Function getEcmaVersion

src/utils.js:26–57

* Map a webpack `output.environment` configuration to the highest * ECMAScript version that the target is known to support. Returns `5` * when no ES2015+ features are flagged. * @param {NonNullable ["environment"]>} environment environment *

(environment)

 * @returns {number} ecma version (5, 2015, 2017 or 2020)
 */
function getEcmaVersion(environment) {
  // ES2020 (11th edition)
  if (
    environment.bigIntLiteral ||
    environment.dynamicImport ||
    environment.dynamicImportInWorker ||
    environment.globalThis ||
    environment.optionalChaining
  ) {
    return 2020;
  }

  // ES2017 (8th edition)
  if (environment.asyncFunction) {
    return 2017;
  }

  // ES2015 (6th edition)
  if (
    environment.arrowFunction ||
    environment.const ||
    environment.destructuring ||
    environment.forOf ||
    environment.methodShorthand ||
    environment.module ||
    environment.templateLiteral
  ) {
    return 2015;
  }

  return 5;
}

const notSettled = Symbol("not-settled");