replace the alarmist panic with Fatal

Fatal shows only a single goroutine stacktrace.

tail.go

@@ -5,6 +5,7 @@ package tail
 import (
 	"bufio"
 	"fmt"
+	"github.com/ActiveState/tail/util"
 	"github.com/ActiveState/tail/watch"
 	"io"
 	"launchpad.net/tomb"
@@ -63,7 +64,7 @@ type Tail struct {
 // `Lines` channel.
 func TailFile(filename string, config Config) (*Tail, error) {
 	if config.ReOpen && !config.Follow {
-		panic("cannot set ReOpen without Follow.")
+		util.Fatal("cannot set ReOpen without Follow.")
 	}
 
 	t := &Tail{
@@ -286,7 +287,7 @@ func (tail *Tail) sendLine(line []byte) bool {
 
 	// Split longer lines
 	if tail.MaxLineSize > 0 && len(line) > tail.MaxLineSize {
-		lines = partitionString(
+		lines = util.PartitionString(
 			string(line), tail.MaxLineSize)
 	}
 

util/util.go

@@ -1,10 +1,30 @@
 // Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
 
-package tail
+package util
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"runtime/debug"
+)
+
+type Logger struct {
+	*log.Logger
+}
+
+var LOGGER = &Logger{log.New(os.Stderr, "", log.LstdFlags)}
+
+// fatal is like panic except it displays only the current goroutine's stack.
+func Fatal(format string, v ...interface{}) {
+	// https://github.com/ActiveState/log/blob/master/log.go#L45
+	LOGGER.Output(2, fmt.Sprintf("FATAL -- "+format, v...)+"\n"+string(debug.Stack()))
+	os.Exit(1)
+}
 
 // partitionString partitions the string into chunks of given size,
 // with the last chunk of variable size.
-func partitionString(s string, chunkSize int) []string {
+func PartitionString(s string, chunkSize int) []string {
 	if chunkSize <= 0 {
 		panic("invalid chunkSize")
 	}

watch/inotify.go

@@ -3,6 +3,7 @@
 package watch
 
 import (
+	"github.com/ActiveState/tail/util"
 	"github.com/howeyc/fsnotify"
 	"launchpad.net/tomb"
 	"os"
@@ -61,11 +62,11 @@ func (fw *InotifyFileWatcher) ChangeEvents(t *tomb.Tomb, fi os.FileInfo) *FileCh
 
 	w, err := fsnotify.NewWatcher()
 	if err != nil {
-		panic(err)
+		util.Fatal("Error creating fsnotify watcher: %v", err)
 	}
 	err = w.Watch(fw.Filename)
 	if err != nil {
-		panic(err)
+		util.Fatal("Error watching %v: %v", fw.Filename, err)
 	}
 
 	fw.Size = fi.Size()
@@ -101,8 +102,8 @@ func (fw *InotifyFileWatcher) ChangeEvents(t *tomb.Tomb, fi os.FileInfo) *FileCh
 						changes.NotifyDeleted()
 						return
 					}
-					// XXX: no panic here
+					// XXX: report this error back to the user
-					panic(err)
+					util.Fatal("Failed to stat file %v: %v", fw.Filename, err)
 				}
 				fw.Size = fi.Size()
 

watch/polling.go

@@ -3,6 +3,7 @@
 package watch
 
 import (
+	"github.com/ActiveState/tail/util"
 	"launchpad.net/tomb"
 	"os"
 	"time"
@@ -43,7 +44,7 @@ func (fw *PollingFileWatcher) ChangeEvents(t *tomb.Tomb, origFi os.FileInfo) *Fi
 	var prevModTime time.Time
 
 	// XXX: use tomb.Tomb to cleanly manage these goroutines. replace
-	// the panic (below) with tomb's Kill.
+	// the fatal (below) with tomb's Kill.
 
 	fw.Size = origFi.Size()
 
@@ -66,8 +67,8 @@ func (fw *PollingFileWatcher) ChangeEvents(t *tomb.Tomb, origFi os.FileInfo) *Fi
 					changes.NotifyDeleted()
 					return
 				}
-				/// XXX: do not panic here.
+				// XXX: report this error back to the user
-				panic(err)
+				util.Fatal("Failed to stat file %v: %v", fw.Filename, err)
 			}
 
 			// File got moved/renamed?