How to use the lookup plugin to get the directory path and file in Ansible - ansible

Question

I have a two playbooks where one creates SSH Keys and the other one creates a new user and deploys the public ssh key for the new user created.
My issue is I created a task that create a new directory with a timestamp to store the relevant data, I was able to get the path to a variable where I added it as a dummy host so that I can be able to call that path with all my plays but it seems like I am unable to use the same variable in lookup so that I can be able to deploy the ssh key. Kindly assist, below are the relevant tasks.
# Create the directory with timestamp
- name: Create Directory with timestamp to store data that was run multiple times that day
when: inventory_hostname in groups['local']
file:
path: "{{store_files_path}}/{{ansible_date_time.date}}/{{ansible_date_time.time}}"
state: directory
mode: "0755"
register: dir_path
# Add the directory path to dummy host called save so that I can call it from other plays
- name: Add dir path:"{{dir_path.path}}" as a 'save' host
when: inventory_hostname in groups['local']
add_host:
name: "save"
dir: "{{dir_path.path}}"
# Deploying SSH Key I tried this -->
- name: Deploy Public Key to the server
when: inventory_hostname in groups['Servers']
authorized_key:
user: "{{hostvars['new-user']['user']}}"
state: present
key: "{{dir_path.path}}/SSH-Key.pub"
# ...this -->
- name: Deploy Public Key to the server
when: inventory_hostname in groups['Servers']
authorized_key:
user: "{{hostvars['new-user']['user']}}"
state: present
key: "{{ lookup('file','{{dir_path.path}}/SSH-Key.pub') }}"
# .... and this -->
- name: Deploy Public Key to the server
when: inventory_hostname in groups['Servers']
authorized_key:
user: "{{hostvars['new-user']['user']}}"
state: present
key: "{{ lookup('file','{{hostvars['save']['dir']}}/SSH-Key.pub') }}"
None of them worked, what am I doing wrong?

Answer 1

If you put a Jinja expression into a string in a Jinja expression, then you indeed end up with a your variable not being interpreted.
A basic example of this is:
- hosts: all
gather_facts: no
tasks:
- debug:
msg: "{{ '{{ foo }}' }}"
vars:
foo: bar
Which gives:
ok: [localhost] => {
"msg": "{{ foo }}"
}
When
- hosts: all
gather_facts: no
tasks:
- debug:
msg: "{{ foo }}"
vars:
foo: bar
Gives thes expected:
ok: [localhost] => {
"msg": "bar"
}
So in order to achieve what you want here, you should use the concatenation operator of Jinja: ~, in order to let Jinja interpret your variable and concatenate it with the rest of your "hardcoded" string.
Effectively ending with the instruction:
key: "{{ lookup('file', hostvars['save']['dir'] ~ '/SSH-Key.pub') }}"