How to concatenate two lists of dictonaries in Ansible - list

Question

I have two list of dicts:
dev_users:
- name: cs3141
key:
cs513e_key1.pub
cs513e_key2.pub
- name: ab1234
key:
ab1234.pub
- name: cd5678
key:
ab1234.pub
and
sys_admin_users:
- name: xy3141
key:
xy3141.pub
- name: cd1234
key:
cd1234.pub
- name: ef5678
key:
ef5678.pub
When I try to concatenate them:
- set_fact: users= "{{ dev_users + sys_admin_users }}"
I get this error:
ERROR! failed to combine variables, expected dicts but got a 'dict' and a 'AnsibleSequence':
{}
[{"set_fact": "users= \"{{ dev_users + sys_admin_users }}\""}]
How can I concatenate these two lists?

Answer 1

The problem was that I was trying to concatenate the two list in the variables section, as opposed to the task section. Tadeboro in #ansible gave me this code that worked:
---
- hosts: localhost
gather_facts: false
vars:
dev_users:
- name: cs3141
key:
cs513e_key1.pub
cs513e_key2.pub
- name: ab1234
key:
ab1234.pub
- name: cd5678
key:
ab1234.pub
sys_admin_users:
- name: xy3141
key:
xy3141.pub
- name: cd1234
key:
cd1234.pub
- name: ef5678
key:
ef5678.pub
tasks:
- name: Test
set_fact:
users: "{{ dev_users + sys_admin_users }}"
This command works fine: ansible-playbook -v x.yaml

Answer 2

Here is another solution, that iteratively concatenates a list of list. I like it better, because it is more general. It only works in more recent versions of ansible, because there was a bug in version 2.5 which took some time to fix.
---
# ansible-playbook -v manyx.yaml
- hosts: localhost
gather_facts: false
vars:
dev_users:
- name: cs3141
key:
cs513e_key1.pub
cs513e_key2.pub
- name: ab1234
key:
ab1234.pub
- name: cd5678
key:
ab1234.pub
sys_admin_users:
- name: xy3141
key:
xy3141.pub
- name: cd1234
key:
cd1234.pub
- name: ef5678
key:
ef5678.pub
other_users:
- name: fe9876
key:
fe9876.pub
list_of_users_list:
- "{{ dev_users }}"
- "{{ sys_admin_users }}"
- "{{ other_users }}"
all_users: []
tasks:
- name: Test
set_fact:
all_users: "{{ item + all_users }}"
loop: "{{ list_of_users_list }}"
- name: print all_users
debug:
msg: "{{ item }}"
loop: "{{ all_users }}"