How to detect if host is WSL in Ansible playbook?

Question

In Ansible, I need to run some roles only if the host is a WSL host.

How to detect that? I am looking for a form of:

- name: "Run only in WSL"
  when: # what to put here?
  # task definition

What to put in the when section? I am looking for a way to detect that automatically, NOT to configure a variable on my host in the inventory.

Answer 1

Just gather Ansible facts. There is no need for command, shell, register and parse stdout at all. From a minimal example playbook

---
- hosts: test
  become: true

  gather_facts: true
  gather_subset:
    - "!all"
    - "min"
  # - "hardware"

  tasks:

  - name: Show Facts
    debug:
      msg: "{{ ansible_facts }}"

the output result will already contain the requested information

    os_family: RedHat
    product_name: VMware7,1
    system: Linux
    system_vendor: VMware, Inc.
    virtualization_role: guest
    virtualization_type: VMware

or

    os_family: RedHat
    product_name: Virtual Machine
    product_version: Hyper-V UEFI Release v1.0
    system: Linux
    system_vendor: Microsoft Corporation

or

    os_family: RedHat
    product_name: HVM domU
    system: Linux
    system_vendor: Xen
    virtualization_role: guest
    virtualization_type: xen

It also contains the ansible_facts.kernel versions

3.10.0-1160.108.1.el7.x86_64
4.18.0-513.11.1.el8_9.x86_64
5.14.0-362.18.1.el9_3.x86_64

With this information Conditionals based on ansible_facts is trivial. Like in

when: ansible_facts['os_family'] == "Debian" and ansible_facts['system_vendor'] == "Microsoft Corporation"