implemented basic client-server communication

node_modules/chokidar/lib/constants.js

@@ -0,0 +1,65 @@
+'use strict';
+
+const {sep} = require('path');
+const {platform} = process;
+const os = require('os');
+
+exports.EV_ALL = 'all';
+exports.EV_READY = 'ready';
+exports.EV_ADD = 'add';
+exports.EV_CHANGE = 'change';
+exports.EV_ADD_DIR = 'addDir';
+exports.EV_UNLINK = 'unlink';
+exports.EV_UNLINK_DIR = 'unlinkDir';
+exports.EV_RAW = 'raw';
+exports.EV_ERROR = 'error';
+
+exports.STR_DATA = 'data';
+exports.STR_END = 'end';
+exports.STR_CLOSE = 'close';
+
+exports.FSEVENT_CREATED = 'created';
+exports.FSEVENT_MODIFIED = 'modified';
+exports.FSEVENT_DELETED = 'deleted';
+exports.FSEVENT_MOVED = 'moved';
+exports.FSEVENT_CLONED = 'cloned';
+exports.FSEVENT_UNKNOWN = 'unknown';
+exports.FSEVENT_TYPE_FILE = 'file';
+exports.FSEVENT_TYPE_DIRECTORY = 'directory';
+exports.FSEVENT_TYPE_SYMLINK = 'symlink';
+
+exports.KEY_LISTENERS = 'listeners';
+exports.KEY_ERR = 'errHandlers';
+exports.KEY_RAW = 'rawEmitters';
+exports.HANDLER_KEYS = [exports.KEY_LISTENERS, exports.KEY_ERR, exports.KEY_RAW];
+
+exports.DOT_SLASH = `.${sep}`;
+
+exports.BACK_SLASH_RE = /\\/g;
+exports.DOUBLE_SLASH_RE = /\/\//;
+exports.SLASH_OR_BACK_SLASH_RE = /[/\\]/;
+exports.DOT_RE = /\..*\.(sw[px])$|~$|\.subl.*\.tmp/;
+exports.REPLACER_RE = /^\.[/\\]/;
+
+exports.SLASH = '/';
+exports.SLASH_SLASH = '//';
+exports.BRACE_START = '{';
+exports.BANG = '!';
+exports.ONE_DOT = '.';
+exports.TWO_DOTS = '..';
+exports.STAR = '*';
+exports.GLOBSTAR = '**';
+exports.ROOT_GLOBSTAR = '/**/*';
+exports.SLASH_GLOBSTAR = '/**';
+exports.DIR_SUFFIX = 'Dir';
+exports.ANYMATCH_OPTS = {dot: true};
+exports.STRING_TYPE = 'string';
+exports.FUNCTION_TYPE = 'function';
+exports.EMPTY_STR = '';
+exports.EMPTY_FN = () => {};
+exports.IDENTITY_FN = val => val;
+
+exports.isWindows = platform === 'win32';
+exports.isMacos = platform === 'darwin';
+exports.isLinux = platform === 'linux';
+exports.isIBMi = os.type() === 'OS400';

node_modules/chokidar/lib/fsevents-handler.js

@@ -0,0 +1,524 @@
+'use strict';
+
+const fs = require('fs');
+const sysPath = require('path');
+const { promisify } = require('util');
+
+let fsevents;
+try {
+  fsevents = require('fsevents');
+} catch (error) {
+  if (process.env.CHOKIDAR_PRINT_FSEVENTS_REQUIRE_ERROR) console.error(error);
+}
+
+if (fsevents) {
+  // TODO: real check
+  const mtch = process.version.match(/v(\d+)\.(\d+)/);
+  if (mtch && mtch[1] && mtch[2]) {
+    const maj = Number.parseInt(mtch[1], 10);
+    const min = Number.parseInt(mtch[2], 10);
+    if (maj === 8 && min < 16) {
+      fsevents = undefined;
+    }
+  }
+}
+
+const {
+  EV_ADD,
+  EV_CHANGE,
+  EV_ADD_DIR,
+  EV_UNLINK,
+  EV_ERROR,
+  STR_DATA,
+  STR_END,
+  FSEVENT_CREATED,
+  FSEVENT_MODIFIED,
+  FSEVENT_DELETED,
+  FSEVENT_MOVED,
+  // FSEVENT_CLONED,
+  FSEVENT_UNKNOWN,
+  FSEVENT_TYPE_FILE,
+  FSEVENT_TYPE_DIRECTORY,
+  FSEVENT_TYPE_SYMLINK,
+
+  ROOT_GLOBSTAR,
+  DIR_SUFFIX,
+  DOT_SLASH,
+  FUNCTION_TYPE,
+  EMPTY_FN,
+  IDENTITY_FN
+} = require('./constants');
+
+const Depth = (value) => isNaN(value) ? {} : {depth: value};
+
+const stat = promisify(fs.stat);
+const lstat = promisify(fs.lstat);
+const realpath = promisify(fs.realpath);
+
+const statMethods = { stat, lstat };
+
+/**
+ * @typedef {String} Path
+ */
+
+/**
+ * @typedef {Object} FsEventsWatchContainer
+ * @property {Set<Function>} listeners
+ * @property {Function} rawEmitter
+ * @property {{stop: Function}} watcher
+ */
+
+// fsevents instance helper functions
+/**
+ * Object to hold per-process fsevents instances (may be shared across chokidar FSWatcher instances)
+ * @type {Map<Path,FsEventsWatchContainer>}
+ */
+const FSEventsWatchers = new Map();
+
+// Threshold of duplicate path prefixes at which to start
+// consolidating going forward
+const consolidateThreshhold = 10;
+
+const wrongEventFlags = new Set([
+  69888, 70400, 71424, 72704, 73472, 131328, 131840, 262912
+]);
+
+/**
+ * Instantiates the fsevents interface
+ * @param {Path} path path to be watched
+ * @param {Function} callback called when fsevents is bound and ready
+ * @returns {{stop: Function}} new fsevents instance
+ */
+const createFSEventsInstance = (path, callback) => {
+  const stop = fsevents.watch(path, callback);
+  return {stop};
+};
+
+/**
+ * Instantiates the fsevents interface or binds listeners to an existing one covering
+ * the same file tree.
