[ansible] How to keep null value?

keep-null-value.md

My playbook:

---
- hosts: "localhost"
  connection: "local"
  gather_facts: false
  vars:
    x: null
    y:
      z: null
    var1: "{{ x }}"
    var2: "{{ y.z }}"
  tasks:
    - debug:
        msg: |
          {% if (var1 | default(none)) is none %}
          var1 is none/null
          type: {{ var1 | type_debug }}
          {% else %}
          var1 is NOT none/null
          type: {{ var1 | type_debug }}
          value: [{{ var1 }}]
          {% endif %}
    - debug:
        msg: |
          {% if (var2 | default(none)) is none %}
          var2 is none/null
          type: {{ var2 | type_debug }}
          {% else %}
          var2 is NOT none/null
          type: {{ var2 | type_debug }}
          value: [{{ var2 }}]
          {% endif %}

My test:

$ ansible --version
ansible [core 2.11.6] 
  config file = /workdir/ansible.cfg
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.8/site-packages/ansible
  ansible collection location = /root/.ansible/collections:/usr/share/ansible/collections
  executable location = /usr/local/bin/ansible
  python version = 3.8.10 (default, Jun 23 2021, 15:19:53) [GCC 8.3.0]
  jinja version = 3.0.3
  libyaml = True

$ ansible-playbook quick.yml -i 'localhost,'
[WARNING]: Unable to parse localhost, 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 [debug] ************************************************************************
ok: [localhost] => {
    "msg": "var1 is none/null\ntype: NoneType\n"
}

TASK [debug] ************************************************************************
ok: [localhost] => {
    "msg": "var2 is NOT none/null\ntype: str\nvalue: []\n"
}

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

1. Why var2 is not none/null?
2. How to pass/keep the none/null value to var2?

Solved:

• with export ANSIBLE_JINJA2_NATIVE=1 environment variable during the Ansible run.
• or with jinja2_native = 1 in ansible.cfg in the [defaults] section.

See https://docs.ansible.com/ansible/latest/reference_appendices/config.html#default-jinja2-native.

Note: jinja2_native option is enabled by default since ansible-core 2.12.0.