use chokidar 2 or 3 depending on node.js version

chokidar2/index.js

@@ -0,0 +1 @@
+module.exports = require("chokidar");

chokidar2/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "chokidar2",
+  "version": "2.0.0",
+  "private": true,
+  "engines": {
+    "node": "<8.10.0"
+  },
+  "dependencies": {
+    "chokidar": "^2.1.8"
+  }
+}

lib/DirectoryWatcher.js

@@ -6,7 +6,7 @@
 
 var EventEmitter = require("events").EventEmitter;
 var async = require("neo-async");
-var chokidar = require("chokidar");
+var chokidar = require("./chokidar");
 var fs = require("graceful-fs");
 var path = require("path");
 
@@ -357,7 +357,8 @@ DirectoryWatcher.prototype.getTimes = function() {
 
 DirectoryWatcher.prototype.close = function() {
 	this.initialScan = false;
-	this.watcher.close().catch(this.onWatcherError.bind(this));
+	var p = this.watcher.close();
+	if(p && p.catch) p.catch(this.onWatcherError.bind(this));
 	if(this.nestedWatching) {
 		Object.keys(this.directories).forEach(function(dir) {
 			this.directories[dir].close();

lib/chokidar.js

@@ -0,0 +1,22 @@
+var v3Err;
+try {
+	module.exports = require("chokidar");
+	return;
+} catch(e) {
+	v3Err = e;
+}
+
+var v2Err;
+try {
+	module.exports = require("chokidar2");
+	return;
+} catch(e) {
+	v2Err = e;
+}
+
+throw new Error(
+	"No version of chokidar is available. Tried chokidar@2 and chokidar@3.\n" +
+	"You could try to manually install any chokidar version.\n" +
+	"chokidar@3: " + v3Err + "\n" +
+	"chokidar@2: " + v2Err + "\n"
+)

package.json

@@ -36,8 +36,11 @@
     "rimraf": "^2.6.2",
     "should": "^8.3.1"
   },
-  "dependencies": {
+  "optionalDependencies": {
     "chokidar": "^3.3.0",
+    "chokidar2": "file:./chokidar2"
+  },
+  "dependencies": {
     "graceful-fs": "^4.1.2",
     "neo-async": "^2.5.0"
   },

test/Assumption.js

@@ -4,7 +4,7 @@
 require("should");
 var path = require("path");
 var fs = require("fs");
-var chokidar = require("chokidar");
+var chokidar = require("../lib/chokidar");
 var TestHelper = require("./helpers/TestHelper");
 var Watchpack = require("../lib/watchpack");