Ansible single task variable on top of global variable - ansible

Question

I have a playbook where I am configuring environment variables for multiple hosts.
these are the global vars set in defaults\main.yml:
environment:
http_proxy: blabla
https_proxy: blabla
Now I have a single task where I need to set another environment variable for the python library.
However, when I set the environment var for that single task it overwrites the global environment vars.
- name: some task
command: command
environment:
ENV_VAR: "blabla"
I want the ENV_VAR for the single task to be added on top of the global vars. But is that even possible?
https://docs.ansible.com/ansible/latest/user_guide/playbooks_environment.html
this page didn't give me anything conclusive.
Could I use the with_items option to achieve this possibly?

Answer 1

The following playbook demonstrates a possible implementation for your requirement using the combine filter associated with default. Run this with -v option to see output of shell commands:
---
- name: Parse several results as json strings
hosts: localhost
gather_facts: false
# This will automatically combine `default_env` (default to empty if it does not exists)
# with `more_env` if this latest var is defined somewhere
environment: "{{ default_env | default({}) | combine(more_env | default({})) }}"
vars:
# Define default environment variables
default_env:
http_proxy: blabla
https_proxy: blabla
tasks:
- name: Show some vars
vars:
# Inject more environment variables for this task
more_env:
toto: titi
shell: |-
echo $http_proxy
echo $https_proxy
echo $toto
- name: Same with default env
shell: |-
echo $http_proxy
echo $https_proxy
echo $toto
Which gives:
$ ansible-playbook test.yml -v
PLAY [Default env override] ****************************************************************************************************************************************************************************************************************************
TASK [Show some vars] ***************************************************************************************************************************************************************************************************************************************************
changed: [localhost] => {"changed": true, "cmd": "echo $http_proxy\necho $https_proxy\necho $toto", "delta": "0:00:00.002207", "end": "2020-01-07 09:57:30.178989", "rc": 0, "start": "2020-01-07 09:57:30.176782", "stderr": "", "stderr_lines": [], "stdout": "blabla\nblabla\ntiti", "stdout_lines": ["blabla", "blabla", "titi"]}
TASK [Same with default env] ********************************************************************************************************************************************************************************************************************************************
changed: [localhost] => {"changed": true, "cmd": "echo $http_proxy\necho $https_proxy\necho $toto", "delta": "0:00:00.001875", "end": "2020-01-07 09:57:30.626163", "rc": 0, "start": "2020-01-07 09:57:30.624288", "stderr": "", "stderr_lines": [], "stdout": "blabla\nblabla", "stdout_lines": ["blabla", "blabla"]}
PLAY RECAP **************************************************************************************************************************************************************************************************************************************************************
localhost : ok=2 changed=2 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0