I have this piece of code that checks if the variable "owner" matches with the following regex and accepts that it is undefined, that is, the playbook can work without that variable being passed.
varexample is undefined or varexample is match('^[a-zA-Z]+$')
What I would like to do is that this variable accepts empty or null values. What I tried is something like this
varexample is null or varexample is match('^[a-zA-Z]+$')
But I got this error:
The conditional check 'varexample is null or varexample is match('[a-zA-Z]+')' failed. The error was: template error while templating string: no test named 'null'. String: {% if varexample is null or varexample is match('[a-zA-Z]+') %} True {% else %} False {% endif %}
Can someone give me a hint or some help?
Q: "variable accepts null values"
A: It's a bug. Ansible shouldn't match null to '^[a-zA-Z]+$'
- set_fact:
varexample:
- debug:
var: varexample
- debug:
msg: "undefined: {{ varexample is undefined }}"
- debug:
msg: "match: {{ varexample is match('^[a-zA-Z]+$') }}"
gives
varexample: null
msg: 'undefined: False'
msg: 'match: True'
As a result of this bug, your condition should be working as expected
varexample is undefined or varexample is match('^[a-zA-Z]+$')
To be on the save side, for the case the bug will be fixed, you can additionally test None, e.g.
- debug:
msg: "Test passed. varexample: {{ item.varexample }}"
when: item.varexample is undefined or
item.varexample == None or
item.varexample is match('^[a-zA-Z]+$')
loop:
- varexample: ABC
- varexample: 123
- varexample:
gives
ok: [localhost] => (item={'varexample': 'ABC'}) =>
msg: 'Test passed. varexample: ABC'
skipping: [localhost] => (item={'varexample': 123})
ok: [localhost] => (item={'varexample': None}) =>
msg: 'Test passed. varexample: '
Details
- debug:
msg: |
Undefined: {{ item.varexample is undefined }}
Is None: {{ item.varexample == None }}
Match a-zA-Z: {{ item.varexample is match('^[a-zA-Z]+$') }}
loop:
- varexample: ABC
- varexample: 123
- varexample:
ok: [localhost] => (item={'varexample': 'ABC'}) =>
msg: |-
Undefined: False
Is None: False
Match a-zA-Z: True
ok: [localhost] => (item={'varexample': 123}) =>
msg: |-
Undefined: False
Is None: False
Match a-zA-Z: False
ok: [localhost] => (item={'varexample': None}) =>
msg: |-
Undefined: False
Is None: True
Match a-zA-Z: True
Simply use a default that your match would consider truthy.
For example; with a varexample | default('a') is match('^[a-zA-Z]+$'), you should be able to achieve what you are looking for.
Given the tasks:
- debug:
msg: "for {{ item }} the result is {{ item | default('a') is match('[a-zA-Z]+') }}"
loop: "{{ cases }}"
vars:
cases:
- ~
- 123
- abc
-
- debug:
msg: "for an undefined variable the result is {{ item | default('a') is match('[a-zA-Z]+') }}"
This yields:
TASK [debug] ****************************************************************************
ok: [localhost] => (item=None) =>
msg: for the result is True
ok: [localhost] => (item=123) =>
msg: for 123 the result is False
ok: [localhost] => (item=abc) =>
msg: for abc the result is True
ok: [localhost] => (item=None) =>
msg: for the result is True
TASK [debug] ****************************************************************************
ok: [localhost] =>
msg: for an undefined variable the result is True
I think the closest answer to exactly what you asked for is something like:
varexample is defined and varexample is match('^[a-zA-Z]+$')
You can also use "is not defined", or just providing a default like mentioned in the other answer is another good way to go.
varexample|default('') is match('^[a-zA-Z]+$')