Ansible: variable interpolation in task name - ansible

Question

I cannot get this seemingly simple example to work in Ansible 1.8.3. The variable interpolation does not kick in the task name. All examples I have seen seem to suggest this should work. Given that the variable is defined in the vars section I expected the task name to print the value of the variable. Why doesn't this work?
Even the example from the Ansible documentation seems to not print the variable value.
---
- hosts: 127.0.0.1
gather_facts: no
vars:
vhost: "foo"
tasks:
- name: create a virtual host file for {{ vhost }}
debug: msg="{{ vhost }}"
This results in the following output:
PLAY [127.0.0.1]
**************************************************************
TASK: [create a virtual host file for {{ vhost }}]
****************************
ok: [127.0.0.1] => {
"msg": "foo"
}
PLAY RECAP
********************************************************************
127.0.0.1 : ok=1 changed=0 unreachable=0 failed=0
Update
This works with 1.7.2 but does not work with 1.8.3. So either this is a bug or a feature.

Answer 1

Variables are not resolved inside the name. Only inside the actual tasks/conditions etc. the placeholders will be resolved. I guess this is by design. Imagine you have a with_items loop and use the {{ item }}in the name. The tasks name will only be printed once, but the {{ item }} would change in every iteration.
I see the examples, even the one in the doc you linked to, use variables in the name. But that doesn't mean the result would be like you expected it. The docs are community managed. It might be someone just put that line there w/o testing it - or maybe it used to work like that in a previous version of Ansible and the docs have not been updated then. (I'm only using Ansible since about one year). But even though it doesn't work like we wish it would, I'm still using variables in my name's, just to indicate that the task is based on dynamic parameters. Might be the examples have been written with the same intention.
An interesting observation I recently made (Ansible 1.9.4) is, default values are written out in the task name.
- name: create a virtual host file for {{ vhost | default("foo") }}
When executed, Ansible would show the task title as:
TASK: [create a virtual host file for foo]
This way you can avoid ugly task names in the output.

Answer 2

Explanation
Whether the variable gets interpolated depends on where it has been declared.
Imagine You have two hosts: A and B.
If variable foo has only per-host values, when Ansible runs the play, it cannot decide which value to use.
On the other hand, if it has a global value (global in a sense of host invariance), there is no confusion which value to use.
Source: https://github.com/ansible/ansible/issues/3103#issuecomment-18835432
Hands on playbook
ansible_user is an inventory variable
greeting is an invariant variable
- name: Test variable substitution in names
hosts: localhost
connection: local
vars:
greeting: Hello
tasks:
- name: Sorry {{ ansible_user }}
debug:
msg: this won't work
- name: You say '{{ greeting }}'
debug:
var: ansible_user

Answer 3

I experienced the same problem today in one of my Ansible roles and I noticed something interesting.
When I use the set_fact module before I use the vars in the task name, they actually get translated to their correct values.
In this example I wanted to set the password for a remote user:
Notice that I use the vars test_user and user_password that I set as facts before.
- name: Prepare to set user password
set_fact:
user_password: "{{ linux_pass }}"
user_salt: "s0m3s4lt"
test_user: "{{ ansible_user }}"
- name: "Changing password for user {{ test_user }} to {{ user_password }}"
user:
name: "{{ ansible_user }}"
password: "{{ user_password | password_hash('sha512', user_salt) }}"
state: present
shell: /bin/bash
update_password: always
This gives me the following output:
TASK [install : Changing password for user linux to LiNuXuSeRPaSs#]
So this solved my problem.

Answer 4

It might be ugly, but you can somewhat workaround with something like this:
- name: create a virtual host file
debug:
msg: "Some command result"
loop: "{{ [ vhost ] }}"
or
- name: create a virtual host file
debug:
msg: "Some command result"
loop_control:
label: "{{ vhost }}"
loop: [1]
I wouldn't do this in general, but it shows how you can use items or label to give information outside of the command result. While it might not
Source: https://docs.ansible.com/ansible/latest/user_guide/playbooks_loops.html