Ansible - remove empty elements from the list - list

Question

I have an ansible output from which I want to remove all empty (none) elements for a specific attribute. Here is the example list:
"resources": [
{
"id": "9c40900909",
"name": "some_name1"
},
{
"id": "pc4b09090"
},
{
"id": "8lknkkn45"
},
{
"id": "9df40900909",
"name": "some_name2"
}
]
Here is how I reduced the list to be just "resources" with attribute "name":
- set_fact:
resources_names: "{{ output.resources | map(attribute='name') }}"
Problem with that is that I get the elements that does not have any value for the name. These are "AnsibleUndefined" in the following output:
- debug:
msg: resources_names list is "{{ resources_names }}"
ok: [localhost] => {
"msg": "resources_names list is \"['some_name1', AnsibleUndefined, AnsibleUndefined, 'some_name2']\""
}
I tried to remove it with reject and regexp but that's not working.
- set_fact:
list2: "{{ resources_names | reject('match', '^$') | list }}"
Same with this one:
- set_fact:
resources_names: "{{ output.resources | map(attribute='name') | rejectattr('name', 'none') }}"
Any idea?
Thanks.

Answer 1

In a nutshell:
---
- hosts: localhost
gather_facts: false
vars:
resources: [
{
"id": "9c40900909",
"name": "some_name1"
},
{
"id": "pc4b09090"
},
{
"id": "8lknkkn45"
},
{
"id": "9df40900909",
"name": "some_name2"
}
]
tasks:
- debug:
msg: "{{ resources | selectattr('name', 'defined') | map(attribute='name') }}"
which gives:
$ ansible-playbook /tmp/play.yml
[WARNING]: No inventory was parsed, only implicit localhost is available
PLAY [localhost] *******************************************************************************************************************************************************************************
TASK [debug] ***********************************************************************************************************************************************************************************
ok: [localhost] => {
"msg": [
"some_name1",
"some_name2"
]
}
PLAY RECAP *************************************************************************************************************************************************************************************
localhost : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Note for your next question: please make sure you double check your examples and paste valid json/yaml data in your question. Thanks

Answer 2

Use the filter json_query. This filter ignores missing attributes
resources_names: "{{ output.resources|json_query('[].name') }}"
gives
resources_names:
- some_name1
- some_name2