defaulting on undefined nested dictionaries

Archives Ansible Project
1

Hi all,

I have a dictionary with a nested dictionary defined in defaults/main.yml of my role:

file_system_system_vg: name: "A Name" lv: {}

where lv is the nested dictionary.

I can use the nested dictionary in a task like this:
``

`

  • name: Create Logicals Volumes on primary VG
    lvol: vg={{ file_system_system_vg.name }} lv={{ item.value.name }} size={{ item.value.size }}
    with_dict: file_system_system_vg.lv
    `

This all works fine when file_system_system_vg is defined, but i would like to remove it from defaults/main.yml and only run the task when file_system_system_vg.**lv** is defined elsewhere, so I have tried this:

`

  • name: Create Logicals Volumes on primary VG
    lvol: vg={{ file_system_system_vg.name }} lv={{ item.value.name }} size={{ item.value.size }}
    with_dict: file_system_system_vg.lv | default ({})
    `

but it throws an error:

TASK: [file_system | Create Logicals Volumes on primary VG] ******************* fatal: [dsdptgfc06v.devqa.exch.int] => with_dict expects a dict

Please note that file_system_system_vg is not defined here and neither is``file_system_system_vg.lv.Does this make sense?
How can I make ansible skip this task when bothfile_system_system_vgand``file_system_system_vg.lvare undefined?
N.B when I run the task I need to use the dictionaries within file_system_system_vg.lv

Thanks in advance
Paddy

2

have you tried:

with_dict: "{{ file_system_system_vg is
defined>ternary(file_system_system_vg.lv|default({}), {})}}"

?

3

Hi Brian,

so in my defaults/main.yml if I define only this:

file_system_system_vg:

It works! so we are nearly there. If I remove file_system_system_vg from defaults/main.yml it throws an error again:

`

TASK: [file_system | Create Logicals Volumes on primary VG] *******************
fatal: [dsdptgfc06v.devqa.exch.int] => with_dict expects a dict

PLAY RECAP *******************************************************************
`

So is it possible to remove file_system_system_vg completely from defaults/main.yml?

Thanks
Patrick

4

I made a simple playbook to show the issue. It seems ansible evalutes all variables regardless of the conditional result before ternary.
If you run the playbook twice, once with "simpleDict" defined, and again with it commented out.``

`

5

You can specify default values for both the dictionary in which you are trying to look something up, and the key you are looking up:

with_dict: (file_system_system_vg|default({})).lv|default({})

The parentheses are important!

6

It works, exactly what I was after! Thanks Christian

Patrick