Bump go directive and modernize stdlib usage

Raise the go directive to 1.21.0 so it is consistent with the
toolchain go1.26.0 directive; the previous go 1.13 caused the vet
inlining analyzer to report spurious diagnostics under a modern
toolchain.

With a current language version the deprecated APIs are now flagged,
so replace them with their supported equivalents:

- io/ioutil -> os (ReadDir, ReadFile, WriteFile)
- reflect.Ptr -> reflect.Pointer

Also fold in small cleanups surfaced along the way: use
strings.TrimSuffix, add //go:build constraints, drop an unused test
helper, and tighten test file permissions to 0600.

Signed-off-by: Antonin Bas <antonin.bas@broadcom.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: antoninbas

chown.go

@@ -1,3 +1,4 @@
+//go:build !linux
 // +build !linux
 
 package lumberjack

go.mod

@@ -1,5 +1,5 @@
 module gopkg.in/natefinch/lumberjack.v2
 
-go 1.13
+go 1.21.0
 
 toolchain go1.26.0

linux_test.go

@@ -1,3 +1,4 @@
+//go:build linux
 // +build linux
 
 package lumberjack

lumberjack.go

@@ -3,7 +3,7 @@
 // Note that this is v2.0 of lumberjack, and should be imported using gopkg.in
 // thusly:
 //
-//   import "gopkg.in/natefinch/lumberjack.v2"
+//	import "gopkg.in/natefinch/lumberjack.v2"
 //
 // The package name remains simply lumberjack, and the code resides at
 // https://github.com/natefinch/lumberjack under the v2.0 branch.
@@ -26,7 +26,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"sort"
@@ -66,7 +65,7 @@ var _ io.WriteCloser = (*Logger)(nil)
 // `/var/log/foo/server.log`, a backup created at 6:30pm on Nov 11 2016 would
 // use the filename `/var/log/foo/server-2016-11-04T18-30-00.000.log`
 //
-// Cleaning Up Old Log Files
+// # Cleaning Up Old Log Files
 //
 // Whenever a new logfile gets created, old log files may be deleted.  The most
 // recent files according to the encoded timestamp will be retained, up to a
@@ -331,10 +330,7 @@ func (l *Logger) millRunOnce() error {
 		for _, f := range files {
 			// Only count the uncompressed log file or the
 			// compressed log file, not both.
-			fn := f.Name()
-			if strings.HasSuffix(fn, compressSuffix) {
-				fn = fn[:len(fn)-len(compressSuffix)]
-			}
+			fn := strings.TrimSuffix(f.Name(), compressSuffix)
 			preserved[fn] = true
 
 			if len(preserved) > l.MaxBackups {
@@ -450,24 +446,29 @@ func (l *Logger) stopMill() {
 // oldLogFiles returns the list of backup log files stored in the same
 // directory as the current log file, sorted by ModTime
 func (l *Logger) oldLogFiles() ([]logInfo, error) {
-	files, err := ioutil.ReadDir(l.dir())
+	entries, err := os.ReadDir(l.dir())
 	if err != nil {
 		return nil, fmt.Errorf("can't read log file directory: %s", err)
 	}
 	logFiles := []logInfo{}
 
 	prefix, ext := l.prefixAndExt()
 
-	for _, f := range files {
-		if f.IsDir() {
+	for _, e := range entries {
+		if e.IsDir() {
+			continue
+		}
+		info, err := e.Info()
+		if err != nil {
+			// The file may have been removed since ReadDir listed it.
 			continue
 		}
-		if t, err := l.timeFromName(f.Name(), prefix, ext); err == nil {
-			logFiles = append(logFiles, logInfo{t, f})
+		if t, err := l.timeFromName(info.Name(), prefix, ext); err == nil {
+			logFiles = append(logFiles, logInfo{t, info})
 			continue
 		}
-		if t, err := l.timeFromName(f.Name(), prefix, ext+compressSuffix); err == nil {
-			logFiles = append(logFiles, logInfo{t, f})
+		if t, err := l.timeFromName(info.Name(), prefix, ext+compressSuffix); err == nil {
+			logFiles = append(logFiles, logInfo{t, info})
 			continue
 		}
 		// error parsing means that the suffix at the end was not generated

lumberjack_test.go

@@ -5,7 +5,6 @@ import (
 	"compress/gzip"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -63,7 +62,7 @@ func TestOpenExisting(t *testing.T) {
 
 	filename := logFile(dir)
 	data := []byte("foo!")
-	err := ioutil.WriteFile(filename, data, 0644)
+	err := os.WriteFile(filename, data, 0600)
 	isNil(err, t)
 	existsWithContent(filename, data, t)
 
@@ -188,7 +187,7 @@ func TestFirstWriteRotate(t *testing.T) {
 	defer l.Close()
 
 	start := []byte("boooooo!")
-	err := ioutil.WriteFile(filename, start, 0600)
+	err := os.WriteFile(filename, start, 0600)
 	isNil(err, t)
 
 	newFakeTime()
@@ -277,7 +276,7 @@ func TestMaxBackups(t *testing.T) {
 	// create a file that is close to but different from the logfile name.
 	// It shouldn't get caught by our deletion filters.
 	notlogfile := logFile(dir) + ".foo"
-	err = ioutil.WriteFile(notlogfile, []byte("data"), 0644)
+	err = os.WriteFile(notlogfile, []byte("data"), 0600)
 	isNil(err, t)
 
