Merge pull request #2 from faucet-pipeline/errors

Handle errors

.gitignore

@@ -1 +1,2 @@
 /node_modules
+/package-lock.json

README.md

@@ -11,10 +11,11 @@ ourselves. We simply use [chokidar](https://github.com/paulmillr/chokidar).
 Using nite-owl basically comes down to this:
 
 ```js
-let watch = require('nite-owl')
+let watch = require("nite-owl");
 
 watch(myFavoriteDirectory)
-    .on('edit', myFavoriteFunction)
+    .on("edit", myFavoriteFunction)
+    .on("error", myErrorFunction);
 ```
 
 Now, whenever something about the files in `myFavoriteDirectory` changes, the
@@ -24,6 +25,23 @@ This notification is debounced: You only get notified at most once every 50
 milliseconds. You can adjust that value by providing a second argument to the
 watch function.
 
+The error callback will be called, when watching the files resulted in an
+error. The most common error is the `TooManyFilesError` (it has the code
+`ERR_TOO_MANY_FILES`). It occurs on Linux when you watch too many files. In this
+case you have to either increase the inotify limits or choose to watch less
+files. An error handler could look like this:
+
+```js
+watch(myFavoriteDirectory).on("error", err => {
+	if(err.code === "ERR_TOO_MANY_FILES") {
+		console.error("Watching too many files");
+		process.exit(1);
+	} else {
+		throw err;
+	}
+});
+```
+
 ## License
 
 Licensed under Apache 2.0.

index.js

@@ -4,6 +4,13 @@ let chokidar = require("chokidar");
 let EventEmitter = require("events");
 let path = require("path");
 
+class TooManyFilesError extends Error {
+	constructor(...params) {
+		super(...params);
+		this.code = "ERR_TOO_MANY_FILES";
+	}
+};
+
 module.exports = (rootDirs, delay = 50) => {
 	if(!rootDirs.pop) {
 		rootDirs = [rootDirs];
@@ -21,6 +28,17 @@ module.exports = (rootDirs, delay = 50) => {
 		watcher.on("add", notify).
 			on("change", notify).
 			on("unlink", notify);
+	}).on("error", err => {
+		if(err.code === "ENOSPC") {
+			err = new TooManyFilesError("You are watching too many files");
+		}
+
+		// Emit the error if someone is listening. Otherwise throw it.
+		if(emitter.listenerCount("error") > 0) {
+			emitter.emit("error", err);
+		} else {
+			throw err;
+		}
 	});
 
 	return emitter;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "nite-owl",
-  "version": "3.1.0",
+  "version": "3.2.0",
   "description": "A debounced EventEmitter that watches for file changes",
   "main": "index.js",
   "scripts": {