Function legacyMainResolve

lib/internal/modules/esm/resolve.js:196–212

* Legacy CommonJS main resolution: * 1. let M = pkg_url + (json main field) * 2. TRY(M, M.js, M.json, M.node) * 3. TRY(M/index.js, M/index.json, M/index.node) * 4. TRY(pkg_url/index.js, pkg_url/index.json, pkg_url/index.node) * 5. NOT_FOUND * @param {URL} packageJSONUrl * @param {import('typi

(packageJSONUrl, packageConfig, base)

 * @returns {URL}
 */
function legacyMainResolve(packageJSONUrl, packageConfig, base) {
  assert(isURL(packageJSONUrl));
  const pkgPath = fileURLToPath(new URL('.', packageJSONUrl));

  const baseStringified = isURL(base) ? base.href : base;

  const resolvedOption = FSLegacyMainResolve(pkgPath, packageConfig.main, baseStringified);

  const maybeMain = resolvedOption <= legacyMainResolveExtensionsIndexes.kResolvedByMainIndexNode ?
    packageConfig.main || './' : '';
  const resolvedPath = resolve(pkgPath, maybeMain + legacyMainResolveExtensions[resolvedOption]);
  const resolvedUrl = pathToFileURL(resolvedPath);

  emitLegacyIndexDeprecation(resolvedUrl, resolvedPath, pkgPath, base, packageConfig.main);

  return resolvedUrl;
}

const encodedSepRegEx = /%2F|%5C/i;
/**