How to nicely split on multiple lines long conditionals with OR on ansible?

Question

I already know that if you have long conditionals with and between them you can use lists to split them on multiple lines.

Still, I am not aware of any solution for the case where you have OR between them.

Practical example from real life:

when: ansible_user_dir is not defined or ansible_python is not defined or ansible_processor_vcpus is not defined

This line is ugly and hard to read, and clearly would not fit a 79 column.

How can we rewrite it to make it easier to read?

Answer 1

Use the YAML folding operator >

when: >
  ansible_user_dir is not defined or
  ansible_python is not defined or
  ansible_processor_vcpus is not defined

As the ansible documentation states:

Values can span multiple lines using | or >. Spanning multiple lines using a Literal Block Scalar | will include the newlines and any trailing spaces. Using a Folded Block Scalar > will fold newlines to spaces; it’s used to make what would otherwise be a very long line easier to read and edit. In either case the indentation will be ignored.

Additional info can be found here:

• https://yaml-multiline.info/
• https://docs.ansible.com/ansible/latest/reference_appendices/YAMLSyntax.html
• http://yaml.org/spec/1.2/spec.html#id2760844

Answer 2

While you should use yaml operators and syntax for majority of the Ansible code, you don't have to use yaml operators with when: conditional. Take a look at official docs. When conditional can be really flexible depends on your need. I think it works because when conditionals are already an expression and evaluated by Jinja2 directly, hence you don't use {{ }} in when condition.

Another great reference: https://stackoverflow.com/a/57600771/9720375

---
- name: Test multiline when condition
  hosts: all
  gather_facts: false
  strategy: linear
  tasks:
    - name: Should run
      debug:
        msg: "print this if works"
      when:
        - true
        - false or
          true

    - name: Should run
      debug:
        msg: "print this if works"
      when:
        - true
        - true or
          false

    - name: Should run
      debug:
        msg: "print this if works"
      when:
        - false or true

    - name: Should skip
      debug:
        msg: "print this if works"
      when:
        - false
        - false or true

    - name: Should run
      debug:
        msg: "print this if works"
      when:
        false or true

    - name: Should skip
      debug:
        msg: "print this if works"
      when:
        false or
        false

    - name: Should run
      debug:
        msg: "print this if works"
      when: (false or true) or (false and true)

    - name: Should run
      debug:
        msg: "print this if works"
      when: (false or false) or
            (true and true)