Follow symlinks

Solves webpack#231 and updates the README to match.

README.md

@@ -19,7 +19,6 @@ watchpack high level API doesn't map directly to watchers. Instead a three level
 - The real watchers are created by the `DirectoryWatcher`.
 - Files are never watched directly. This should keep the watcher count low.
 - Watching can be started in the past. This way watching can start after file reading.
-- Symlinks are not followed, instead the symlink is watched.
 
 ## API
 

lib/DirectoryWatcher.js

@@ -392,7 +392,8 @@ class DirectoryWatcher extends EventEmitter {
 			const checkStats = () => {
 				if (this.closed) return;
 				this._activeEvents.set(filename, false);
-				fs.lstat(filePath, (err, stats) => {
+
+				const handleStats = (err, stats) => {
 					if (this.closed) return;
 					if (this._activeEvents.get(filename) === true) {
 						process.nextTick(checkStats);
@@ -438,8 +439,15 @@ class DirectoryWatcher extends EventEmitter {
 							false,
 							eventType
 						);
+						if (
+							this.watcherManager.options.followSymlinks &&
+							stats.isSymbolicLink()
+						) {
+							fs.stat(filePath, handleStats);
+						}
 					}
-				});
+				};
+				fs.lstat(filePath, handleStats);
 			};
 			process.nextTick(checkStats);
 		} else {
@@ -625,7 +633,7 @@ class DirectoryWatcher extends EventEmitter {
 					}
 				});
 				for (const itemPath of itemPaths) {
-					fs.lstat(itemPath, (err2, stats) => {
+					const handleStats = (err2, stats) => {
 						if (this.closed) return;
 						if (err2) {
 							if (
@@ -652,6 +660,12 @@ class DirectoryWatcher extends EventEmitter {
 								true,
 								"scan (file)"
 							);
+							if (
+								this.watcherManager.options.followSymlinks &&
+								stats.isSymbolicLink()
+							) {
+								fs.stat(itemPath, handleStats);
+							}
 						} else if (stats.isDirectory()) {
 							if (!initial || !this.directories.has(itemPath))
 								this.setDirectory(
@@ -662,7 +676,8 @@ class DirectoryWatcher extends EventEmitter {
 								);
 						}
 						itemFinished();
-					});
+					};
+					fs.lstat(itemPath, handleStats);
 				}
 				itemFinished();
 			});