Conditional to add_host module - ansible

Question

I have an inventory that i need to add a conditional to.
My code:
- name: Create memory inventory
add_host:
name: "{{ item.0.key }}"
group: target_hosts
with_nested:
- "{{ lookup ('dict', hosts, wantlist=True) }}"
But I want something like:
- name: Create memory inventory
add_host:
name: "{{ item.0.key }}"
{% if item.0.value.OS_Choice[:3] == 'win' %}
group:
- target_hosts
- win
{% else %}
group:
- target_hosts
- linux
{% endif %}
with_nested:
- "{{ lookup ('dict', hosts, wantlist=True) }}"
With this configuration, Ansible errors:
The offending line appears to be:
{% if item.0.value.OS_Choice[:3] == 'win' %}
^ here
Any ideas on how I can implement this conditional?

Answer 1

You're mixing up Jinja2 with YAML. Here you go:
- name: Create memory inventory when win
add_host:
name: "{{ item.0.key }}"
with_nested:
- "{{ lookup ('dict', hosts, wantlist=True) }}"
when: item.0.value.OS_Choice[:3] == 'win'
vars:
group:
- target_hosts
- win
- name: Create memory inventory when not win
add_host:
name: "{{ item.0.key }}"
with_nested:
- "{{ lookup ('dict', hosts, wantlist=True) }}"
when: item.0.value.OS_Choice[:3] != 'win'
vars:
group:
- target_hosts
- linux
However, Ansible gather facts about the OS already. Perhaps you want to use those, instead of configuring something like this yourself.

Answer 2

Building up on Kevin's answer (and fixing some wrongly placed parameters)
You should definitely do this differently, like creating dynamic groups based on detected OS in facts. See:
the group_by module
the ansible_distribution* facts that you can explore as an example with
ansible localhost -m setup -a filter="ansible_distribution*"
Meanwhile, with your current logic, you can still do this in a single task:
- name: Create memory inventory
vars:
additional_group: >-
{{ (item.0.value.OS_Choice[:3] == 'win') | ternary('win', 'linux') }}
add_host:
name: "{{ item.0.key }}"
groups:
- target_hosts
- "{{ additional_group }}"
with_nested:
- "{{ lookup ('dict', hosts, wantlist=True) }}"