Function symlink

lib/fs.js:2159–2220

* Creates the link called `path` pointing to `target`. * @param {string | Buffer | URL} target * @param {string | Buffer | URL} path * @param {string | null} [type] * @param {(err?: Error) => any} callback * @returns {void}

(target, path, type, callback)

 * @returns {void}
 */
function symlink(target, path, type, callback) {
  if (callback === undefined) {
    callback = makeCallback(type);
    type = undefined;
  } else {
    validateOneOf(type, 'type', ['dir', 'file', 'junction', null, undefined]);
  }

  const h = vfsState.handlers;
  if (h !== null && vfsVoid(h.symlink(target, path, type), callback)) return;

  // Due to the nature of Node.js runtime, symlinks has different edge cases that can bypass
  // the permission model security guarantees. Thus, this API is disabled unless fs.read
  // and fs.write permission has been given.
  if (permission.isEnabled() && !permission.has('fs')) {
    callback(new ERR_ACCESS_DENIED('fs.symlink API requires full fs.read and fs.write permissions.'));
    return;
  }

  target = getValidatedPath(target, 'target');
  path = getValidatedPath(path);

  if (isWindows && type == null) {
    let absoluteTarget;
    try {
      // Symlinks targets can be relative to the newly created path.
      // Calculate absolute file name of the symlink target, and check
      // if it is a directory. Ignore resolve error to keep symlink
      // errors consistent between platforms if invalid path is
      // provided.
      absoluteTarget = pathModule.resolve(path, '..', target);
    } catch {
      // Continue regardless of error.
    }
    if (absoluteTarget !== undefined) {
      stat(absoluteTarget, (err, stat) => {
        const resolvedType = !err && stat.isDirectory() ? 'dir' : 'file';
        const resolvedFlags = stringToSymlinkType(resolvedType);
        const destination = preprocessSymlinkDestination(target,
                                                         resolvedType,
                                                         path);

        const req = new FSReqCallback();
        req.oncomplete = callback;
        binding.symlink(
          destination,
          path,
          resolvedFlags,
          req,
        );
      });
      return;
    }
  }

  const destination = preprocessSymlinkDestination(target, type, path);

  const flags = stringToSymlinkType(type);