lint: add golangci-lint error and fix errors

backend.go

@@ -4,13 +4,14 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path/filepath"
 )
 
 // Backend is the interface that specifies the methods that a backend must
-// implement
+// implement.
 type Backend interface {
 	Write(*Record) error
-	SetFormatter(*Formatter)
+	SetFormatter(Formatter)
 	SetLevel(Level)
 	Level() Level
 	Reopen() error
@@ -23,86 +24,86 @@ type Backend interface {
 
 // FileBackend is a backend that writes to a file.
 type FileBackend struct {
+	formatter Formatter
 	l         io.Writer
-	formatter *Formatter
-	level     Level
 	filepath  string
+	level     Level
 }
 
 // NewStdoutBackend creates a new backend to write the logs on the standard
-// output
-func NewStdoutBackend() (b *FileBackend) {
-	b = &FileBackend{
+// output.
+func NewStdoutBackend() *FileBackend {
+	return &FileBackend{
 		l:         os.Stdout,
-		formatter: &defaultFormatter,
+		formatter: defaultFormatter,
 	}
-	return
 }
 
-// NewStderrBackend creates a new backend to write the logs on the error output
-func NewStderrBackend() (b *FileBackend) {
-	b = &FileBackend{
+// NewStderrBackend creates a new backend to write the logs on the error output.
+func NewStderrBackend() *FileBackend {
+	return &FileBackend{
 		l:         os.Stderr,
-		formatter: &defaultFormatter,
+		formatter: defaultFormatter,
 	}
-	return
 }
 
-// NewFileBackend creates a new backend to write the logs in a given file
+// NewFileBackend creates a new backend to write the logs in a given file.
 func NewFileBackend(filename string) (*FileBackend, error) {
-	fd, err := os.OpenFile(filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0644) //nolint: gosec
+	fd, err := os.OpenFile(filepath.Clean(filename),
+		os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0o600)
 	if err != nil {
-		return nil, fmt.Errorf("Cannot open log file %s: %w", filename, err)
+		return nil, fmt.Errorf("cannot open log file %s: %w", filename, err)
 	}
 
 	b := &FileBackend{
 		l:         fd,
-		formatter: &defaultFormatter,
+		formatter: defaultFormatter,
 		filepath:  filename,
 	}
 
 	return b, nil
 }
 
-// NewIoBackend creates a new backend to write the logs in a given io.Writer
-func NewIoBackend(buf io.Writer) (b *FileBackend) {
+// NewIoBackend creates a new backend to write the logs in a given io.Writer.
+func NewIoBackend(buf io.Writer) *FileBackend {
 	return &FileBackend{
 		l:         buf,
-		formatter: &defaultFormatter,
+		formatter: defaultFormatter,
 	}
 }
 
 func (b FileBackend) Write(r *Record) error {
-	text := (*b.formatter)(r)
+	text := b.formatter(r)
 	_, err := io.WriteString(b.l, text)
-	return err
+
+	return fmt.Errorf("cannot write logs: %w", err)
 }
 
-// SetLevel changes the log level of the backend
+// SetLevel changes the log level of the backend.
 func (b *FileBackend) SetLevel(l Level) {
 	b.level = l
 }
 
-// Level returns the log level set for this backend
+// Level returns the log level set for this backend.
 func (b *FileBackend) Level() Level {
 	return b.level
 }
 
-// SetFormatter defines the formatter for this backend
-func (b *FileBackend) SetFormatter(f *Formatter) {
+// SetFormatter defines the formatter for this backend.
+func (b *FileBackend) SetFormatter(f Formatter) {
 	b.formatter = f
 }
 
 // Reopen closes and reopens the file it writes to. It should be used after log
-// rotation
+// rotation.
 func (b *FileBackend) Reopen() error {
 	if err := b.Close(); err != nil {
 		return err
 	}
 
