Why is ansible loop adding square brackets ("[]") into my role?

Question

I'm writing a role where I need to iterate over a list using the loop option. I'm using the ZFS module aisbergg.zfs.

The role:

    - hosts: localhost
      vars:
        zfs_pool_name: tank
        zfs_first_fs: subtank
        zfs_clients: 
          - mom
        clients_fs_size: 1T

      tasks:
        - name: Create the clusters's filesystem
          zfs:
            name: "{{ zfs_pool_name }}/{{ zfs_first_fs }}/{{ zfs_clients }}"
            state: present
            extra_zfs_properties:
              volsize: "{{ clients_fs_size }}"
          loop: "{{ zfs_clients }}"
          loop_control:
            pause: 5

When I run the playbook I got the following error:

TASK [Create the clusters's filesystem] ********************************************************************************************************************** failed: [localhost] (item=mom) => {"ansible_loop_var": "item", "changed": false, "item": "mom", "msg": "cannot create 'tank/subtank/[mom]': invalid character '[' in name\n"}

Meaning that somehow the square brackets sneak into my variable, which I got from a list.

Any idea on how can I get my variable without the square brackets?

Answer 1

Meaning that somehow the square brackets sneak into my variable, which I got from a list.

Right, that

cannot create 'tank/subtank/[mom]': invalid character '[' in name

is the expected behavior according the code snippet you've provided.

Any idea on how can I get my variable without the square brackets?

To get the list element in your loop you need just to reference it via item.

- name: Create the clusters's filesystem
  zfs:
    name: "{{ zfs_pool_name }}/{{ zfs_first_fs }}/{{ item }}"
    state: present
    extra_zfs_properties:
      volsize: "{{ clients_fs_size }}"
  loop: "{{ zfs_clients }}"
  loop_control:
    pause: 5

A minimal example which shows it more focused

- name: Loop over sample list
  debug:
    msg: "{{ item }}"
  loop: ['A', '1', 'B', '2']
  loop_control:
    extended: true
    label: "{{ ansible_loop.index0 }}"

will result into an output of

TASK [Loop over sample list] ******
ok: [localhost] => (item=0) =>
  msg: A
ok: [localhost] => (item=1) =>
  msg: '1'
ok: [localhost] => (item=2) =>
  msg: B
ok: [localhost] => (item=3) =>
  msg: '2'

Further Documentation

• Iterating over a simple list
• In Python, when to use a Dictionary, List or Set?, for some background information