I am attempting to use ansible to toggle the encryption state of a specified file (encrypt the file if decrypted, decrypt it if encrypted) using the ansible filter “ternary”.

This is my playbook:

---
# site.yml

- name: site playbook (dummy site)
  hosts: localhost
  gather_facts: no

  vars:
    file:   test_key_file
    cmd_encrypt: ansible-vault encrypt {{ file }}
    cmd_decrypt: ansible-vault decrypt {{ file }}

  tasks:
    - local_action: shell
      head -1 {{ file }} | grep -v -q $ANSIBLE_VAULT | ternary( "{{ cmd_encrypt }}" , "{{ cmd_decrypt }}"  )

The first part of the shell command was taken from here. I added the ternary part. I have tried various modifications regarding quotes and curly-braces, and substituting values for variables to no avail.

The configuration above results in the error:

ERROR! We were unable to read either as JSON nor YAML, these are the errors we got from each:
JSON: Expecting value: line 1 column 1 (char 0)

Syntax Error while loading YAML.
  could not find expected ':'

The error appears to be in '/home/sjf/toggle_encryption_test/site.yml': line 16, column 1, but may
be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:

    - local_action: shell
      head -1 {{ file }} | grep -v -q $ANSIBLE_VAULT | ternary( "{{ cmd_encrypt }}" , "{{ cmd_decrypt }}"  )
^ here
We could be wrong, but this one looks like it might be an issue with
missing quotes. Always quote template expression brackets when they
start a value. For instance:

    with_items:
      - {{ foo }}

Should be written as:

    with_items:
      - "{{ foo }}"

Any help would be appreciated.