@vercel/webpack-asset-relocator-loader/src/utils/get-package-base.js

Asset relocation loader used in ncc for performing Node.js builds while emitting and relocating any asset references.

// returns the base-level package folder based on detecting "node_modules"
// package name boundaries
const pkgNameRegEx = /^(@[^\\\/]+[\\\/])?[^\\\/]+/;
module.exports = function (id) {
  const pkgIndex = id.lastIndexOf('node_modules');
  if (pkgIndex !== -1 &&
      (id[pkgIndex - 1] === '/' || id[pkgIndex - 1] === '\\') &&
      (id[pkgIndex + 12] === '/' || id[pkgIndex + 12] === '\\')) {
    const pkgNameMatch = id.substr(pkgIndex + 13).match(pkgNameRegEx);
    if (pkgNameMatch)
      return id.substr(0, pkgIndex + 13 + pkgNameMatch[0].length);
  }
};

module.exports.pkgNameRegEx = pkgNameRegEx;