mbuil

output.log

$ ansible-playbook test.yml
 [WARNING]: Unable to parse /etc/ansible/hosts as an inventory source

 [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 [set_fact] **********************************************************************************************************************************
ok: [localhost]

TASK [debug] *************************************************************************************************************************************
ok: [localhost] => {
    "msg": {
        "address": "2.2.2.2"
    }
}

PLAY RECAP ***************************************************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0

$ ansible-playbook test.yml -e mgmt_vlan=native
 [WARNING]: Unable to parse /etc/ansible/hosts as an inventory source

 [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 [set_fact] **********************************************************************************************************************************
ok: [localhost]

TASK [debug] *************************************************************************************************************************************
ok: [localhost] => {
    "msg": {
        "address": "1.1.1.1"
    }
}

PLAY RECAP ***************************************************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0

test.yml

- hosts: localhost
  connection: local
  gather_facts: no
  vars:
    mgmt_interface: eth0
    mgmt_vlan: 10
    device:
      "eth0":
        address: "1.1.1.1"
      "eth0.10":
        address: "2.2.2.2"
  tasks:
    - set_fact:
        device_to_get: "{{ (mgmt_vlan == 'native') | ternary(mgmt_interface, mgmt_interface ~ '.' ~ mgmt_vlan) }}"
    - debug:
        msg: "{{ device[device_to_get] }}"

    - debug:
        msg: >-
          {%- if mgmt_vlan == 'native' %}
          {%-   set device_to_get2 = mgmt_interface %}
          {%- else %}
          {%-   set device_to_get2 = mgmt_interface ~ '.' ~ mgmt_vlan %}
          {%- endif %}
          {{- device[device_to_get2] }}