+ * @param {Path} path           - to be watched
+ * @param {Path} realPath       - real path for symlinks
+ * @param {Function} listener   - called when fsevents emits events
+ * @param {Function} rawEmitter - passes data to listeners of the 'raw' event
+ * @returns {Function} closer
+ */
+function setFSEventsListener(path, realPath, listener, rawEmitter) {
+  let watchPath = sysPath.extname(realPath) ? sysPath.dirname(realPath) : realPath;
+
+  const parentPath = sysPath.dirname(watchPath);
+  let cont = FSEventsWatchers.get(watchPath);
+
+  // If we've accumulated a substantial number of paths that
+  // could have been consolidated by watching one directory
+  // above the current one, create a watcher on the parent
+  // path instead, so that we do consolidate going forward.
+  if (couldConsolidate(parentPath)) {
+    watchPath = parentPath;
+  }
+
+  const resolvedPath = sysPath.resolve(path);
+  const hasSymlink = resolvedPath !== realPath;
+
+  const filteredListener = (fullPath, flags, info) => {
+    if (hasSymlink) fullPath = fullPath.replace(realPath, resolvedPath);
+    if (
+      fullPath === resolvedPath ||
+      !fullPath.indexOf(resolvedPath + sysPath.sep)
+    ) listener(fullPath, flags, info);
+  };
+
+  // check if there is already a watcher on a parent path
+  // modifies `watchPath` to the parent path when it finds a match
+  let watchedParent = false;
+  for (const watchedPath of FSEventsWatchers.keys()) {
+    if (realPath.indexOf(sysPath.resolve(watchedPath) + sysPath.sep) === 0) {
+      watchPath = watchedPath;
+      cont = FSEventsWatchers.get(watchPath);
+      watchedParent = true;
+      break;
+    }
+  }
+
+  if (cont || watchedParent) {
+    cont.listeners.add(filteredListener);
+  } else {
+    cont = {
+      listeners: new Set([filteredListener]),
+      rawEmitter,
+      watcher: createFSEventsInstance(watchPath, (fullPath, flags) => {
+        if (!cont.listeners.size) return;
+        const info = fsevents.getInfo(fullPath, flags);
+        cont.listeners.forEach(list => {
+          list(fullPath, flags, info);
+        });
+
+        cont.rawEmitter(info.event, fullPath, info);
+      })
+    };
+    FSEventsWatchers.set(watchPath, cont);
+  }
+
+  // removes this instance's listeners and closes the underlying fsevents
+  // instance if there are no more listeners left
+  return () => {
+    const lst = cont.listeners;
+
+    lst.delete(filteredListener);
+    if (!lst.size) {
+      FSEventsWatchers.delete(watchPath);
+      if (cont.watcher) return cont.watcher.stop().then(() => {
+        cont.rawEmitter = cont.watcher = undefined;
+        Object.freeze(cont);
+      });
+    }
+  };
+}
+
+// Decide whether or not we should start a new higher-level
+// parent watcher
+const couldConsolidate = (path) => {
+  let count = 0;
+  for (const watchPath of FSEventsWatchers.keys()) {
+    if (watchPath.indexOf(path) === 0) {
+      count++;
+      if (count >= consolidateThreshhold) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+};
+
+// returns boolean indicating whether fsevents can be used
+const canUse = () => fsevents && FSEventsWatchers.size < 128;
+
+// determines subdirectory traversal levels from root to path
+const calcDepth = (path, root) => {
+  let i = 0;
+  while (!path.indexOf(root) && (path = sysPath.dirname(path)) !== root) i++;
+  return i;
+};
+
+// returns boolean indicating whether the fsevents' event info has the same type
+// as the one returned by fs.stat
+const sameTypes = (info, stats) => (
+  info.type === FSEVENT_TYPE_DIRECTORY && stats.isDirectory() ||
+  info.type === FSEVENT_TYPE_SYMLINK && stats.isSymbolicLink() ||
+  info.type === FSEVENT_TYPE_FILE && stats.isFile()
+)
+
+/**
+ * @mixin
+ */
+class FsEventsHandler {
+
+/**
+ * @param {import('../index').FSWatcher} fsw
+ */
+constructor(fsw) {
+  this.fsw = fsw;
+}
+checkIgnored(path, stats) {
+  const ipaths = this.fsw._ignoredPaths;
+  if (this.fsw._isIgnored(path, stats)) {
+    ipaths.add(path);
+    if (stats && stats.isDirectory()) {
+      ipaths.add(path + ROOT_GLOBSTAR);
+    }
+    return true;
+  }
+
+  ipaths.delete(path);
+  ipaths.delete(path + ROOT_GLOBSTAR);
+}
+
+addOrChange(path, fullPath, realPath, parent, watchedDir, item, info, opts) {
+  const event = watchedDir.has(item) ? EV_CHANGE : EV_ADD;
+  this.handleEvent(event, path, fullPath, realPath, parent, watchedDir, item, info, opts);
+}
+
+async checkExists(path, fullPath, realPath, parent, watchedDir, item, info, opts) {
+  try {
+    const stats = await stat(path)
+    if (this.fsw.closed) return;
+    if (sameTypes(info, stats)) {
+      this.addOrChange(path, fullPath, realPath, parent, watchedDir, item, info, opts);
+    } else {
+      this.handleEvent(EV_UNLINK, path, fullPath, realPath, parent, watchedDir, item, info, opts);
+    }
+  } catch (error) {
+    if (error.code === 'EACCES') {
+      this.addOrChange(path, fullPath, realPath, parent, watchedDir, item, info, opts);
+    } else {
+      this.handleEvent(EV_UNLINK, path, fullPath, realPath, parent, watchedDir, item, info, opts);
+    }
+  }
+}
+
+handleEvent(event, path, fullPath, realPath, parent, watchedDir, item, info, opts) {
+  if (this.fsw.closed || this.checkIgnored(path)) return;
+
+  if (event === EV_UNLINK) {
+    const isDirectory = info.type === FSEVENT_TYPE_DIRECTORY
+    // suppress unlink events on never before seen files
+    if (isDirectory || watchedDir.has(item)) {
+      this.fsw._remove(parent, item, isDirectory);
+    }
+  } else {
+    if (event === EV_ADD) {
+      // track new directories
+      if (info.type === FSEVENT_TYPE_DIRECTORY) this.fsw._getWatchedDir(path);
+
+      if (info.type === FSEVENT_TYPE_SYMLINK && opts.followSymlinks) {
+        // push symlinks back to the top of the stack to get handled
+        const curDepth = opts.depth === undefined ?
