Force Ansible to throw out error when vars is missing in yml?

Question

Is it possible to force Ansible when replacing the var in yml files, which is undefined, throw out an error instead silently replaced by an empty string?

Answer 1

Yes, it is possible. Check the online documentation, under accessing complex variable data.

An example is provided to do exactly that:

tasks:
    - shell: echo "I've got '{{ foo }}' and am not afraid to use it!"
      when: foo is defined

    - fail: msg="Bailing out: this play requires 'bar'"
      when: bar is not defined

Answer 2

Add this line to the [defaults] section of your ansible.cfg:

error_on_undefined_vars = True

You'll now get an error message if a variable is undefined.

Answer 3

You can use mandatory-values

If you configure Ansible to ignore undefined variables, you may want to define some values as mandatory. By default, Ansible fails if a variable in your playbook or command is undefined. You can configure Ansible to allow undefined variables by setting DEFAULT_UNDEFINED_VAR_BEHAVIOR to false. In that case, you may want to require some variables to be defined. You can do this with:

{{ variable | mandatory }}

Answer 4

Define your variables in

roles/<role_name>/defaults/main.yml

like:

SUPERVAR:
  VAR1:foo
  VAR2:bar

and then do in

roles/<role_name>/tasks/main.yml

like:

- fail: msg="{{ item }} is not defined"
  when: not {{ item }}
  with_items:
    - SUPERVAR.VAR1
    - SUPERVAR.VAR2