Function moduleResolve

lib/internal/modules/esm/resolve.js:845–880

* Resolves a module specifier to a URL. * @param {string} specifier - The module specifier to resolve. * @param {string | URL | undefined} base - The base URL to resolve against. * @param {Set } conditions - An object containing environment conditions. * @param {boolean} preserveSymlinks

(specifier, base, conditions, preserveSymlinks)

 * @returns {URL}
 */
function moduleResolve(specifier, base, conditions, preserveSymlinks) {
  const protocol = typeof base === 'string' ?
    StringPrototypeSlice(base, 0, StringPrototypeIndexOf(base, ':') + 1) :
    base.protocol;
  const isData = protocol === 'data:';
  // Order swapped from spec for minor perf gain.
  // Ok since relative URLs cannot parse as URLs.
  let resolved;
  if (shouldBeTreatedAsRelativeOrAbsolutePath(specifier)) {
    try {
      resolved = new URL(specifier, base);
    } catch (cause) {
      const error = new ERR_UNSUPPORTED_RESOLVE_REQUEST(specifier, base);
      setOwnProperty(error, 'cause', cause);
      throw error;
    }
  } else if (protocol === 'file:' && specifier[0] === '#') {
    resolved = packageImportsResolve(specifier, base, conditions);
  } else {
    const url = URLParse(specifier);
    if (url !== null) {
      resolved = url;
    } else {
      if (isData && !BuiltinModule.canBeRequiredWithoutScheme(specifier)) {
        const error = new ERR_UNSUPPORTED_RESOLVE_REQUEST(specifier, base);
        setOwnProperty(error, 'cause', new ERR_INVALID_URL(specifier));
        throw error;
      }
      resolved = packageResolve(specifier, base, conditions);
    }
  }
  if (resolved.protocol !== 'file:') {
    return resolved;
  }
  return finalizeResolution(resolved, base, preserveSymlinks);
}

/**
 * Try to resolve an import as a CommonJS module.