Merge 2 lists of dictionaries by property value in Ansible - ansible

Question

I'm trying to merge 2 lists of dictionary objects by one of the properties, but I can't seem to find the correct syntax/filters to do so
default_settings:
- { name: 'setting1', value: 'default value1' }
- { name: 'setting2', value: 'default value2' }
overrides:
- { name: 'setting1', value: 'overridden value' }
- { name: 'setting3', value: 'new value3' }
This should result in:
result:
- { name: 'setting1', value: 'overridden value' }
- { name: 'setting2', value: 'default value2' }
- { name: 'setting3', value: 'new value3' }
I've tried my luck with simply adding them, using combine filter, but those things either only work on dictionaries or lists, but not lists of dictionaries.

Answer 1

Of course after 2 hours of trying and searching and eventually making this post, I managed to get it working in a final little thing I tested. So for those who have the same problem, you can use the groupby filter, combined with a mapped last and mapped combine.
---
- hosts: localhost
connection: local
gather_facts: no
vars:
default_settings:
- { name: 'setting1', value: 'default value1' }
- { name: 'setting2', value: 'default value2' }
overrides:
- { name: 'setting1', value: 'overridden value' }
- { name: 'setting3', value: 'new value3' }
tasks:
- debug:
msg: "{{ item.name }} = {{ item.value }}"
loop: "{{ (default_settings + overrides) | groupby('name') | map('last') | map('combine') }}"
TASK [debug] *********************************************************************************************************************************************************************************************************************************************************************
ok: [localhost] => (item={'name': 'setting1', 'value': 'overridden value'}) => {
"msg": "setting1 = overridden value"
}
ok: [localhost] => (item={'name': 'setting2', 'value': 'default value2'}) => {
"msg": "setting2 = default value2"
}
ok: [localhost] => (item={'name': 'setting3', 'value': 'new value3'}) => {
"msg": "setting3 = new value3"
}

Answer 2

The easiest way is to convert them to dictionaries and combine them:
- hosts: localhost
gather_facts: no
vars:
default_settings:
- { name: 'setting1', value: 'default value1' }
- { name: 'setting2', value: 'default value2' }
overrides:
- { name: 'setting1', value: 'overridden value' }
- { name: 'setting3', value: 'new value3' }
combined_settings: "{{ [default_settings, overrides] | map('items2dict', key_name='name') | combine }}"
tasks:
- name: now you have a dict
debug:
msg: "{{ combined_settings }}"
- name: which you can convert back to a list to iterate over
debug:
msg: "{{ item.key }}: {{ item.value }}"
loop: "{{ combined_settings | dict2items }}"
TASK [now you have a dict] ********************************************************
ok: [localhost] => {
"msg": {
"setting1": "overridden value",
"setting2": "default value2",
"setting3": "new value3"
}
}
TASK [which you can convert back to a list to iterate over] ***********************
ok: [localhost] => (item={'key': 'setting1', 'value': 'overridden value'}) => {
"msg": "setting1: overridden value"
}
ok: [localhost] => (item={'key': 'setting2', 'value': 'default value2'}) => {
"msg": "setting2: default value2"
}
ok: [localhost] => (item={'key': 'setting3', 'value': 'new value3'}) => {
"msg": "setting3: new value3"
}