+          undefined : calcDepth(fullPath, realPath) + 1;
+        return this._addToFsEvents(path, false, true, curDepth);
+      }
+
+      // track new paths
+      // (other than symlinks being followed, which will be tracked soon)
+      this.fsw._getWatchedDir(parent).add(item);
+    }
+    /**
+     * @type {'add'|'addDir'|'unlink'|'unlinkDir'}
+     */
+    const eventName = info.type === FSEVENT_TYPE_DIRECTORY ? event + DIR_SUFFIX : event;
+    this.fsw._emit(eventName, path);
+    if (eventName === EV_ADD_DIR) this._addToFsEvents(path, false, true);
+  }
+}
+
+/**
+ * Handle symlinks encountered during directory scan
+ * @param {String} watchPath  - file/dir path to be watched with fsevents
+ * @param {String} realPath   - real path (in case of symlinks)
+ * @param {Function} transform  - path transformer
+ * @param {Function} globFilter - path filter in case a glob pattern was provided
+ * @returns {Function} closer for the watcher instance
+*/
+_watchWithFsEvents(watchPath, realPath, transform, globFilter) {
+  if (this.fsw.closed || this.fsw._isIgnored(watchPath)) return;
+  const opts = this.fsw.options;
+  const watchCallback = async (fullPath, flags, info) => {
+    if (this.fsw.closed) return;
+    if (
+      opts.depth !== undefined &&
+      calcDepth(fullPath, realPath) > opts.depth
+    ) return;
+    const path = transform(sysPath.join(
+      watchPath, sysPath.relative(watchPath, fullPath)
+    ));
+    if (globFilter && !globFilter(path)) return;
+    // ensure directories are tracked
+    const parent = sysPath.dirname(path);
+    const item = sysPath.basename(path);
+    const watchedDir = this.fsw._getWatchedDir(
+      info.type === FSEVENT_TYPE_DIRECTORY ? path : parent
+    );
+
+    // correct for wrong events emitted
+    if (wrongEventFlags.has(flags) || info.event === FSEVENT_UNKNOWN) {
+      if (typeof opts.ignored === FUNCTION_TYPE) {
+        let stats;
+        try {
+          stats = await stat(path);
+        } catch (error) {}
+        if (this.fsw.closed) return;
+        if (this.checkIgnored(path, stats)) return;
+        if (sameTypes(info, stats)) {
+          this.addOrChange(path, fullPath, realPath, parent, watchedDir, item, info, opts);
+        } else {
+          this.handleEvent(EV_UNLINK, path, fullPath, realPath, parent, watchedDir, item, info, opts);
+        }
+      } else {
+        this.checkExists(path, fullPath, realPath, parent, watchedDir, item, info, opts);
+      }
+    } else {
+      switch (info.event) {
+      case FSEVENT_CREATED:
+      case FSEVENT_MODIFIED:
+        return this.addOrChange(path, fullPath, realPath, parent, watchedDir, item, info, opts);
+      case FSEVENT_DELETED:
+      case FSEVENT_MOVED:
+        return this.checkExists(path, fullPath, realPath, parent, watchedDir, item, info, opts);
+      }
+    }
+  };
+
+  const closer = setFSEventsListener(
+    watchPath,
+    realPath,
+    watchCallback,
+    this.fsw._emitRaw
+  );
+
+  this.fsw._emitReady();
+  return closer;
+}
+
+/**
+ * Handle symlinks encountered during directory scan
+ * @param {String} linkPath path to symlink
+ * @param {String} fullPath absolute path to the symlink
+ * @param {Function} transform pre-existing path transformer
+ * @param {Number} curDepth level of subdirectories traversed to where symlink is
+ * @returns {Promise<void>}
+ */
+async _handleFsEventsSymlink(linkPath, fullPath, transform, curDepth) {
+  // don't follow the same symlink more than once
+  if (this.fsw.closed || this.fsw._symlinkPaths.has(fullPath)) return;
+
+  this.fsw._symlinkPaths.set(fullPath, true);
+  this.fsw._incrReadyCount();
+
+  try {
+    const linkTarget = await realpath(linkPath);
+    if (this.fsw.closed) return;
+    if (this.fsw._isIgnored(linkTarget)) {
+      return this.fsw._emitReady();
+    }
+
+    this.fsw._incrReadyCount();
+
+    // add the linkTarget for watching with a wrapper for transform
+    // that causes emitted paths to incorporate the link's path
+    this._addToFsEvents(linkTarget || linkPath, (path) => {
+      let aliasedPath = linkPath;
+      if (linkTarget && linkTarget !== DOT_SLASH) {
+        aliasedPath = path.replace(linkTarget, linkPath);
+      } else if (path !== DOT_SLASH) {
+        aliasedPath = sysPath.join(linkPath, path);
+      }
+      return transform(aliasedPath);
+    }, false, curDepth);
+  } catch(error) {
+    if (this.fsw._handleError(error)) {
+      return this.fsw._emitReady();
+    }
+  }
+}
+
+/**
+ *
+ * @param {Path} newPath
+ * @param {fs.Stats} stats
+ */
+emitAdd(newPath, stats, processPath, opts, forceAdd) {
+  const pp = processPath(newPath);
+  const isDir = stats.isDirectory();
