Function mergeConfig

lib/core/mergeConfig.js:17–159

(config1, config2)

 * @returns {Object} New object resulting from merging config2 to config1
 */
export default function mergeConfig(config1, config2) {
  // eslint-disable-next-line no-param-reassign
  config1 = config1 || {};
  config2 = config2 || {};

  // Use a null-prototype object so that downstream reads such as `config.auth`
  // or `config.baseURL` cannot inherit polluted values from Object.prototype.
  // `hasOwnProperty` is restored as a non-enumerable own slot to preserve
  // ergonomics for user code that relies on it.
  const config = Object.create(null);
  Object.defineProperty(config, 'hasOwnProperty', {
    // Null-proto descriptor so a polluted Object.prototype.get cannot turn
    // this data descriptor into an accessor descriptor on the way in.
    __proto__: null,
    value: Object.prototype.hasOwnProperty,
    enumerable: false,
    writable: true,
    configurable: true,
  });

  function getMergedValue(target, source, prop, caseless) {
    if (utils.isPlainObject(target) && utils.isPlainObject(source)) {
      return utils.merge.call({ caseless }, target, source);
    } else if (utils.isPlainObject(source)) {
      return utils.merge({}, source);
    } else if (utils.isArray(source)) {
      return source.slice();
    }
    return source;
  }

  function mergeDeepProperties(a, b, prop, caseless) {
    if (!utils.isUndefined(b)) {
      return getMergedValue(a, b, prop, caseless);
    } else if (!utils.isUndefined(a)) {
      return getMergedValue(undefined, a, prop, caseless);
    }
  }

  // eslint-disable-next-line consistent-return
  function valueFromConfig2(a, b) {
    if (!utils.isUndefined(b)) {
      return getMergedValue(undefined, b);
    }
  }

  // eslint-disable-next-line consistent-return
  function defaultToConfig2(a, b) {
    if (!utils.isUndefined(b)) {
      return getMergedValue(undefined, b);
    } else if (!utils.isUndefined(a)) {
      return getMergedValue(undefined, a);
    }
  }

  function getMergedTransitionalOption(prop) {
    const transitional2 = utils.hasOwnProp(config2, 'transitional') ? config2.transitional : undefined;