Write output of ansible task to file in proper JSON format

Question

I'm trying to write shell task output to json, but I have the problem of parsing it in a valid one json file.

This is example of shell task output: {"firstname": "John", "lastname": "Smith", "user": "john"}

- name: 'Execute script'
  shell: /tmp/script.sh
  register: script_output

- name: 'Output to json'
  local_action:
    module: lineinfile
    dest: output.json
    line: '{{ script_output.stdout }}'
    create: yes

After playbook execution, the json file has the following content:

{"firstname": "John", "lastname": "Smith", "user": "john"}
{"firstname": "John", "lastname": "Smith", "user": "john"}
{"firstname": "John", "lastname": "Smith", "user": "john"}

How can I format the output in the json valid format as attached?

[
    {"firstname": "John", "lastname": "Smith", "user": "john"},
    {"firstname": "John", "lastname": "Smith", "user": "john"},
    {"firstname": "John", "lastname": "Smith", "user": "john"}
]

Solution

There is no ansible json module for doing this. But you can use third-party modules like ansible-jsonpatch for this.