+  const dirObj = this.fsw._getWatchedDir(sysPath.dirname(pp));
+  const base = sysPath.basename(pp);
+
+  // ensure empty dirs get tracked
+  if (isDir) this.fsw._getWatchedDir(pp);
+  if (dirObj.has(base)) return;
+  dirObj.add(base);
+
+  if (!opts.ignoreInitial || forceAdd === true) {
+    this.fsw._emit(isDir ? EV_ADD_DIR : EV_ADD, pp, stats);
+  }
+}
+
+initWatch(realPath, path, wh, processPath) {
+  if (this.fsw.closed) return;
+  const closer = this._watchWithFsEvents(
+    wh.watchPath,
+    sysPath.resolve(realPath || wh.watchPath),
+    processPath,
+    wh.globFilter
+  );
+  this.fsw._addPathCloser(path, closer);
+}
+
+/**
+ * Handle added path with fsevents
+ * @param {String} path file/dir path or glob pattern
+ * @param {Function|Boolean=} transform converts working path to what the user expects
+ * @param {Boolean=} forceAdd ensure add is emitted
+ * @param {Number=} priorDepth Level of subdirectories already traversed.
+ * @returns {Promise<void>}
+ */
+async _addToFsEvents(path, transform, forceAdd, priorDepth) {
+  if (this.fsw.closed) {
+    return;
+  }
+  const opts = this.fsw.options;
+  const processPath = typeof transform === FUNCTION_TYPE ? transform : IDENTITY_FN;
+
+  const wh = this.fsw._getWatchHelpers(path);
+
+  // evaluate what is at the path we're being asked to watch
+  try {
+    const stats = await statMethods[wh.statMethod](wh.watchPath);
+    if (this.fsw.closed) return;
+    if (this.fsw._isIgnored(wh.watchPath, stats)) {
+      throw null;
+    }
+    if (stats.isDirectory()) {
+      // emit addDir unless this is a glob parent
+      if (!wh.globFilter) this.emitAdd(processPath(path), stats, processPath, opts, forceAdd);
+
+      // don't recurse further if it would exceed depth setting
+      if (priorDepth && priorDepth > opts.depth) return;
+
+      // scan the contents of the dir
+      this.fsw._readdirp(wh.watchPath, {
+        fileFilter: entry => wh.filterPath(entry),
+        directoryFilter: entry => wh.filterDir(entry),
+        ...Depth(opts.depth - (priorDepth || 0))
+      }).on(STR_DATA, (entry) => {
+        // need to check filterPath on dirs b/c filterDir is less restrictive
+        if (this.fsw.closed) {
+          return;
+        }
+        if (entry.stats.isDirectory() && !wh.filterPath(entry)) return;
+
+        const joinedPath = sysPath.join(wh.watchPath, entry.path);
+        const {fullPath} = entry;
+
+        if (wh.followSymlinks && entry.stats.isSymbolicLink()) {
+          // preserve the current depth here since it can't be derived from
+          // real paths past the symlink
+          const curDepth = opts.depth === undefined ?
+            undefined : calcDepth(joinedPath, sysPath.resolve(wh.watchPath)) + 1;
+
+          this._handleFsEventsSymlink(joinedPath, fullPath, processPath, curDepth);
+        } else {
+          this.emitAdd(joinedPath, entry.stats, processPath, opts, forceAdd);
+        }
+      }).on(EV_ERROR, EMPTY_FN).on(STR_END, () => {
+        this.fsw._emitReady();
+      });
+    } else {
+      this.emitAdd(wh.watchPath, stats, processPath, opts, forceAdd);
+      this.fsw._emitReady();
+    }
+  } catch (error) {
+    if (!error || this.fsw._handleError(error)) {
+      // TODO: Strange thing: "should not choke on an ignored watch path" will be failed without 2 ready calls -__-
+      this.fsw._emitReady();
+      this.fsw._emitReady();
+    }
+  }
+
+  if (opts.persistent && forceAdd !== true) {
+    if (typeof transform === FUNCTION_TYPE) {
+      // realpath has already been resolved
+      this.initWatch(undefined, path, wh, processPath);
+    } else {
+      let realPath;
+      try {
+        realPath = await realpath(wh.watchPath);
+      } catch (e) {}
+      this.initWatch(realPath, path, wh, processPath);
+    }
+  }
+}
+
+}
+
+module.exports = FsEventsHandler;
+module.exports.canUse = canUse;

node_modules/chokidar/lib/nodefs-handler.js

@@ -0,0 +1,654 @@
+'use strict';
+
+const fs = require('fs');
+const sysPath = require('path');
+const { promisify } = require('util');
+const isBinaryPath = require('is-binary-path');
+const {
+  isWindows,
+  isLinux,
+  EMPTY_FN,
+  EMPTY_STR,
+  KEY_LISTENERS,
+  KEY_ERR,
+  KEY_RAW,
+  HANDLER_KEYS,
+  EV_CHANGE,
+  EV_ADD,
+  EV_ADD_DIR,
+  EV_ERROR,
+  STR_DATA,
+  STR_END,
+  BRACE_START,
+  STAR
+} = require('./constants');
+
+const THROTTLE_MODE_WATCH = 'watch';
+
+const open = promisify(fs.open);
+const stat = promisify(fs.stat);
+const lstat = promisify(fs.lstat);
+const close = promisify(fs.close);
+const fsrealpath = promisify(fs.realpath);
+
+const statMethods = { lstat, stat };
+
+// TODO: emit errors properly. Example: EMFILE on Macos.
