Function shouldUseESMLoader

lib/internal/modules/run_main.js:52–84

* Determine whether the main entry point should be loaded through the ESM Loader. * @param {string} mainPath - Absolute path to the main entry point * @returns {boolean}

(mainPath)

 * @returns {boolean}
 */
function shouldUseESMLoader(mainPath) {
  /**
   * @type {string[]} userLoaders A list of custom loaders registered by the user
   * (or an empty list when none have been registered).
   */
  const userLoaders = getOptionValue('--experimental-loader');
  /**
   * @type {string[]} userImports A list of preloaded modules registered by the user
   * (or an empty list when none have been registered).
   */
  const userImports = getOptionValue('--import');
  if (userLoaders.length > 0 || userImports.length > 0) { return true; }

  // Determine the module format of the entry point.
  if (mainPath && StringPrototypeEndsWith(mainPath, '.mjs')) { return true; }
  if (mainPath && StringPrototypeEndsWith(mainPath, '.wasm')) { return true; }
  if (!mainPath || StringPrototypeEndsWith(mainPath, '.cjs')) { return false; }

  if (getOptionValue('--strip-types')) {
    if (!mainPath || StringPrototypeEndsWith(mainPath, '.cts')) { return false; }
    // This will likely change in the future to start with commonjs loader by default
    if (mainPath && StringPrototypeEndsWith(mainPath, '.mts')) { return true; }
  }

  const type = getNearestParentPackageJSONType(mainPath);

  // No package.json or no `type` field.
  if (type === undefined || type === 'none') {
    return false;
  }

  return type === 'module';
}

/**
 * @param {function(ModuleLoader):ModuleWrap|undefined} callback