Ansible not setting environment variable correctly - ansible

Question

I trying to set an environment variable for an ansible play.
Based on this, I should be able to do something like:
---
- hosts: localhost
connection: local
environment:
test_var: "a vault here"
tasks:
- debug:
msg: "Test var is: {{lookup('env', 'test_var')}}"
- debug:
msg: "Home is here {{lookup('env', 'HOME')}}"
But I am clearly missing something or encountered a bug?
osboxes#osboxes:~$ ansible-playbook --version
ansible-playbook 2.9.6
<snip...>
osboxes#osboxes:~$ ansible-playbook test.yaml
<snip...>
TASK [debug] ****************************************************************************************************************************************************************
ok: [localhost] => {
"msg": "Test var is: " # where is the env variable?
}
TASK [debug] ****************************************************************************************************************************************************************
ok: [localhost] => {
"msg": "Home is here /home/osboxes"
}

Answer 1

When you set env using environment plugin, you do not affect the ansible session which is already running.
You would have to do as follow:
---
- hosts: localhost
connection: local
environment:
test_var: "a vault here"
tasks:
- shell: echo $test_var
register: test_var
- debug:
msg: "Test var is: {{ test_var.stdout }}"
- debug:
msg: "Home is here {{lookup('env', 'HOME')}}"
The above playbook would return the following output:
PLAY [localhost] ****************************************************************************************************************************************************
TASK [Gathering Facts] **********************************************************************************************************************************************
ok: [localhost]
TASK [shell] ********************************************************************************************************************************************************
changed: [localhost]
TASK [debug] ********************************************************************************************************************************************************
ok: [localhost] => {
"msg": "Test var is: a vault here"
}
TASK [debug] ********************************************************************************************************************************************************
ok: [localhost] => {
"msg": "Home is here /home/ps"
}
PLAY RECAP **********************************************************************************************************************************************************
localhost : ok=4 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Note: See this link to official documents.
When you set a value with environment: at the play or block level, it
is available only to tasks within the play or block that are executed
by the same user. The environment: keyword does not affect Ansible
itself, Ansible configuration settings, the environment for other
users, or the execution of other plugins like lookups and filters.
Variables set with environment: do not automatically become Ansible
facts, even when you set them at the play level. You must include an
explicit gather_facts task in your playbook and set the environment
keyword on that task to turn these values into Ansible facts.
Important points to highlight in the above text:
The environment: keyword does not affect Ansible itself, Ansible
configuration settings, the environment for other users, or the
execution of other plugins like lookups and filters