How can get an attribute after map()?

I have some JSON output I need to loop through. It's basically a list within a dictionary within a list, etc. Here's an example:

{
  "results": [
    {
      "children": {
        "attachment": {
          "results": [
            {
              "history": {},
              "title": "SomeTitle"
            }
          ]
        }
      }
    }
  ]
}

I need to iterate through the second results list (with the history and title, etc attributes) but I don't know how to get past the children attribute. Here's the filter I've tried:

results | map(attribute='children').attachment.results

It throws an error that the .attachment.results doesn't belong after map(). So what's the right way to accomplish this?

Solution

Use the lookup plugin subelements. How exactly you can use it depends on what attributes can change.

For example, given the list (to demonstrate the iteration let's add one more item to children.attachment.results)

  results1:
    - children:
        attachment:
          results:
            - history: {}
              title: SomeTitle
            - future: {}
              title: OtherTitle

the task

    - debug:
        msg: "{{ item }}"
      loop: "{{ results1|subelements('children.attachment.results') }}"
      loop_control:
        label: "{{ item.0.keys()|first }}"

gives

^{TASK [debug] **********************************************************************************
ok: [localhost] => (item=children) =>
msg:
- children:
attachment:
results:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle
- history: {}
title: SomeTitle
ok: [localhost] => (item=children) =>
msg:
- children:
attachment:
results:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle
- future: {}
title: OtherTitle}

The above iteration won't work if there are other dictionaries than children.*. For example,

  results2:
    - parents:
        attachment:
          results:
            - history: {}
              title: SomeTitle
            - future: {}
              title: OtherTitle
    - children:
        attachment:
          results:
            - history: {}
              title: SomeTitle
            - future: {}
              title: OtherTitle

In this case, convert the list to a dictionary

  results2_keys: "{{ results2|json_query('[][keys(@)]')|flatten(2) }}"
  results2_vals: "{{ results2|json_query('[].*.*.results')|flatten(2) }}"
  results2_dict: "{{ dict(results2_keys|zip(results2_vals)) }}"

gives

  results2_dict:
    children:
    - history: {}
      title: SomeTitle
    - future: {}
      title: OtherTitle
    parents:
    - history: {}
      title: SomeTitle
    - future: {}
      title: OtherTitle

Use this dictionary to iterate subelements

    - debug:
        msg: "{{ item }}"
      loop: "{{ results2_dict|dict2items|subelements('value') }}"
      loop_control:
        label: "{{ item.0.key }}"

gives

^{TASK [debug] **********************************************************************************
ok: [localhost] => (item=parents) =>
msg:
- key: parents
value:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle
- history: {}
title: SomeTitle
ok: [localhost] => (item=parents) =>
msg:
- key: parents
value:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle
- future: {}
title: OtherTitle
ok: [localhost] => (item=children) =>
msg:
- key: children
value:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle
- history: {}
title: SomeTitle
ok: [localhost] => (item=children) =>
msg:
- key: children
value:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle
- future: {}
title: OtherTitle}

To iterate other structures you can try and modify the json_query queries.

^{Example of a complete playbook for testing
- hosts: localhost

vars:

results1:
- children:
attachment:
results:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle

results2:
- parents:
attachment:
results:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle
- children:
attachment:
results:
- history: {}
title: SomeTitle
- future: {}
title: OtherTitle

results2_keys: "{{ results2|json_query('[][keys(@)]')|flatten(2) }}"
results2_vals: "{{ results2|json_query('[].*.*.results')|flatten(2) }}"
results2_dict: "{{ dict(results2_keys|zip(results2_vals)) }}"

tasks:

- debug:
msg: "{{ item }}"
loop: "{{ results1|subelements('children.attachment.results') }}"
loop_control:
label: "{{ item.0.keys()|first }}"

- debug:
var: results2_dict

- debug:
msg: "{{ item }}"
loop: "{{ results2_dict|dict2items|subelements('value') }}"
loop_control:
label: "{{ item.0.key }}"}