Beware of the difference between vars and facts

[ericzolf]

Small quiz, who can guess what happens before trying, and explain why:

---
- name: show an important difference between vars and facts
  hosts: localhost
  gather_facts: false
  become: false

  vars:
    some_var: "{{ lookup('password', '/dev/null') }}"

  tasks:
    - name: define now a fact
      set_fact:
        some_fact: "{{ lookup('password', '/dev/null') }}"
    - name: output now the fact twice
      debug:
        msg: "{{ some_fact }} vs. {{ some_fact }}"
    - name: output again the fact
      debug:
        var: some_fact
    - name: output now the variable also twice
      debug:
        msg: "{{ some_var }} vs. {{ some_var }}"
    - name: output again the variable (uups!)
      debug:
        var: some_var