+const foreach = (val, fn) => {
+  if (val instanceof Set) {
+    val.forEach(fn);
+  } else {
+    fn(val);
+  }
+};
+
+const addAndConvert = (main, prop, item) => {
+  let container = main[prop];
+  if (!(container instanceof Set)) {
+    main[prop] = container = new Set([container]);
+  }
+  container.add(item);
+};
+
+const clearItem = cont => key => {
+  const set = cont[key];
+  if (set instanceof Set) {
+    set.clear();
+  } else {
+    delete cont[key];
+  }
+};
+
+const delFromSet = (main, prop, item) => {
+  const container = main[prop];
+  if (container instanceof Set) {
+    container.delete(item);
+  } else if (container === item) {
+    delete main[prop];
+  }
+};
+
+const isEmptySet = (val) => val instanceof Set ? val.size === 0 : !val;
+
+/**
+ * @typedef {String} Path
+ */
+
+// fs_watch helpers
+
+// object to hold per-process fs_watch instances
+// (may be shared across chokidar FSWatcher instances)
+
+/**
+ * @typedef {Object} FsWatchContainer
+ * @property {Set} listeners
+ * @property {Set} errHandlers
+ * @property {Set} rawEmitters
+ * @property {fs.FSWatcher=} watcher
+ * @property {Boolean=} watcherUnusable
+ */
+
+/**
+ * @type {Map<String,FsWatchContainer>}
+ */
+const FsWatchInstances = new Map();
+
+/**
+ * Instantiates the fs_watch interface
+ * @param {String} path to be watched
+ * @param {Object} options to be passed to fs_watch
+ * @param {Function} listener main event handler
+ * @param {Function} errHandler emits info about errors
+ * @param {Function} emitRaw emits raw event data
+ * @returns {fs.FSWatcher} new fsevents instance
+ */
+function createFsWatchInstance(path, options, listener, errHandler, emitRaw) {
+  const handleEvent = (rawEvent, evPath) => {
+    listener(path);
+    emitRaw(rawEvent, evPath, {watchedPath: path});
+
+    // emit based on events occurring for files from a directory's watcher in
+    // case the file's watcher misses it (and rely on throttling to de-dupe)
+    if (evPath && path !== evPath) {
+      fsWatchBroadcast(
+        sysPath.resolve(path, evPath), KEY_LISTENERS, sysPath.join(path, evPath)
+      );
+    }
+  };
+  try {
+    return fs.watch(path, options, handleEvent);
+  } catch (error) {
+    errHandler(error);
+  }
+}
+
+/**
+ * Helper for passing fs_watch event data to a collection of listeners
+ * @param {Path} fullPath absolute path bound to fs_watch instance
+ * @param {String} type listener type
+ * @param {*=} val1 arguments to be passed to listeners
+ * @param {*=} val2
+ * @param {*=} val3
+ */
+const fsWatchBroadcast = (fullPath, type, val1, val2, val3) => {
+  const cont = FsWatchInstances.get(fullPath);
+  if (!cont) return;
+  foreach(cont[type], (listener) => {
+    listener(val1, val2, val3);
+  });
+};
+
+/**
+ * Instantiates the fs_watch interface or binds listeners
+ * to an existing one covering the same file system entry
+ * @param {String} path
+ * @param {String} fullPath absolute path
+ * @param {Object} options to be passed to fs_watch
+ * @param {Object} handlers container for event listener functions
+ */
+const setFsWatchListener = (path, fullPath, options, handlers) => {
+  const {listener, errHandler, rawEmitter} = handlers;
+  let cont = FsWatchInstances.get(fullPath);
+
+  /** @type {fs.FSWatcher=} */
+  let watcher;
+  if (!options.persistent) {
+    watcher = createFsWatchInstance(
+      path, options, listener, errHandler, rawEmitter
+    );
+    return watcher.close.bind(watcher);
+  }
+  if (cont) {
+    addAndConvert(cont, KEY_LISTENERS, listener);
+    addAndConvert(cont, KEY_ERR, errHandler);
+    addAndConvert(cont, KEY_RAW, rawEmitter);
+  } else {
+    watcher = createFsWatchInstance(
+      path,
+      options,
+      fsWatchBroadcast.bind(null, fullPath, KEY_LISTENERS),
+      errHandler, // no need to use broadcast here
+      fsWatchBroadcast.bind(null, fullPath, KEY_RAW)
+    );
+    if (!watcher) return;
+    watcher.on(EV_ERROR, async (error) => {
+      const broadcastErr = fsWatchBroadcast.bind(null, fullPath, KEY_ERR);
+      cont.watcherUnusable = true; // documented since Node 10.4.1
+      // Workaround for https://github.com/joyent/node/issues/4337
+      if (isWindows && error.code === 'EPERM') {
+        try {
+          const fd = await open(path, 'r');
+          await close(fd);
+          broadcastErr(error);
+        } catch (err) {}
+      } else {
+        broadcastErr(error);
+      }
+    });
+    cont = {
+      listeners: listener,
+      errHandlers: errHandler,
+      rawEmitters: rawEmitter,
+      watcher
+    };
+    FsWatchInstances.set(fullPath, cont);
+  }
+  // const index = cont.listeners.indexOf(listener);
+
+  // removes this instance's listeners and closes the underlying fs_watch
+  // instance if there are no more listeners left
+  return () => {
+    delFromSet(cont, KEY_LISTENERS, listener);
+    delFromSet(cont, KEY_ERR, errHandler);
+    delFromSet(cont, KEY_RAW, rawEmitter);
+    if (isEmptySet(cont.listeners)) {
+      // Check to protect against issue gh-730.
