From 0587510d194a78ea17d7c9d1f2447241c6f86b80 Mon Sep 17 00:00:00 2001
From: Jonathan Rudenberg <jonathan@titanous.com>
Date: Thu, 25 Dec 2014 20:59:31 -0500
Subject: [PATCH 1/2] Remove Close method from FileChanges

This method will never do what we want, closing the channels will always
signal receivers, which will confuse them.
---
 watch/filechanges.go | 6 ------
 watch/inotify.go     | 1 -
 watch/polling.go     | 2 --
 3 files changed, 9 deletions(-)

diff --git a/watch/filechanges.go b/watch/filechanges.go
index fb0f9ef..3ce5dce 100644
--- a/watch/filechanges.go
+++ b/watch/filechanges.go
@@ -23,12 +23,6 @@ func (fc *FileChanges) NotifyDeleted() {
 	sendOnlyIfEmpty(fc.Deleted)
 }
 
-func (fc *FileChanges) Close() {
-	close(fc.Modified)
-	close(fc.Truncated)
-	close(fc.Deleted)
-}
-
 // sendOnlyIfEmpty sends on a bool channel only if the channel has no
 // backlog to be read by other goroutines. This concurrency pattern
 // can be used to notify other goroutines if and only if they are
diff --git a/watch/inotify.go b/watch/inotify.go
index c2f13dc..0b1b1fe 100644
--- a/watch/inotify.go
+++ b/watch/inotify.go
@@ -77,7 +77,6 @@ func (fw *InotifyFileWatcher) ChangeEvents(t *tomb.Tomb, fi os.FileInfo) *FileCh
 
 	go func() {
 		defer inotifyTracker.CloseWatcher(w)
-		defer changes.Close()
 
 		for {
 			prevSize := fw.Size
diff --git a/watch/polling.go b/watch/polling.go
index 10a17eb..de01c71 100644
--- a/watch/polling.go
+++ b/watch/polling.go
@@ -49,8 +49,6 @@ func (fw *PollingFileWatcher) ChangeEvents(t *tomb.Tomb, origFi os.FileInfo) *Fi
 	fw.Size = origFi.Size()
 
 	go func() {
-		defer changes.Close()
-
 		var retry int = 0
 
 		prevSize := fw.Size

From 166cd27854c7ded9afb572098562750fb3533e67 Mon Sep 17 00:00:00 2001
From: Jonathan Rudenberg <jonathan@titanous.com>
Date: Wed, 24 Dec 2014 16:48:29 -0500
Subject: [PATCH 2/2] Add StopAtEOF to stop tailing when the end of the file is
 reached

---
 tail.go      | 23 ++++++++++++++++++++---
 tail_test.go | 19 +++++++++++++++++++
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/tail.go b/tail.go
index cedbb23..877f849 100644
--- a/tail.go
+++ b/tail.go
@@ -4,6 +4,7 @@ package tail
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"github.com/ActiveState/tail/ratelimiter"
 	"github.com/ActiveState/tail/util"
@@ -136,6 +137,14 @@ func (tail *Tail) Stop() error {
 	return tail.Wait()
 }
 
+// StopAtEOF stops tailing as soon as the end of the file is reached.
+func (tail *Tail) StopAtEOF() error {
+	tail.Kill(errStopAtEOF)
+	return tail.Wait()
+}
+
+var errStopAtEOF = errors.New("tail: stop at eof")
+
 func (tail *Tail) close() {
 	close(tail.Lines)
 	if tail.file != nil {
@@ -209,6 +218,8 @@ func (tail *Tail) tailFileSync() {
 
 	tail.openReader()
 
+	var stopAtEOF bool
+
 	// Read line by line.
 	for {
 		line, err := tail.readLine()
@@ -228,14 +239,16 @@ func (tail *Tail) tailFileSync() {
 				case <-tail.Dying():
 					return
 				}
-				err = tail.seekEnd()
-				if err != nil {
+				if err := tail.seekEnd(); err != nil {
 					tail.Kill(err)
 					return
 				}
 			}
+			if stopAtEOF && err == io.EOF {
+				return
+			}
 		} else if err == io.EOF {
-			if !tail.Follow {
+			if stopAtEOF || !tail.Follow {
 				return
 			}
 			// When EOF is reached, wait for more data to become
@@ -256,6 +269,10 @@ func (tail *Tail) tailFileSync() {
 
 		select {
 		case <-tail.Dying():
+			if tail.Err() == errStopAtEOF {
+				stopAtEOF = true
+				continue
+			}
 			return
 		default:
 		}
diff --git a/tail_test.go b/tail_test.go
index 0b9c5f9..f7abe37 100644
--- a/tail_test.go
+++ b/tail_test.go
@@ -54,6 +54,25 @@ func TestStop(t *testing.T) {
 	Cleanup()
 }
 
+func TestStopAtEOF(_t *testing.T) {
+	t := NewTailTest("maxlinesize", _t)
+	t.CreateFile("test.txt", "hello\nthere\nworld\n")
+	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil})
+
+	// read "hello"
+	<-tail.Lines
+
+	done := make(chan struct{})
+	go func() {
+		<-time.After(100 * time.Millisecond)
+		t.VerifyTailOutput(tail, []string{"there", "world"})
+		close(done)
+	}()
+	tail.StopAtEOF()
+	<-done
+	Cleanup()
+}
+
 func TestMaxLineSize(_t *testing.T) {
 	t := NewTailTest("maxlinesize", _t)
 	t.CreateFile("test.txt", "hello\nworld\nfin\nhe")