 	// Make a directory that exactly matches our log file filters... it still
@@ -295,7 +294,7 @@ func TestMaxBackups(t *testing.T) {
 	// not be counted since both the compressed and the uncompressed
 	// log files still exist.
 	compLogFile := fourthFilename + compressSuffix
-	err = ioutil.WriteFile(compLogFile, []byte("compress"), 0644)
+	err = os.WriteFile(compLogFile, []byte("compress"), 0600)
 	isNil(err, t)
 
 	// this will make us rotate again
@@ -344,24 +343,24 @@ func TestCleanupExistingBackups(t *testing.T) {
 
 	data := []byte("data")
 	backup := backupFile(dir)
-	err := ioutil.WriteFile(backup, data, 0644)
+	err := os.WriteFile(backup, data, 0600)
 	isNil(err, t)
 
 	newFakeTime()
 
 	backup = backupFile(dir)
-	err = ioutil.WriteFile(backup+compressSuffix, data, 0644)
+	err = os.WriteFile(backup+compressSuffix, data, 0600)
 	isNil(err, t)
 
 	newFakeTime()
 
 	backup = backupFile(dir)
-	err = ioutil.WriteFile(backup, data, 0644)
+	err = os.WriteFile(backup, data, 0600)
 	isNil(err, t)
 
 	// now create a primary log file with some data
 	filename := logFile(dir)
-	err = ioutil.WriteFile(filename, data, 0644)
+	err = os.WriteFile(filename, data, 0600)
 	isNil(err, t)
 
 	l := &Logger{
@@ -462,7 +461,7 @@ func TestOldLogFiles(t *testing.T) {
 
 	filename := logFile(dir)
 	data := []byte("data")
-	err := ioutil.WriteFile(filename, data, 07)
+	err := os.WriteFile(filename, data, 0600)
 	isNil(err, t)
 
 	// This gives us a time with the same precision as the time we get from the
@@ -471,7 +470,7 @@ func TestOldLogFiles(t *testing.T) {
 	isNil(err, t)
 
 	backup := backupFile(dir)
-	err = ioutil.WriteFile(backup, data, 07)
+	err = os.WriteFile(backup, data, 0600)
 	isNil(err, t)
 
 	newFakeTime()
@@ -480,7 +479,7 @@ func TestOldLogFiles(t *testing.T) {
 	isNil(err, t)
 
 	backup2 := backupFile(dir)
-	err = ioutil.WriteFile(backup2, data, 07)
+	err = os.WriteFile(backup2, data, 0600)
 	isNil(err, t)
 
 	l := &Logger{Filename: filename}
@@ -666,9 +665,9 @@ func TestCompressOnResume(t *testing.T) {
 	// Create a backup file and empty "compressed" file.
 	filename2 := backupFile(dir)
 	b := []byte("foo!")
-	err := ioutil.WriteFile(filename2, b, 0644)
+	err := os.WriteFile(filename2, b, 0600)
 	isNil(err, t)
-	err = ioutil.WriteFile(filename2+compressSuffix, []byte{}, 0644)
+	err = os.WriteFile(filename2+compressSuffix, []byte{}, 0600)
 	isNil(err, t)
 
 	newFakeTime()
@@ -814,7 +813,7 @@ func TestMillRunDrainsPendingRequestBeforeStop(t *testing.T) {
 		}
 		// Pre-create a backup that the mill is expected to compress.
 		backup := backupFile(dir)
-		err := ioutil.WriteFile(backup, []byte("content"), 0644)
+		err := os.WriteFile(backup, []byte("content"), 0600)
 		isNil(err, t)
 
 		l.millCh = make(chan bool, 1)
@@ -848,7 +847,7 @@ func existsWithContent(path string, content []byte, t testing.TB) {
 	isNilUp(err, t, 1)
 	equalsUp(int64(len(content)), info.Size(), t, 1)
 
-	b, err := ioutil.ReadFile(path)
+	b, err := os.ReadFile(path)
 	isNilUp(err, t, 1)
 	equalsUp(content, b, t, 1)
 }
@@ -867,15 +866,9 @@ func backupFileLocal(dir string) string {
 	return filepath.Join(dir, "foobar-"+fakeTime().Format(backupTimeFormat)+".log")
 }
 
-// logFileLocal returns the log file name in the given directory for the current
-// fake time using the local timezone.
-func logFileLocal(dir string) string {
-	return filepath.Join(dir, fakeTime().Format(backupTimeFormat))
-}
-
 // fileCount checks that the number of files in the directory is exp.
 func fileCount(dir string, exp int, t testing.TB) {
-	files, err := ioutil.ReadDir(dir)
+	files, err := os.ReadDir(dir)
 	isNilUp(err, t, 1)
 	// Make sure no other files were created.
 	equalsUp(exp, len(files), t, 1)

rotate_test.go

@@ -1,3 +1,4 @@
+//go:build linux
 // +build linux
 
 package lumberjack

testing_test.go

@@ -83,7 +83,7 @@ func _isNil(obtained interface{}) bool {
 	}
 
 	switch v := reflect.ValueOf(obtained); v.Kind() {
-	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Pointer, reflect.Slice:
 		return v.IsNil()
 	}