Ansible json_query() with variable as key

Question

I have following JSON input:

{
  "a goo": {
      "link": "google.com"
  }, 
  "b ms": {
      "link": "microsoft.com"
  }, 
  "c amz": {
    "link": "amazon.com"
  }
}

I'd like get the link string ("google.com"…) according to variable {{ target }} Content of {{ target }} variable will contains one of the "a goo", "b ms", "c amz" string.

Something like:

- name:
  set_fact:
    target: "c amz"
- debug:
    msg: "{{ input.json | json_query('{{ target }}'.link) }}"

Which should show:

   msg: "amazon.com"

Thank you for the advice.

+FE

Answer 1

Several problems in your expression:

1. In jmespath, identifiers are quoted with double quotes. Single quotes are used for strings. See jmespath specification.
2. The entire jmespath expression you pass to json_query should be a yaml/jinja2 string. As you wrote it, .link will be interpreted as a jinja2/yaml var identifier.
3. You must not imbricate the jinja2 template markers ({{ X }}). Moreover, in your current expression, '{{ target }}' is literally interpreted as a string not a variable to expand to its value.

The following playbook demonstrates one way to fix your current playbook and to acheive your requirement:

---
 - hosts: localhost
   gather_facts: false

   vars:
     input:
       json: { 
         "a goo": { 
           "link": "google.com"
         },
         "b ms": { 
           "link": "microsoft.com"
         },
         "c amz": { 
           "link": "amazon.com"
         } 
       } 

   tasks:
     - name: Debug the var we want to show
       vars:
         target: "c amz"
       debug:
         msg: "{{ input.json | json_query('\"' + target + '\".link') }}"

Which gives:

$ ansible-playbook play.yml 

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

TASK [Debug the var we want to show] *******************************************************************************************************************************************
ok: [localhost] => {
    "msg": "amazon.com"
}

PLAY RECAP *********************************************************************************************************************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0