-	fd, err := os.OpenFile(b.filepath, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0644) //nolint: gosec
+	fd, err := os.OpenFile(b.filepath, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0o600)
 	if err != nil {
-		return fmt.Errorf("Cannot open log file %s: %w", b.filepath, err)
+		return fmt.Errorf("cannot open log file %s: %w", b.filepath, err)
 	}
 
 	b.l = fd
@@ -110,7 +111,7 @@ func (b *FileBackend) Reopen() error {
 	return nil
 }
 
-// Close closes the underlying file used by the backend
+// Close closes the underlying file used by the backend.
 func (b *FileBackend) Close() error {
 	if b.filepath == "" {
 		return nil
@@ -118,7 +119,7 @@ func (b *FileBackend) Close() error {
 
 	if c, ok := b.l.(io.Closer); ok {
 		if err := c.Close(); err != nil {
-			return err
+			return fmt.Errorf("cannot close log file: %w", err)
 		}
 	}
 
@@ -129,36 +130,36 @@ func (b *FileBackend) Close() error {
 // Noop Backend
 //
 
-// NoopBackend does nothing and discards all log entries without writing them anywhere
+// NoopBackend does nothing and discards all log entries without writing them anywhere.
 type NoopBackend struct{}
 
-// NewNoopBackend creates a noop backend
-func NewNoopBackend() (Backend, error) {
+// NewNoopBackend creates a noop backend.
+func NewNoopBackend() (*NoopBackend, error) {
 	return &NoopBackend{}, nil
 }
 
-// Write is a noop
-func (nb *NoopBackend) Write(r *Record) error {
+// Write is a noop.
+func (*NoopBackend) Write(_ *Record) error {
 	return nil
 }
 
-// SetFormatter is a noop
-func (nb *NoopBackend) SetFormatter(f *Formatter) {}
+// SetFormatter is a noop.
+func (*NoopBackend) SetFormatter(_ *Formatter) {}
 
-// SetLevel is a noop
-func (nb *NoopBackend) SetLevel(level Level) {}
+// SetLevel is a noop.
+func (*NoopBackend) SetLevel(_ Level) {}
 
-// Level always returns DefeultLevel
-func (nb *NoopBackend) Level() Level {
+// Level always returns DefeultLevel.
+func (*NoopBackend) Level() Level {
 	return DefaultLevel
 }
 
-// Reopen is a noop
-func (nb *NoopBackend) Reopen() error {
+// Reopen is a noop.
+func (*NoopBackend) Reopen() error {
 	return nil
 }
 
-// Close is a noop
-func (nb *NoopBackend) Close() error {
+// Close is a noop.
+func (*NoopBackend) Close() error {
 	return nil
 }

backend_syslog_linux.go

@@ -1,46 +1,56 @@
+//go:build !windows && !nacl && !plan9
 // +build !windows,!nacl,!plan9
 
 package logging
 
 import (
+	"errors"
 	"fmt"
 	"log/syslog"
 	"strings"
 )
 
+var errUnknownFacility = errors.New("unknown facility")
+
 //
 // Syslog Backend
 //
 
-// SyslogBackend writes the logs to a syslog system
+// SyslogBackend writes the logs to a syslog system.
 type SyslogBackend struct {
 	w         *syslog.Writer
-	formatter *Formatter
+	formatter Formatter
 	level     Level
 }
 
 // NewSyslogBackend initializes a new connection to a syslog server with the
 // given facility.
 // tag can contain an identifier for the log stream. It defaults to os.Arg[0].
-func NewSyslogBackend(facilityName string, tag string) (Backend, error) {
+func NewSyslogBackend(facilityName, tag string) (*SyslogBackend, error) {
 	f, err := facility(facilityName)
 	if err != nil {
 		return nil, err
 	}
+
 	w, err := syslog.New(f, tag)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("cannot initialize syslog: %w", err)
 	}
+
 	sb := &SyslogBackend{
 		w:         w,
-		formatter: &basicFormatter,
+		formatter: basicFormatter,
 	}
+
 	return sb, nil
 }
 
