_command:
commands: show vlan brief
register: show_vlan
- name: get timestamp
command: date +%Y%m%d
register: timestamp
- name: Generate configuration files
template:
src=roles/discovery/templates/ios_switches.j2
dest="{{ backup_root }}/{{ inventory_hostname }}/{{ inventory_hostname }}.txt" `
Here is the jinja file.
Hostname: {{ ansible_net_hostname }}
Model: {{ansible_net_model}}
Serial Number: {{ansible_net_serialnum}}
IOS Version: {{ansible_net_version}}
IOS Image: {{ansible_net_image}}
Switch Stack Models:
{{ansible_net_stacked_models | to_nice_yaml(indent=2)}}
Switch Stack Serials:
{{ansible_net_stacked_serialnums | to_nice_yaml(indent=2)}}
CDP Neighbors:
{{ansible_net_neighbors | to_nice_yaml(indent=2)}}
Configuration:
{{ansible_net_config}}
VLAN:
{{show_vlan.stdout[0] | to_nice_yaml(indent=2)}}
This all works fine until it hits a switch that cannot stack (e.g. chassis or VSS). When I run the playbook, I get the following-
msg: 'AnsibleUndefinedVariable: ''ansible_net_stacked_models'' is undefined
I've tried using if in Jinja2 like the following
...
Switch Stack Models:
{% if ansible_net_stacked_models is not defined %}
NOT A STACKABLE SWITCH
{% else %}
{{ansible_net_stacked_models | to_nice_yaml(indent=2)}}
{% endif %}
however it fails in the Jinja rendering and does not produce any output.
Is there a way to ignore missing variables in jinja or is there a better way to do this?

Answer 1

you can set a default value to your variable if is not defined
{{ ansible_net_stacked_models|default("NOT A STACKABLE SWITCH", true) | to_nice_yaml(indent=2) }}

Answer 2

Come to find out the error was stopping Ansible from even calling the jinja file. I dug around some more and found that I could set the variable to a default value in the inventory.
[switch:vars]
ansible_net_stacked_models='NOT A STACKABLE SWITCH'
When running the playbook if the device has valid info it will overwrite the default variable we defined in inventory. If the device doesn't have valid info, Ansible will simply pass the default variable we set in inventory, over to jinja2.