How to fallback to a default value when ansible lookup fails?

I was a little bit surprised to discover that his piece of code fails with an IOError exception instead of defaulting to omitting the value.

#!/usr/bin/env ansible-playbook -i localhost,
---
- hosts: localhost
  tasks:
    - debug: msg="{{ lookup('ini', 'foo section=DEFAULT file=missing-file.conf') | default(omit) }}"

How can I load a value without raising an exception?

Please note that the lookup module supports a default value parameter but this one is useless to me because it works only when it can open the file.

I need a default value that works even when the lookup fails to open the file.

Solution

As far as I know Jinja2 unfortunately doesn't support any try/catch mechanism.

So you either patch ini lookup plugin / file issue to Ansible team, or use this ugly workaround:

---
- hosts: localhost
  gather_facts: no
  tasks:
    - debug: msg="{{ lookup('first_found', dict(files=['test-ini.conf'], skip=true)) | ternary(lookup('ini', 'foo section=DEFAULT file=test-ini.conf'), omit) }}"

In this example first_found lookup return file name if file exists or empty list otherwise. If file exists, ternary filter calls ini lookup, otherwise omit placeholder is returned.