Variables inside JSON Query - Ansible / Jinja filter

I am trying to use JSON query to dynamically generate lists

The state of the variables is:

fabric:
  vrfs:
    - name: VRF-A 
      description: Production-Network
      id: 10001
      vlan: 2002
      switches:
        - serial_number: 10.122.18.114
        - serial_number: 10.122.18.118
    - name: VRF-F
      description: Production-Network
      id: 10001
      vlan: 2022
      switches:
        - serial_number: 10.122.18.114
        - serial_number: 10.122.18.118

I want to get the switches in the VRF-A using a JSON query. When the JSON query is hardcoded it works.

  - name: JSON Query
    set_fact:
      switches: "{{ fabric |json_query('vrfs[?(@.name==`VRF-A`)].switches') }}"

But when I use variables, Ansible returns an empty List

  - name: JSON Query
    set_fact:
      switches: "{{ fabric |json_query('vrfs[?(@.name==`{{ the_vrf }}`)].switches') }}"

Am I missing something? Is there any workaround for this?

Ansible doesn't support the nested expansion of variables. You can put the query into a separate variable (see the note on the one-liner)

  the_vrf: VRF-A
  switches_query: '[?name == `{{ the_vrf }}`].switches'
  switches: "{{ fabric.vrfs|json_query(switches_query) }}"

give what you want

  switches:
  - - serial_number: 10.122.18.114
    - serial_number: 10.122.18.118

<hr>

Notes:

• The query from your example can be simplified. Both options below give the same result

  switches: "{{ fabric.vrfs|json_query('[?name == `VRF-A`].switches') }}"

  switches_query: '[?name == `VRF-A`].switches'
  switches: "{{ fabric.vrfs|json_query(swiches_query) }}"

• The query string can be concatenated

 switches_query: "{{ '[?name == `' ~ the_vrf ~ '`].switches' }}"

gives the same query (test it in the example playbook)

  switches_query: '[?name == `VRF-A`].switches'

It seems this string might be used in the one-liner

  switches: "{{ fabric.vrms|json_query('[?name == `' ~ the_vrf ~ '`].switches') }}"

Unfortunately, this doesn't work and I'm not able to figure out what escaping might be needed, if possible. (Comments on this are more than welcome.) The result of this one-liner is

  switches: ''

• Example of a complete playbook for testing

<sup>

- hosts: localhost

  vars:

    fabric:
      vrfs:
        - name: VRF-A 
          description: Production-Network
          id: 10001
          vlan: 2002
          switches:
            - serial_number: 10.122.18.114
            - serial_number: 10.122.18.118
        - name: VRF-F
          description: Production-Network
          id: 10001
          vlan: 2022
          switches:
            - serial_number: 10.122.18.114
            - serial_number: 10.122.18.118

    # switches: "{{ fabric.vrfs|json_query('[?name == `VRF-A`].switches') }}"
    # switches_query: '[?name == `VRF-A`].switches'
    # switches: "{{ fabric.vrfs|json_query(swiches_query) }}"

    the_vrf: VRF-A
    # switches_query: "{{ '[?name == `' ~ the_vrf ~ '`].switches' }}"
    switches_query: '[?name == `{{ the_vrf }}`].switches'

    # switches: "{{ fabric.vrms|json_query('[?name == `' ~ the_vrf ~ '`].switches') }}"
    switches: "{{ fabric.vrfs|json_query(switches_query) }}"

  tasks:

    - debug:
        var: switches_query
    - debug:
        var: switches

</sup>