serverless/lib/configuration/variables/sources/instance-dependent/get-sls.js

'use strict';

const ensureString = require('type/string/ensure');
const ServerlessError = require('../../../../serverless-error');

module.exports = (serverlessInstance) => {
  return {
    resolve: async ({ address, resolveConfigurationProperty, options }) => {
      if (!address) {
        throw new ServerlessError(
          'Missing address argument in variable "sls" source',
          'MISSING_SLS_SOURCE_ADDRESS'
        );
      }
      address = ensureString(address, {
        Error: ServerlessError,
        errorMessage: 'Non-string address argument in variable "sls" source: %v',
      });

      switch (address) {
        case 'instanceId':
          return { value: serverlessInstance.instanceId };
        case 'stage': {
          let stage = options.stage;
          if (!stage) stage = await resolveConfigurationProperty(['provider', 'stage']);
          if (!stage) stage = 'dev';
          return { value: stage };
        }
        default:
          throw new ServerlessError(
            `Unsupported "${address}" address argument in variable "sls" source`,
            'UNSUPPORTED_SLS_SOURCE_ADDRESS'
          );
      }
    },
  };
};