How can I keep keys in Ansible non recursively?

I want to remove some keys (nesting level 0) from a list of dictionnaries so that I can apply the unique filter and get some sort of classification of my list items. If I use the ansible.utils.keep_keys filter, I get undesired results, because it only works recursively. This may result in kept unmatched keys on nesting level 0 if some subkey matches the filter. Further more, this filter behaves strangely if lists of integers are involved, e. g.:

- debug:
    msg: "{{ my_list | keep_keys(target=['key0', 'key1']) | unique }}"
  vars:
    my_list:
      - key0: A
        key1: B
        key2:
          - 1
        key3: foo
      - key0: A
        key1: B
        key2:
          - 2
        key4: bar

results in:

msg:
  - key0: A
    key1: B
    key2:
    - 1
  - key0: A
    key1: B
    key2:
    - 2

instead of:

msg:
  - key0: A
    key1: B

remove_keys is not an option, because it also works recursively and the number of unwanted keys is way bigger than the number of desired keys. As keep_keys does not offer an option to work non recursively, I assume there must be another way to achieve this, but I cannot figure it out.

Is there a way to keep keys in Ansible non recursively, besides developing my own filter?

Solution

Use Jinja. For example,

  keep: [key0, key1]
  result: |
    {% filter from_yaml %}
    {% for i in my_list %}
    - {{ dict(keep|zip(keep|map('extract', i))) }}
    {% endfor %}
    {% endfilter %}

gives

  result:
    - {key0: A, key1: B}
    - {key0: A, key1: B}

^{Example of a complete playbook for testing
- hosts: localhost

vars:

my_list:
- key0: A
key1: B
key2: [1]
key3: foo
- key0: A
key1: B
key2: [2]
key4: bar

keep: [key0, key1]
result: |
{% filter from_yaml %}
{% for i in my_list %}
- {{ dict(keep|zip(keep|map('extract', i))) }}
{% endfor %}
{% endfilter %}

tasks:

- debug:
var: result|to_yaml
- debug:
var: result|unique}