Question

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 it fails to open the file.

Answer 1

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.

Answer 2

In case people like me stumble upon this question in 2022, Ansible now supports rescue blocks, which is similar to try-catch-finally in programming languages.

Examples can be found in the official documentation Error handling with blocks.

Answer 3

You can use block/rescue as follows:

- hosts: localhost
  tasks:
    - block:
        - debug: msg="{{ lookup( ini ,  foo section=DEFAULT file=missing-file.conf ) }}"
      rescue:
        - debug: msg="omit"

Answer 4

You can also convert your input file with a from_yaml filter before using the default filter

- name: "load a yaml file or a default value"
  set_fact:
    myvar: "{{ lookup( file ,  myfile.yml , errors= ignore ) | from_yaml | default(mydefaultObject, true) }}"

Answer 5

To avoid the error when the path doesn t exist, use a condition to check for the path before attempting the lookup:

---

- hosts: localhost
  tasks:

    - debug: msg="{{ lookup( ini ,  foo section=DEFAULT file=missing-file.conf ) }}"
      when: missing-file.conf | exists

You can use this with set_fact as well, then omit the undefined var when using it if required:

- hosts: localhost
  tasks:

    - set_fact:
        foo: "{{ lookup( ini ,  foo section=DEFAULT file=missing-file.conf ) }}"
      when: missing-file.conf | exists

    - debug:
        var: foo  # undefined
        msg: "{{ foo | default(omit) }}"  # omitted

Note that lookups and Jinja2 tests run on the controller. If you need to check the path on the host, use the stat and either slurp or fetch modules:

- stat:
    file: missing-remote-file-with-text-i-want
  register: file

- slurp:
    src: missing-remote-file-with-text-i-want
  register: slurp
  when: file.stat.exists

- set_fact:
    foo: "{{ slurp.content | b64decode }}"
  when: file.stat.exists

- fetch:
    src: missing-file.conf
    dest: /tmp/fetched
    fail_on_missing: False

- set_fact:
    bar: "{{ lookup( ini ,  foo section=DEFAULT file=/tmp/fetched/  + inventory_hostname +  /missing-file.conf ) }}"
  when: ( /tmp/fetched/  + inventory_hostname +  /missing-file.conf ) | exists

Second note, in Ansible v2.5 the grammar for using the path tests was changed, the format is now:

- set_fact:
    foo: "{{ lookup( ini ,  foo section=DEFAULT file=missing-file.conf ) }}"
  when:  "missing-file.conf" is exists

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