From 2a8606bd9816b13782247aa9ed42610c0e90ccbf Mon Sep 17 00:00:00 2001
From: James Shubin <james@shubin.ca>
Date: Mon, 13 Feb 2017 15:24:36 -0500
Subject: [PATCH] recwatch: Close cleanly after Watcher finishes

This cleans up the recwatch code to avoid some possible races. While you
were previously able to call Close more than once, this was really
something that would mask bugs, rather than a useful feature.
---
 recwatch/recwatch.go | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/recwatch/recwatch.go b/recwatch/recwatch.go
index 451bdf38..8029d5ec 100644
--- a/recwatch/recwatch.go
+++ b/recwatch/recwatch.go
@@ -53,10 +53,8 @@ type RecWatcher struct {
 	events   chan Event // one channel for events and err...
 	closed   bool       // is the events channel closed?
 	mutex    sync.Mutex // lock guarding the channel closing
-	once     sync.Once
 	wg       sync.WaitGroup
 	exit     chan struct{}
-	closeErr error
 }
 
 // NewRecWatcher creates an initializes a new recursive watcher.
@@ -89,7 +87,9 @@ func (obj *RecWatcher) Init() error {
 		}
 	}
 
+	obj.wg.Add(1)
 	go func() {
+		defer obj.wg.Done()
 		if err := obj.Watch(); err != nil {
 			// we need this mutex, because if we Init and then Close
 			// immediately, this can send after closed which panics!
@@ -99,7 +99,6 @@ func (obj *RecWatcher) Init() error {
 			}
 			obj.mutex.Unlock()
 		}
-		obj.Close()
 	}()
 	return nil
 }
@@ -114,13 +113,6 @@ func (obj *RecWatcher) Init() error {
 
 // Close shuts down the watcher.
 func (obj *RecWatcher) Close() error {
-	obj.once.Do(obj.close) // don't cause the channel to close twice
-	return obj.closeErr
-}
-
-// This close function is the function that actually does the close work. Don't
-// call it more than once!
-func (obj *RecWatcher) close() {
 	var err error
 	close(obj.exit) // send exit signal
 	obj.wg.Wait()
@@ -132,11 +124,11 @@ func (obj *RecWatcher) close() {
 		//	obj.events <- Event{Error: err}
 		//}
 	}
-	obj.mutex.Lock()
+	obj.mutex.Lock() // FIXME: I don't think this mutex is needed anymore...
 	obj.closed = true
 	close(obj.events)
 	obj.mutex.Unlock()
-	obj.closeErr = err // set the error
+	return err
 }
 
 // Events returns a channel of events. These include events for errors.
@@ -147,8 +139,6 @@ func (obj *RecWatcher) Watch() error {
 	if obj.watcher == nil {
 		return fmt.Errorf("Watcher is not initialized!")
 	}
-	obj.wg.Add(1)
-	defer obj.wg.Done()
 
 	patharray := util.PathSplit(obj.safename) // tokenize the path
 	var index = len(patharray)                // starting index