Exclude AnsibleUndefined from a list - ansible

Question

Relevant part of task:
- name: Get join-token for worker nodes
set_fact:
join_token_worker: "{{ ansible_play_hosts_all | map('extract', hostvars, ['result', 'swarm_facts', 'JoinTokens', 'Worker']) }}"
run_once: true
- debug:
msg: "{{ join_token_worker }}"
run_once: true
And the output looks like this:
TASK [deploy_docker : Get join-token for worker nodes] ********************************************************************************************************************************************************************************************************************************************************
ok: [eu-central-1a-01]
TASK [deploy_docker : debug] **********************************************************************************************************************************************************************************************************************************************************************************
ok: [eu-central-1a-01] => {
"msg": "[AnsibleUndefined, AnsibleUndefined, AnsibleUndefined, 'SWMTKN-1-2xgm1l987hh18gbq0tc8vrwn209qlxge6nkwdq4pof2zd4e2vs-7f7ig2ama5amqq8iuii4o8xxo', AnsibleUndefined, AnsibleUndefined, 'SWMTKN-1-2xgm1l987hh18gbq0tc8vrwn209qlxge6nkwdq4pof2zd4e2vs-7f7ig2ama5amqq8iuii4o8xxo', AnsibleUndefined, AnsibleUndefined]"
}
I want to extract the token from this list - but I don't know how to filter out AnsibleUndefined value. I am using docker_swarm module to get result.

Answer 1

Let's minimize the case. For example, the playbook
- hosts: h1,h2,h3
gather_facts: false
vars:
d2:
h1:
k1:
k2: v1
h2:
k1:
kX: v2
h3:
k1:
k2: v3
tasks:
- debug:
msg: "{{ ansible_play_hosts_all|
map('extract', d2, ['k1', 'k2'])|
list }}"
run_once: true
gives
msg: '[''v1'', Undefined, ''v3'']'
There are more options for how to "Exclude AnsibleUndefined from a list".
Use select (credit #mdaniel)
- debug:
msg: "{{ ansible_play_hosts_all|
map('extract', d2, ['k1', 'k2'])|
select|
list }}"
run_once: true
gives
msg:
- v1
- v3
Use regex_replace
- debug:
msg: "{{ ansible_play_hosts_all|
map('extract', d2, ['k1', 'k2'])|
map('regex_replace', '(.*)', '\\1')|
list }}"
run_once: true
gives
msg:
- v1
- ''
- v3
If you want to create a dictionary iterate the hosts. For example
- set_fact:
worker_dict: "{{ worker_dict|default({})|
combine({item: d2[item].k1.k2|default('')}) }}"
loop: "{{ ansible_play_hosts_all }}"
run_once: true
gives
worker_dict:
h1: v1
h2: ''
h3: v3