Ansible filter plugin

debug.log

$ ansible-playbook -i localhost, hoge.yml

PLAY [localhost] **************************************************************

TASK: [debug ] ****************************************************************
ok: [localhost] => {
    "var": {
        "dict_merged": {
            "foo": {
                "bar": 1,
                "baz": 2
            },
            "qux": 2
        }
    }
}

TASK: [debug ] ****************************************************************
ok: [localhost] => {
    "var": {
        "dict_update": {
            "foo": {
                "baz": 2
            },
            "qux": 2
        }
    }
}

PLAY RECAP ********************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0

dict_merge.py

# idea from here
# https://www.xormedia.com/recursively-merge-dictionaries-in-python/

from copy import deepcopy


def dict_merge(a, b):
    if not isinstance(b, dict):
        return b
    result = deepcopy(a)
    for k, v in b.iteritems():
        if k in result and isinstance(result[k], dict):
                result[k] = dict_merge(result[k], v)
        else:
            result[k] = deepcopy(v)
    return result


class FilterModule(object):
    def filters(self):
        return {'dict_merge': dict_merge}

test.yml

- hosts: localhost
  gather_facts: no
  vars:
    dict:
      foo:
        bar: 1
    dict2:
      foo:
        baz: 2
      qux: 2
    # custom filter plugin
    dict_merged: "{{ dict | dict_merge(dict2) }}"
    # jinja2 default update
    dict_update: |
      {% do dict.update(dict2) %}
      {{ dict }}
  tasks:
    - debug:
        var: dict_merged
    - debug:
        var: dict_update