Default value for `hosts: {{ host }}` substitution doesn't work

[anatoly techtonik]

I try to set default value for hosts field in playbook with Jinja2 filter, but it doesn't work:

---
- hosts: "{{ host | default(localhost) }}"
  tasks:
  - name: show OS version info
    debug: msg="{{ansible_distribution}} {{ansible_distribution_version}}"

# ansible-playbook -i hosts dist.yml

PLAY [{{host | default(localhost)}}] ******************************************

skipping: no hosts matched

But when I execute it with command line parameter, it works ok:

# ansible-playbook -i hosts dist.yml --extra-vars 'host=localhost'

PLAY [localhost] **************************************************************

...

??? 

[Scott Sturdivant]

Change to default('localhost').

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[anatoly techtonik]

Found the reason myself:

---
- hosts: "{{ host | default(localhost) }}"

This should be:

--- 

- hosts: "{{ host | default('localhost') }}"

Still would be nice to get more valuable error message. I guess Jinja2 translates bare localhost to variable name, which in turn is translated to empty string, but why the Ansible shows PLAY [{{host | default(localhost)}}] **** and not PLAY [] **** or PLAY [#ERROR] **** ?

[anatoly techtonik]

@Scott, thanks. Trial and error told me that way too.

[Michael DeHaan]

If you are attempting to drive the host spec based on inventory variables, this won't work.

If you drive it with input from -e, it will.

You can't use inventory variables to drive the host spec.

[anatoly techtonik]

On Friday, February 21, 2014 11:59:28 PM UTC+3, Michael DeHaan wrote:

If you are attempting to drive the host spec based on inventory variables, this won't work.

If you drive it with input from -e, it will.

You can't use inventory variables to drive the host spec.

Why? Isn't the initialization order sets inventory variables first?

[Michael DeHaan]

This is documented here:

http://docs.ansible.com/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable

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