Function tryPackage

lib/internal/modules/cjs/loader.js:548–582

* Try to load a specifier as a package. * @param {string} requestPath The path to what we are trying to load * @param {string[]} exts File extensions to try appending in order to resolve the file * @param {boolean} isMain Whether the file is the main entry point of the app * @param {string} orig

(requestPath, exts, isMain, originalPath)

 * @returns {any}
 */
function tryPackage(requestPath, exts, isMain, originalPath) {
  const { main: pkg, pjsonPath } = _readPackage(requestPath);

  if (!pkg) {
    return tryExtensions(path.resolve(requestPath, 'index'), exts, isMain);
  }

  const filename = path.resolve(requestPath, pkg);
  let actual = tryFile(filename, isMain) ||
    tryExtensions(filename, exts, isMain) ||
    tryExtensions(path.resolve(filename, 'index'), exts, isMain);
  if (actual === false) {
    actual = tryExtensions(path.resolve(requestPath, 'index'), exts, isMain);
    if (!actual) {
      // eslint-disable-next-line no-restricted-syntax
      const err = new Error(
        `Cannot find module '${filename}'. ` +
        'Please verify that the package.json has a valid "main" entry',
      );
      err.code = 'MODULE_NOT_FOUND';
      err.path = pjsonPath;
      err.requestPath = originalPath;
      // TODO(BridgeAR): Add the requireStack as well.
      throw err;
    } else {
      process.emitWarning(
        `Invalid 'main' field in '${pjsonPath}' of '${pkg}'. ` +
          'Please either fix that or report it to the module author',
        'DeprecationWarning',
        'DEP0128',
      );
    }
  }
  return actual;
}

/**
 * Check if the file exists and is not a directory if using `--preserve-symlinks` and `isMain` is false or