+      // if (cont.watcherUnusable) {
+      cont.watcher.close();
+      // }
+      FsWatchInstances.delete(fullPath);
+      HANDLER_KEYS.forEach(clearItem(cont));
+      cont.watcher = undefined;
+      Object.freeze(cont);
+    }
+  };
+};
+
+// fs_watchFile helpers
+
+// object to hold per-process fs_watchFile instances
+// (may be shared across chokidar FSWatcher instances)
+const FsWatchFileInstances = new Map();
+
+/**
+ * Instantiates the fs_watchFile interface or binds listeners
+ * to an existing one covering the same file system entry
+ * @param {String} path to be watched
+ * @param {String} fullPath absolute path
+ * @param {Object} options options to be passed to fs_watchFile
+ * @param {Object} handlers container for event listener functions
+ * @returns {Function} closer
+ */
+const setFsWatchFileListener = (path, fullPath, options, handlers) => {
+  const {listener, rawEmitter} = handlers;
+  let cont = FsWatchFileInstances.get(fullPath);
+
+  /* eslint-disable no-unused-vars, prefer-destructuring */
+  let listeners = new Set();
+  let rawEmitters = new Set();
+
+  const copts = cont && cont.options;
+  if (copts && (copts.persistent < options.persistent || copts.interval > options.interval)) {
+    // "Upgrade" the watcher to persistence or a quicker interval.
+    // This creates some unlikely edge case issues if the user mixes
+    // settings in a very weird way, but solving for those cases
+    // doesn't seem worthwhile for the added complexity.
+    listeners = cont.listeners;
+    rawEmitters = cont.rawEmitters;
+    fs.unwatchFile(fullPath);
+    cont = undefined;
+  }
+
+  /* eslint-enable no-unused-vars, prefer-destructuring */
+
+  if (cont) {
+    addAndConvert(cont, KEY_LISTENERS, listener);
+    addAndConvert(cont, KEY_RAW, rawEmitter);
+  } else {
+    // TODO
+    // listeners.add(listener);
+    // rawEmitters.add(rawEmitter);
+    cont = {
+      listeners: listener,
+      rawEmitters: rawEmitter,
+      options,
+      watcher: fs.watchFile(fullPath, options, (curr, prev) => {
+        foreach(cont.rawEmitters, (rawEmitter) => {
+          rawEmitter(EV_CHANGE, fullPath, {curr, prev});
+        });
+        const currmtime = curr.mtimeMs;
+        if (curr.size !== prev.size || currmtime > prev.mtimeMs || currmtime === 0) {
+          foreach(cont.listeners, (listener) => listener(path, curr));
+        }
+      })
+    };
+    FsWatchFileInstances.set(fullPath, cont);
+  }
+  // const index = cont.listeners.indexOf(listener);
+
+  // Removes this instance's listeners and closes the underlying fs_watchFile
+  // instance if there are no more listeners left.
+  return () => {
+    delFromSet(cont, KEY_LISTENERS, listener);
+    delFromSet(cont, KEY_RAW, rawEmitter);
+    if (isEmptySet(cont.listeners)) {
+      FsWatchFileInstances.delete(fullPath);
+      fs.unwatchFile(fullPath);
+      cont.options = cont.watcher = undefined;
+      Object.freeze(cont);
+    }
+  };
+};
+
+/**
+ * @mixin
+ */
+class NodeFsHandler {
+
+/**
+ * @param {import("../index").FSWatcher} fsW
+ */
+constructor(fsW) {
+  this.fsw = fsW;
+  this._boundHandleError = (error) => fsW._handleError(error);
+}
+
+/**
+ * Watch file for changes with fs_watchFile or fs_watch.
+ * @param {String} path to file or dir
+ * @param {Function} listener on fs change
+ * @returns {Function} closer for the watcher instance
+ */
+_watchWithNodeFs(path, listener) {
+  const opts = this.fsw.options;
+  const directory = sysPath.dirname(path);
+  const basename = sysPath.basename(path);
+  const parent = this.fsw._getWatchedDir(directory);
+  parent.add(basename);
+  const absolutePath = sysPath.resolve(path);
+  const options = {persistent: opts.persistent};
+  if (!listener) listener = EMPTY_FN;
+
+  let closer;
+  if (opts.usePolling) {
+    options.interval = opts.enableBinaryInterval && isBinaryPath(basename) ?
+      opts.binaryInterval : opts.interval;
+    closer = setFsWatchFileListener(path, absolutePath, options, {
+      listener,
+      rawEmitter: this.fsw._emitRaw
+    });
+  } else {
+    closer = setFsWatchListener(path, absolutePath, options, {
+      listener,
+      errHandler: this._boundHandleError,
+      rawEmitter: this.fsw._emitRaw
+    });
+  }
+  return closer;
+}
+
+/**
+ * Watch a file and emit add event if warranted.
+ * @param {Path} file Path
+ * @param {fs.Stats} stats result of fs_stat
+ * @param {Boolean} initialAdd was the file added at watch instantiation?
