How to use omit with Ansible and avoid any errors?

Question

I tried to use omit with an expression like this:

id: "{{ openstack_networks.id | default(omit) }}"

But it seems that it keeps failing with an exception when openstack_networks variable is not defined.

What is the correct way to write this jinja2 filter?

I want to omit the parameter in case openstack_networks.id does not exists.

I was trying to get my head around why an existing ansible playbook was using `some.thing | default() or omit` instead of simply `some.thing | default( omit )` and ended up here. However, best as I can tell, ansible 7 appears to happily accept the latter incantation now. — cueedee, Feb 14 '23 at 08:12

Kuba hasn't forgotten Monica · Answer 1 · 2022-12-23T22:18:12.223

22

Interestingly enough, Ansible will take something that reads like plain English:

id: "{{ omit if openstack_networks.id is not defined else openstack_networks.id }}"

The benefit here is that there are no additional parentheses.

edited Dec 23 '22 at 22:18

answered Mar 13 '19 at 21:15

score 14 · Accepted Answer · answered Jan 18 '17 at 19:06

14

Not super elegant, but 100% working solution to handle keys of possibly undefined parent dicts:

id: "{{ (openstack_networks | default({})).id | default(omit) }}"

This will give you omit if openstack_networks is defined but has no id key or if openstack_networks is undefined.

answered Jan 18 '17 at 19:06

2

Thanks. Now my head hurts! There is no beauty in Ansible :( – sorin Jan 18 '17 at 19:57

2 Answers2