Checking whether nested variable is defined in the when statement

[Emmanuel Livingstone]

Nested data structures can be accessed either by indexing using the key name or dot syntax with the key name - https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#accessing-complex-variable-data

But I'm not able to access nested data structure from variables in the when statement. Here is a minimal sample to demonstrate the issue

# cat play.yml                                                                                                         

- hosts: localhost

  vars:

    parent:

      child1: true

  tasks:

  - name: "Check if variable is defined"

    fail:

      msg: "mandatory variable {{ item }} not passed as extra args when invoking playbook"

    when: item not in vars

    loop:

    - parent

    - parent.child1

    - parent.child2

Here is the sample output

ansible-playbook play.yml                                                                                             (livingstone-dev/monitoring)

 [WARNING]: No inventory was parsed, only implicit localhost is available

 [WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'

PLAY [localhost] *********************************************************************************************************************************************

TASK [Gathering Facts] ***************************************************************************************************************************************

ok: [localhost]

TASK [Check if variable is defined] **************************************************************************************************************************

skipping: [localhost] => (item=parent) 

failed: [localhost] (item=parent.child1) => {"ansible_loop_var": "item", "changed": false, "item": "parent.child1", "msg": "mandatory variable parent.child1 not passed as extra args when invoking playbook"}

failed: [localhost] (item=parent.child2) => {"ansible_loop_var": "item", "changed": false, "item": "parent.child2", "msg": "mandatory variable parent.child2 not passed as extra args when invoking playbook"}

PLAY RECAP ***************************************************************************************************************************************************

localhost                  : ok=1    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0 

Any idea how I can have nested variables in ansible when statements. 

[Vladimir Botka]

Hi Emmanuel,

On Mon, 16 Dec 2019 00:57:57 -0800 (PST)
Emmanuel Livingstone <livings...@gmail.com> wrote:

> vars:
> parent:
> child1: true
> tasks:
> - name: "Check if variable is defined"
> fail:
> msg: "mandatory variable {{ item }} not passed as extra args"

> when: item not in vars
> loop:
> - parent
> - parent.child1
> - parent.child2
>

> skipping: [localhost] => (item=parent)
> failed: [localhost] (item=parent.child1) => {"ansible_loop_var": "item",
> "changed": false, "item": "parent.child1", "msg": "mandatory variable
> parent.child1 not passed as extra args when invoking playbook"}

'json_query' returns 'False' when the parameter is not defined. 'set_fact'
before the evaluation to register the variable with 'hostvars'. For example

- set_fact:
parent: "{{ parent }}"

- fail:

msg: "mandatory variable {{ item }} not passed as extra args"

when: not hostvars[inventory_hostname]|json_query(item)

loop:
- parent
- parent.child1
- parent.child2

Cheers,

-vlado

[Emmanuel Livingstone]

Thanks Vladimir. I'm sure your solution works. I've figured out a simpler solution. Just posting it here for reference - https://stackoverflow.com/a/59367345/434678