Need to replace value in dictionary in destination file with the value in the dictionary in source file

Question

I have been trying to update the values in a dictionary in destination json with the values in the dictionary in source JSON file. Below is the example of source and destination JSON file:

Source file:

[
        {
                "key": "MYSQL",
                "value": "456"
        },
        {
                "key": "RDS",
                "value": "123"
        }
]

Destination File:

[
        {
                "key": "MYSQL",
                "value": "100"
        },
        {
                "key": "RDS",
                "value": "111"
        },
        {
                "key": "DB1",
                "value": "TestDB"
        },
        {
                "key": "OS",
                "value": "EX1"
        }
]

Expectation in destination file after running Ansible playbook:

[
        {
                "key": "MYSQL",
                "value": "**456**"
        },
        {
                "key": "RDS",
                "value": "**123**"
        },
        {
                "key": "DB1",
                "value": "TestDB"
        },
        {
                "key": "OS",
                "value": "EX1"
        }
]

Below is the playbook I have tried so far, but this only updates the value if it is hard coded:

- hosts: localhost
  tasks:

  - name: Parse JSON
    shell: cat Source.json
    register: result

  - name: Save json data to a variable
    set_fact:
      jsondata: "{{result.stdout | from_json}}"

  - name: Get key names
    set_fact:
      json_key: "{{ jsondata | map(attribute='key') | flatten }}"

  - name: Get Values names
    set_fact:
      json_value: "{{ jsondata | map(attribute='value') | flatten }}"

  # Trying to update the destination file with only the values provided in source.json
  - name: Replace values in json
    replace:
      path: Destination.json
      regexp: '"{{ item }}": "100"'
      replace: '"{{ item }}": "456"'
    loop:
    - value

The main goal is to update the value in destination.json with the value provided in source.json.

Answer 1

In Ansible, the couple key/value tends to be handled with the filters dict2items and items2dict. And your use case can be handled by those filters.

Here would be the logic:

• Read both files
• Convert both files into dictionaries, with dict2items
• Combine the two dictionaries, with the combine filter
• Convert the dictionary back into a list with items2dict
• Dump the result in JSON back into the file

---

Given the playbook:

- hosts: localhost
  gather_facts: no

  tasks:
    - shell: cat Source.json
      register: source

    - shell: cat Destination.json
      register: destination

    - copy:
        content: "{{ 
            destination.stdout | from_json | items2dict | 
            combine(
              source.stdout | from_json | items2dict
            ) | dict2items | to_nice_json
          }}"
        dest: Destination.json

We end up with Destination.json containing:

[
    {
        "key": "MYSQL",
        "value": "456"
    },
    {
        "key": "RDS",
        "value": "123"
    },
    {
        "key": "DB1",
        "value": "TestDB"
    },
    {
        "key": "OS",
        "value": "EX1"
    }
]

Answer 2

Without to knowing the structure of your destination file it's difficult to use a regex.
I suggest you to load your destination file in a variable, do the changes and save the content of variable to file.

This solution does the job:

- hosts: localhost
  tasks:

    - name: Parse JSON
      set_fact:
        source: "{{ lookup('file', 'source.json') | from_json }}"
        destination: "{{ lookup('file', 'destination.json') | from_json }}"

    - name: create new json
      set_fact:
        json_new: "{{ json_new | d([]) + ([item] if _rec == [] else [_rec]) | flatten }}"
      loop: "{{ destination }}"
      vars:
        _rec: "{{ source | selectattr('key', 'equalto', item.key) }}"


    - name: save new json
      copy:
        content: "{{ json_new | to_nice_json }}"
        dest: dest_new.json

Result -> dest_new.json:

ok: [localhost] => {
    "msg": [
        {
            "key": "MYSQL",
            "value": "456"
        },
        {
            "key": "RDS",
            "value": "123"
        },
        {
            "key": "DB1",
            "value": "TestDB"
        },
        {
            "key": "OS",
            "value": "EX1"
        }
    ]
}