---

- name: Show how ansible defer variable evaluation to the last moment
  gather_facts: no
  hosts: localhost
  vars: 
    output: '{{ input }}'
  tasks:
  - set_fact:
      input: 'dummy'
  - set_fact:
      input: 'foo'
  - debug:
      var: output
  - assert:
      that:
      # "output" contains the value of "input" at the time it has been used
      - output == 'foo'
  - set_fact:
      input: bar
  - debug:
      var: output
  - assert:
      that:
      - output == 'bar'

- name: But the value of a fact is computed during assignation
  gather_facts: no
  hosts: localhost
  tasks:
  - set_fact:
      input: test1
  # Now "output" is not a variable but a fact
  - set_fact:
      output: '{{ input }}'
  - debug:
      var: output
  - assert:
      that:
      # "output" contains the value of "input" at the time it has been defined
      - output == 'test1'
  - set_fact:
      input: test2
  - debug:
      var: output
  - assert:
      that:
      # "output" contains the value of "input" at the time it has been defined
      - output == 'test1'