Function packageResolve

lib/internal/modules/esm/resolve.js:762–800

* Resolves a package specifier to a URL. * @param {string} specifier - The package specifier to resolve. * @param {string | URL | undefined} base - The base URL to use for resolution. * @param {Set } conditions - An object containing the conditions for resolution. * @returns {URL} - The r

(specifier, base, conditions)

 * @returns {URL} - The resolved URL.
 */
function packageResolve(specifier, base, conditions) {
  // TODO(@anonrig): Move this to a C++ function.
  if (BuiltinModule.canBeRequiredWithoutScheme(specifier)) {
    return new URL('node:' + specifier);
  }

  let packageJSONUrl, packageJSONPath, packageSubpath;

  if (hasPackageMap()) {
    // Package map is enabled - use it exclusively
    const parentPath = fileURLToPath(base);
    const mapped = packageMapResolve(specifier, parentPath);
    if (mapped === undefined) {
      throw new ERR_MODULE_NOT_FOUND(specifier, fileURLToPath(base), null);
    }
    const { packagePath, subpath } = mapped;
    packageJSONPath = join(packagePath, 'package.json');
    packageJSONUrl = pathToFileURL(packageJSONPath);
    packageSubpath = subpath;
  } else {
    // Standard node_modules resolution
    ({ packageJSONUrl, packageJSONPath, packageSubpath } =
      packageJsonReader.getPackageJSONURL(specifier, base));
  }

  const packageConfig = packageJsonReader.read(packageJSONPath, {
    __proto__: null, specifier, base, isESM: true,
  });

  if (packageConfig.exports != null) {
    return packageExportsResolve(
      packageJSONUrl, packageSubpath, packageConfig, base, conditions);
  }
  if (packageSubpath === '.') {
    return legacyMainResolve(packageJSONUrl, packageConfig, base);
  }

  return new URL(packageSubpath, packageJSONUrl);
}

/**
 * Checks if a specifier is a bare specifier.