+ * @returns {Function} closer for the watcher instance
+ */
+_handleFile(file, stats, initialAdd) {
+  if (this.fsw.closed) {
+    return;
+  }
+  const dirname = sysPath.dirname(file);
+  const basename = sysPath.basename(file);
+  const parent = this.fsw._getWatchedDir(dirname);
+  // stats is always present
+  let prevStats = stats;
+
+  // if the file is already being watched, do nothing
+  if (parent.has(basename)) return;
+
+  const listener = async (path, newStats) => {
+    if (!this.fsw._throttle(THROTTLE_MODE_WATCH, file, 5)) return;
+    if (!newStats || newStats.mtimeMs === 0) {
+      try {
+        const newStats = await stat(file);
+        if (this.fsw.closed) return;
+        // Check that change event was not fired because of changed only accessTime.
+        const at = newStats.atimeMs;
+        const mt = newStats.mtimeMs;
+        if (!at || at <= mt || mt !== prevStats.mtimeMs) {
+          this.fsw._emit(EV_CHANGE, file, newStats);
+        }
+        if (isLinux && prevStats.ino !== newStats.ino) {
+          this.fsw._closeFile(path)
+          prevStats = newStats;
+          this.fsw._addPathCloser(path, this._watchWithNodeFs(file, listener));
+        } else {
+          prevStats = newStats;
+        }
+      } catch (error) {
+        // Fix issues where mtime is null but file is still present
+        this.fsw._remove(dirname, basename);
+      }
+      // add is about to be emitted if file not already tracked in parent
+    } else if (parent.has(basename)) {
+      // Check that change event was not fired because of changed only accessTime.
+      const at = newStats.atimeMs;
+      const mt = newStats.mtimeMs;
+      if (!at || at <= mt || mt !== prevStats.mtimeMs) {
+        this.fsw._emit(EV_CHANGE, file, newStats);
+      }
+      prevStats = newStats;
+    }
+  }
+  // kick off the watcher
+  const closer = this._watchWithNodeFs(file, listener);
+
+  // emit an add event if we're supposed to
+  if (!(initialAdd && this.fsw.options.ignoreInitial) && this.fsw._isntIgnored(file)) {
+    if (!this.fsw._throttle(EV_ADD, file, 0)) return;
+    this.fsw._emit(EV_ADD, file, stats);
+  }
+
+  return closer;
+}
+
+/**
+ * Handle symlinks encountered while reading a dir.
+ * @param {Object} entry returned by readdirp
+ * @param {String} directory path of dir being read
+ * @param {String} path of this item
+ * @param {String} item basename of this item
+ * @returns {Promise<Boolean>} true if no more processing is needed for this entry.
+ */
+async _handleSymlink(entry, directory, path, item) {
+  if (this.fsw.closed) {
+    return;
+  }
+  const full = entry.fullPath;
+  const dir = this.fsw._getWatchedDir(directory);
+
+  if (!this.fsw.options.followSymlinks) {
+    // watch symlink directly (don't follow) and detect changes
+    this.fsw._incrReadyCount();
+
+    let linkPath;
+    try {
+      linkPath = await fsrealpath(path);
+    } catch (e) {
+      this.fsw._emitReady();
+      return true;
+    }
+
+    if (this.fsw.closed) return;
+    if (dir.has(item)) {
+      if (this.fsw._symlinkPaths.get(full) !== linkPath) {
+        this.fsw._symlinkPaths.set(full, linkPath);
+        this.fsw._emit(EV_CHANGE, path, entry.stats);
+      }
+    } else {
+      dir.add(item);
+      this.fsw._symlinkPaths.set(full, linkPath);
+      this.fsw._emit(EV_ADD, path, entry.stats);
+    }
+    this.fsw._emitReady();
+    return true;
+  }
+
+  // don't follow the same symlink more than once
+  if (this.fsw._symlinkPaths.has(full)) {
+    return true;
+  }
+
+  this.fsw._symlinkPaths.set(full, true);
+}
+
+_handleRead(directory, initialAdd, wh, target, dir, depth, throttler) {
+  // Normalize the directory name on Windows
+  directory = sysPath.join(directory, EMPTY_STR);
+
+  if (!wh.hasGlob) {
+    throttler = this.fsw._throttle('readdir', directory, 1000);
+    if (!throttler) return;
+  }
+
+  const previous = this.fsw._getWatchedDir(wh.path);
+  const current = new Set();
+
+  let stream = this.fsw._readdirp(directory, {
+    fileFilter: entry => wh.filterPath(entry),
+    directoryFilter: entry => wh.filterDir(entry),
+    depth: 0
+  }).on(STR_DATA, async (entry) => {
+    if (this.fsw.closed) {
+      stream = undefined;
+      return;
+    }
+    const item = entry.path;
+    let path = sysPath.join(directory, item);
+    current.add(item);
+
+    if (entry.stats.isSymbolicLink() && await this._handleSymlink(entry, directory, path, item)) {
+      return;
+    }
+
+    if (this.fsw.closed) {
+      stream = undefined;
+      return;
+    }
+    // Files that present in current directory snapshot
+    // but absent in previous are added to watch list and
+    // emit `add` event.
+    if (item === target || !target && !previous.has(item)) {
+      this.fsw._incrReadyCount();
+
+      // ensure relativeness of path is preserved in case of watcher reuse
+      path = sysPath.join(dir, sysPath.relative(dir, path));
+
+      this._addToNodeFs(path, initialAdd, wh, depth + 1);
+    }
+  }).on(EV_ERROR, this._boundHandleError);
+
+  return new Promise(resolve =>
+    stream.once(STR_END, () => {
+      if (this.fsw.closed) {
+        stream = undefined;
+        return;
+      }
+      const wasThrottled = throttler ? throttler.clear() : false;
+
+      resolve();
+
+      // Files that absent in current directory snapshot
+      // but present in previous emit `remove` event
+      // and are removed from @watched[directory].
