Using a variable inside an Ansible loop

I am trying to get data from json data (below) using a loop with a variable (instead of hard coding a value). In the json data (below), 'cluster' can change therefore I cannot simply use: loop: "{{ drs_rule_jsondata.drs_rule_info.cluster }}" -- which works as I expect it would and produces the expected results.

However, when I use the play below (using vars in the loop and when {{ cluster_info.name }} = cluster), I get "msg": "'dict object' has no attribute 'drs_rule_jsondata.drs_rule_info.cluster'". The confusing part is, it produces the same syntax as the one that works.... should using vars this way in the loop not work? Is there another way to get the expected results given the 'cluster' can change?

Play:

- name: Set drs rule info
  set_fact:
    drs_rule: "{{ drs_rule|default([]) + [ {
      'rule_name': item | json_query('rule_name'),
      'rule_affinity': item | json_query('rule_affinity'),
      'rule_vms': item | json_query('rule_vms[*]')
      } ] }}"
  vars:
    path: drs_rule_jsondata.drs_rule_info
    cluster_name: "{{ cluster_info.name }}"
  loop: "{{ vars[path + '.' + cluster_name] }}"

json data:

{
  "ansible_facts": {
    "drs_rule_jsondata": {
      "changed": false,
      "drs_rule_info": {
        "cluster": [
          {
            "rule_affinity": true,
            "rule_enabled": true,
            "rule_key": 1,
            "rule_mandatory": null,
            "rule_name": "DEMO_REP_DRS_1",
            "rule_type": "vm_vm_rule",
            "rule_uuid": "522d41eb-4acb-afbf-9f37-15a1651ccf45",
            "rule_vms": [
              "VM1",
              "VM2",
              "VM3",
              "VM4"
            ]

        ]
      },
      "failed": false
    }
  },
  "_ansible_no_log": false,
  "changed": false
}

Expected results:

{
  "drs_rule": [
    {
      "rule_name": "DEMO_REP_DRS_1",
      "rule_affinity": true,
      "rule_vms": [
        "VM1",
        "VM2",
        "VM3",
        "VM4"
      ]
    }
  ]
}

Here is what ultimately worked in the end (which I though I had already tried):

              set_fact:
                drs_rule: "{{ drs_rule|default([]) + [ {
                  'rule_name': item | json_query('rule_name'),
                  'rule_affinity': item | json_query('rule_affinity'),
                  'rule_vms': item | json_query('rule_vms[*]')
                  } ] }}"
              vars:
                cluster_name: "{{ cluster_info.name }}"
              loop: "{{ drs_rule_jsondata.drs_rule_info[cluster_name] }}"

This expression doesn't make sense:

vars[path + '.' + cluster_name]

Here you're asking for a variable with the literal name drs_rule_jsondata.drs_rule_info.<value of cluster_name>, but there is no such variable -- that's not even a valid variable name.

You don't need to use vars here in any case; you can just refer to the top-level dns_rule_jsondata variable directly.

It's also not clear why you're using json_query in your playbook, since you're only asking for individual, static keys.

I think what you're trying to do is this:

- hosts: localhost
  gather_facts: false
  vars:
    cluster_info:
      name: cluster
    drs_rule_jsondata:
      changed: false
      drs_rule_info:
        cluster:
          - rule_affinity: true
            rule_enabled: true
            rule_key: 1
            rule_mandatory: null
            rule_name: DEMO_REP_DRS_1
            rule_type: vm_vm_rule
            rule_uuid: 522d41eb-4acb-afbf-9f37-15a1651ccf45
            rule_vms:
              - VM1
              - VM2
              - VM3
              - VM4

  tasks:
  - name: Set drs rule info
    set_fact:
      drs_rule: >-
        {{
           drs_rule + [
             {
            'rule_name': item.rule_name,
            'rule_affinity': item.rule_affinity,
            'rule_vms': item.rule_vms
            }
          ]
        }}
    vars:
      drs_rule: []
      cluster_name: "{{ cluster_info.name }}"
    loop: "{{ drs_rule_jsondata.drs_rule_info[cluster_name] }}"

  - debug:
      var: drs_rule

Running the above playbook produces as output:

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

TASK [Set drs rule info] *******************************************************
ok: [localhost] => (item={'rule_affinity': True, 'rule_enabled': True, 'rule_key': 1, 'rule_mandatory': None, 'rule_name': 'DEMO_REP_DRS_1', 'rule_type': 'vm_vm_rule', 'rule_uuid': '522d41eb-4acb-afbf-9f37-15a1651ccf45', 'rule_vms': ['VM1', 'VM2', 'VM3', 'VM4']})

TASK [debug] *******************************************************************
ok: [localhost] => {
    "drs_rule": [
        {
            "rule_affinity": true,
            "rule_name": "DEMO_REP_DRS_1",
            "rule_vms": [
                "VM1",
                "VM2",
                "VM3",
                "VM4"
            ]
        }
    ]
}

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