Serverless Plugin that stringify's a JSON input

serverless-plugin-json.js

'use strict';

class ServerlessPluginJSON {
  constructor() {
    this.configurationVariablesSources = {
      jsonStringify: {
        async resolve({ params }) {
          return {
            value: JSON.stringify( (params[0] || {}) ),
          };
        },
      },
      jsonParse: {
        async resolve({ params }) {
          return {
            value: JSON.parse( (params[0] || "") ),
          };
        },
      },
    };
  }
}

module.exports = ServerlessPluginJSON;

serverless.yml

plugins:
  - ./serverless-plugin-json.js

service: demo

custom:
  # config key to store in Parameter Store
  myConfigKey:
    - name: 'app_instance_1'
      group_map:
        - azure_group: 'instance1_viewer'
          app_role: 'viewer'
        - azure_group: 'app_admin'
          app_role: 'admin'
    - name: 'app_instance_2'
      group_map:
        - azure_group: 'instance2_viewer'
          app_role: 'viewer'
        - azure_group: 'app_admin'
          app_role: 'admin'

  example_1: ${jsonStringify(${self:custom.myConfigKey})}
  # => "[{\"name\":\"app_instance_1\",\"group_map\":[{\"azure_group\":\"instance1_viewer\",\"app_role\":\"viewer\"},{\"azure_group\":\"app_admin\",\"app_role\":\"admin\"}]},{\"name\":\"app_instance_2\",\"group_map\":[{\"azure_group\":\"instance2_viewer\",\"app_role\":\"viewer\"},{\"azure_group\":\"app_admin\",\"app_role\":\"admin\"}]}]",

  example_2: ${jsonStringify()}
  # => {}

  example_3: ${jsonParse(${self:custom.example_1})}
  # =>  [
  #       {
  #         "name": "app_instance_1",
  #         "group_map": [
  #           {
  #             "azure_group": "instance1_viewer",
  #             "app_role": "viewer"
  #           },
  #           {
  #             "azure_group": "app_admin",
  #             "app_role": "admin"
  #           }
  #         ]
  #       },
  #       {
  #         "name": "app_instance_2",
  #         "group_map": [
  #           {
  #             "azure_group": "instance2_viewer",
  #             "app_role": "viewer"
  #           },
  #           {
  #             "azure_group": "app_admin",
  #             "app_role": "admin"
  #           }
  #         ]
  #       }
  #     ]

provider:
  name: aws
  stage: ${opt:stage, 'test'}

resources:
  Resources:

    SSMParameter:
      Type: AWS::SSM::Parameter
      Properties:
        Name: '/${self:provider.stage}/${self:service}/some_json_parameter_that_is_stored_as_string'
        Type: String
        Value: ${jsonStringify( ${self:custom.myConfigKey} )}