Flatten doubly-nested Ansible dict

Question

How would I get from sessions to sessions_flat in a call to set_fact within Ansible?

sessions:
  - name: "clientALPHA"
    vpns:
      - name: "tun10"
        password: 56813252
        port: 1194
      - name: "tun20"
        password: 90871307
        port: 1195
  - name: "clientBRAVO"
    vpns:
      - name: "tun10"
        password: 76530913
        port: 1196


sessions_flat:
  - oid: "clientALPHA-tun10"
    password: 56813252
    port: 1194
  - oid: "clientALPHA-tun20"
    password: 90871307
    port: 1195
  - oid: "clientBRAVO-tun10"
    password: 76530913
    port: 1196

Answer 1

You could use a loop with the subelements filter, like this:

- set_fact:
    sessions_flat: >-
      {{
        sessions_flat + [{
          "port": item.1.port,
          "password": item.1.password
        }|combine({"oid": "%s-%s" % (item.0.name, item.1.name)})]
      }}
  vars:
    sessions_flat: []
  loop: "{{ sessions|subelements('vpns')}}"

If you're using the community edition of jmespath, you could use a let expression:

- set_fact:
    sessions_flat: >-
      {{
      sessions | json_query('[].[let $top = @ in $top.vpns[]|[].{"oid": join(`"-"`, [$top.name, name]), "port": port, "password": password}][][]')
      }}

Both of the above tasks result in:

{
  "sessions_flat": [
      {
          "oid": "clientALPHA-tun10",
          "password": 56813252,
          "port": 1194
      },
      {
          "oid": "clientALPHA-tun20",
          "password": 90871307,
          "port": 1195
      },
      {
          "oid": "clientBRAVO-tun10",
          "password": 76530913,
          "port": 1196
      }
  ]
}