Merging two data structures with Ansible - merge

Question

Ansible v2.9.25
I'm trying to merge two data structures with Ansible. I'm almost there but I'm not able to merge all data.
Let me explain:
I want to merge main_roles together with default_roles:
main_roles:
- name: admin
role_ref: admin
subjects:
- name: test
kind: ServiceAccount
- name: test2
kind: ServiceAccount
- name: edit
role_ref: edit
subjects:
- name: test
kind: ServiceAccount
default_roles:
- name: edit
role_ref: edit
subjects:
- name: merge_me
kind: ServiceAccount
I'm successfully combining with the following task:
- name: "Setting var roles_managed"
set_fact:
roles_managed: "{{ roles_managed | default([]) + [ item | combine(default_roles|selectattr('name', 'match', item.name) |list)] }}"
loop: "{{ main_roles }}"
Printing the var via loop.
- name: "print all roles"
ansible.builtin.debug:
msg: "{{ item }}"
loop: "{{ roles_managed }}"
ok: [] => (item={u'subjects': [{u'kind': u'ServiceAccount', u'name': u'test'}, {u'kind': u'ServiceAccount', u'name': u'test2'}], u'name': u'admin', u'role_ref': u'admin'}) => {
"msg": {
"name": "admin",
"role_ref": "admin",
"subjects": [
{
"kind": "ServiceAccount",
"name": "test"
},
{
"kind": "ServiceAccount",
"name": "test2"
}
]
}
}
ok: [] => (item={u'subjects': [{u'kind': u'ServiceAccount', u'name': u'merge_me'}], u'name': u'edit', u'role_ref': u'edit'}) => {
"msg": {
"name": "edit",
"role_ref": "edit",
"subjects": [
{
"kind": "ServiceAccount",
"name": "merge_me"
}
]
}
}
This results in a combine on the item.name. But I want the result to be also a merge of the subjects. So i would need a end result of merge_me and test (the subjects under name:edit):
- name: edit
role_ref: edit
subjects:
- name: merge_me
kind: ServiceAccount
- name: test
kind: ServiceAccount
What I'm understanding Ansible is not merging recursively by default. So I would need to set recursive=true in the combine filter. See: Combining hashes/dictionaries
But I'm not able to set this successfully in my context.
When I try: {{ roles_managed | default([]) + [ item | combine(default_role_bindings, recursive=true|selectattr('name', 'match', item.name) |list)] }} for example I'm getting an 'bool' object is not iterable" error code...
I've tried many variations and searched many other posts. But I'm still unsuccessfully after probably too many hours ;). Hoping someone has a solution!

Answer 1

Both main_roles and default_roles are lists. It's not possible to combine lists. Instead, it's possible to add them and groupby name. Then combine the dictionaries with the same name, e.g.
- set_fact:
my_roles: "{{ my_roles|d([]) + [item.1|combine(list_merge='append')] }}"
loop: "{{ (main_roles + default_roles)|groupby('name') }}"
gives
my_roles:
- name: admin
role_ref: admin
subjects:
- kind: ServiceAccount
name: test
- kind: ServiceAccount
name: test2
- name: edit
role_ref: edit
subjects:
- kind: ServiceAccount
name: test
- kind: ServiceAccount
name: merge_me
Use list_merge='append', available since 2.10, to append the items of the lists.
Append the subjects on your own if the option append is not available in your version, e.g. the task below gives the same result
- set_fact:
my_roles: "{{ my_roles|d([]) + [item.1.0|combine({'subjects':_subj})] }}"
loop: "{{ (main_roles + default_roles)|groupby('name') }}"
vars:
_subj: "{{ item.1|map(attribute='subjects')|flatten }}"