How to loop over a JSON list in Ansible, filtered by values from a separate list?

Question

I have a list of user dictionaries that each contain username, gecos, etc, as well as a list of group dictionaries that each contain a list of group members. I need an Ansible task to loop over only the entries of the user list that match the member list of a specific group from the group list.

I suspect my problem has to do with proper use of quotations and Jinja delimiters so that everything gets evaluated at the proper level in the Ansible -> Jinja -> JMESPath hierarchy, but I haven't been able to determine exactly what I'm doing incorrectly. I've tried dozens of variants below, including breaking out the subqueries into their own variables, but without meaningful feedback I don't have much information to make improvements.

users.json:

{
  "aws_users": [
    {
      "name": "userA",
      "gecos": "User A"
    },
    {
      "name": "userB",
      "gecos": "User B"
    },
    {
      "name": "userC",
      "gecos": "User C"
    }
  ]
}

groups.json:

{
  "aws_groups": [
    {
      "name": "groupA",
      "members": [
        "userA",
        "userC"
      ]
    }
  ]
}

ansible.yml:

---
- hosts: 127.0.0.1
  become: true
  connection: local
  gather_facts: no
  vars_files:
    - ../../config/groups.json
    - ../../config/users.json

  vars:
     groupARoster: "{{ aws_groups | json_query('[?name==`groupA`].members | [0]') }}"
     query: "aws_users[?contains(`{{ groupARoster }}`, name)]"
     groupAUsers: "{{ aws_users | json_query(query) }}"

  tasks:
    - debug:
        var: groupARoster

    - debug:
        var: query

    - debug:
        var: groupAUsers

#    - name: Some looping thing
#      command: ...
#      loop: "{{ groupAusers }}"

Output:

PLAY [127.0.0.1] ***********************************************************************************************************************************************************************************************

TASK [debug] ***************************************************************************************************************************************************************************************************
ok: [127.0.0.1] => {
    "groupARoster": [
        "userA", 
        "userC"
    ]
}

TASK [debug] ***************************************************************************************************************************************************************************************************
ok: [127.0.0.1] => {
    "query": "aws_users[?contains(`[u'userA', u'userC']`, name)]"
}

TASK [debug] ***************************************************************************************************************************************************************************************************
ok: [127.0.0.1] => {
    "groupAUsers": ""
}

PLAY RECAP *****************************************************************************************************************************************************************************************************
127.0.0.1                  : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0 

Desired Output (for passing into an Ansible loop parameter):

"groupAUsers": [
    {
      "name": "userA",
      "gecos": "User A"
    },
    {
      "name": "userC",
      "gecos": "User C"
    }
  ]

Answer 1

Unless you really want to use jmespath for this, there is an easier way IMO using selectattr:

groupARoster: "{{ (aws_groups | selectattr('name', 'equalto', 'groupA') | list)[0].members }}"
groupAUsers: "{{ aws_users | selectattr('name', 'in', groupARoster) | list }}"

Meanwhile this is still possible with json_query. You were really close. The problem is your intermediate query. You are passing the variable aws_user to json_query. Hence there is no first level "aws_user" key in the value you pass. You have to drop it from the query:

groupARoster: "{{ aws_groups | json_query('[?name==`groupA`].members | [0]') }}"
query: "[?contains(`{{ groupARoster }}`, name)]"
groupAUsers: "{{ aws_users | json_query(query) }}"