+      previous.getChildren().filter((item) => {
+        return item !== directory &&
+          !current.has(item) &&
+          // in case of intersecting globs;
+          // a path may have been filtered out of this readdir, but
+          // shouldn't be removed because it matches a different glob
+          (!wh.hasGlob || wh.filterPath({
+            fullPath: sysPath.resolve(directory, item)
+          }));
+      }).forEach((item) => {
+        this.fsw._remove(directory, item);
+      });
+
+      stream = undefined;
+
+      // one more time for any missed in case changes came in extremely quickly
+      if (wasThrottled) this._handleRead(directory, false, wh, target, dir, depth, throttler);
+    })
+  );
+}
+
+/**
+ * Read directory to add / remove files from `@watched` list and re-read it on change.
+ * @param {String} dir fs path
+ * @param {fs.Stats} stats
+ * @param {Boolean} initialAdd
+ * @param {Number} depth relative to user-supplied path
+ * @param {String} target child path targeted for watch
+ * @param {Object} wh Common watch helpers for this path
+ * @param {String} realpath
+ * @returns {Promise<Function>} closer for the watcher instance.
+ */
+async _handleDir(dir, stats, initialAdd, depth, target, wh, realpath) {
+  const parentDir = this.fsw._getWatchedDir(sysPath.dirname(dir));
+  const tracked = parentDir.has(sysPath.basename(dir));
+  if (!(initialAdd && this.fsw.options.ignoreInitial) && !target && !tracked) {
+    if (!wh.hasGlob || wh.globFilter(dir)) this.fsw._emit(EV_ADD_DIR, dir, stats);
+  }
+
+  // ensure dir is tracked (harmless if redundant)
+  parentDir.add(sysPath.basename(dir));
+  this.fsw._getWatchedDir(dir);
+  let throttler;
+  let closer;
+
+  const oDepth = this.fsw.options.depth;
+  if ((oDepth == null || depth <= oDepth) && !this.fsw._symlinkPaths.has(realpath)) {
+    if (!target) {
+      await this._handleRead(dir, initialAdd, wh, target, dir, depth, throttler);
+      if (this.fsw.closed) return;
+    }
+
+    closer = this._watchWithNodeFs(dir, (dirPath, stats) => {
+      // if current directory is removed, do nothing
+      if (stats && stats.mtimeMs === 0) return;
+
+      this._handleRead(dirPath, false, wh, target, dir, depth, throttler);
+    });
+  }
+  return closer;
+}
+
+/**
+ * Handle added file, directory, or glob pattern.
+ * Delegates call to _handleFile / _handleDir after checks.
+ * @param {String} path to file or ir
+ * @param {Boolean} initialAdd was the file added at watch instantiation?
+ * @param {Object} priorWh depth relative to user-supplied path
+ * @param {Number} depth Child path actually targeted for watch
+ * @param {String=} target Child path actually targeted for watch
+ * @returns {Promise}
+ */
+async _addToNodeFs(path, initialAdd, priorWh, depth, target) {
+  const ready = this.fsw._emitReady;
+  if (this.fsw._isIgnored(path) || this.fsw.closed) {
+    ready();
+    return false;
+  }
+
+  const wh = this.fsw._getWatchHelpers(path, depth);
+  if (!wh.hasGlob && priorWh) {
+    wh.hasGlob = priorWh.hasGlob;
+    wh.globFilter = priorWh.globFilter;
+    wh.filterPath = entry => priorWh.filterPath(entry);
+    wh.filterDir = entry => priorWh.filterDir(entry);
+  }
+
+  // evaluate what is at the path we're being asked to watch
+  try {
+    const stats = await statMethods[wh.statMethod](wh.watchPath);
+    if (this.fsw.closed) return;
+    if (this.fsw._isIgnored(wh.watchPath, stats)) {
+      ready();
+      return false;
+    }
+
+    const follow = this.fsw.options.followSymlinks && !path.includes(STAR) && !path.includes(BRACE_START);
+    let closer;
+    if (stats.isDirectory()) {
+      const absPath = sysPath.resolve(path);
+      const targetPath = follow ? await fsrealpath(path) : path;
+      if (this.fsw.closed) return;
+      closer = await this._handleDir(wh.watchPath, stats, initialAdd, depth, target, wh, targetPath);
+      if (this.fsw.closed) return;
+      // preserve this symlink's target path
+      if (absPath !== targetPath && targetPath !== undefined) {
+        this.fsw._symlinkPaths.set(absPath, targetPath);
+      }
+    } else if (stats.isSymbolicLink()) {
+      const targetPath = follow ? await fsrealpath(path) : path;
+      if (this.fsw.closed) return;
+      const parent = sysPath.dirname(wh.watchPath);
+      this.fsw._getWatchedDir(parent).add(wh.watchPath);
+      this.fsw._emit(EV_ADD, wh.watchPath, stats);
+      closer = await this._handleDir(parent, stats, initialAdd, depth, path, wh, targetPath);
+      if (this.fsw.closed) return;
+
+      // preserve this symlink's target path
+      if (targetPath !== undefined) {
+        this.fsw._symlinkPaths.set(sysPath.resolve(path), targetPath);
+      }
+    } else {
+      closer = this._handleFile(wh.watchPath, stats, initialAdd);
+    }
+    ready();
+
+    this.fsw._addPathCloser(path, closer);
+    return false;
+
+  } catch (error) {
+    if (this.fsw._handleError(error)) {
+      ready();
+      return path;
+    }
+  }
+}
+
+}
+
+module.exports = NodeFsHandler;