-// Write sends an entry to the syslog server
-func (sb *SyslogBackend) Write(r *Record) (err error) {
-	text := (*sb.formatter)(r)
+// Write sends an entry to the syslog server.
+func (sb *SyslogBackend) Write(r *Record) error {
+	var err error
+
+	text := sb.formatter(r)
+
 	switch r.Level {
 	case Debug:
 		err = sb.w.Debug(text)
@@ -55,34 +65,40 @@ func (sb *SyslogBackend) Write(r *Record) (err error) {
 	case Fatal:
 		err = sb.w.Emerg(text)
 	}
-	return err
+
+	return fmt.Errorf("cannot log to syslog: %w", err)
 }
 
-// SetFormatter defines the formatter for this backend
-func (sb *SyslogBackend) SetFormatter(f *Formatter) {
+// SetFormatter defines the formatter for this backend.
+func (sb *SyslogBackend) SetFormatter(f Formatter) {
 	sb.formatter = f
 }
 
-// SetLevel changes the log level of the backend
+// SetLevel changes the log level of the backend.
 func (sb *SyslogBackend) SetLevel(level Level) {
 	sb.level = level
 }
 
-// Level returns the log level set for this backend
+// Level returns the log level set for this backend.
 func (sb *SyslogBackend) Level() Level {
 	return sb.level
 }
 
-// Reopen is a no-op
-func (sb *SyslogBackend) Reopen() error {
+// Reopen is a no-op.
+func (*SyslogBackend) Reopen() error {
 	return nil
 }
 
-// Close closes the connection to the syslog daemon
+// Close closes the connection to the syslog daemon.
 func (sb *SyslogBackend) Close() error {
-	return sb.w.Close()
+	if err := sb.w.Close(); err != nil {
+		return fmt.Errorf("cannot close syslog: %w", err)
+	}
+
+	return nil
 }
 
+//nolint:gochecknoglobals // global var is used by design
 var facilities = map[string]syslog.Priority{
 	"kern":     syslog.LOG_KERN,
 	"user":     syslog.LOG_USER,
@@ -109,7 +125,7 @@ var facilities = map[string]syslog.Priority{
 func facility(name string) (syslog.Priority, error) {
 	p, ok := facilities[strings.ToLower(name)]
 	if !ok {
-		return 0, fmt.Errorf("Facility '%s' does not exist", name)
+		return 0, fmt.Errorf("facility '%s' does not exist: %w", name, errUnknownFacility)
 	}
 
 	return p, nil

logger.go

@@ -7,37 +7,39 @@ import (
 	"sync"
 )
 
+const exitCodeFatal = 100
+
 // Logger is a facility that writes logs to one or more backands (files,
 // stdout/stderr, syslog, etc.) which can be configured independently
 //
 // Loggers are concurrent-safe.
 type Logger struct {
-	sync.Mutex
-
+	mutex    sync.Mutex
 	name     string
 	backends []Backend
 }
 
 // NewLogger initializes a new Logger with no backend and with the default log level.
-func NewLogger(name string) (l *Logger) {
-	l = &Logger{
+func NewLogger(name string) *Logger {
+	l := &Logger{
 		name: name,
 	}
-	return
+
+	return l
 }
 
 // AddBackend add a new Backend to the logger. All set backends are kept.
 func (l *Logger) AddBackend(b Backend) {
-	l.Lock()
-	defer l.Unlock()
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
 
 	l.backends = append(l.backends, b)
 }
 
 // SetBackend sets the backend list to the logger. Any existing backend will be lost.
 func (l *Logger) SetBackend(b ...Backend) {
-	l.Lock()
-	defer l.Unlock()
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
 
 	l.backends = b
 }
@@ -50,11 +52,11 @@ func (l *Logger) SetLevel(level Level) {
 }
 
 type buffer struct {
-	level  Level
 	logger *Logger
+	level  Level
 }
 
-func (b *buffer) Write(p []byte) (n int, err error) {
+func (b *buffer) Write(p []byte) (int, error) {
 	b.logger.Log(b.level, string(p))
 	return len(p), nil
 }
@@ -70,82 +72,86 @@ func (l *Logger) AsStdLog(level Level) *log.Logger {
 }
 
 // Log sends a record containing the message `m` to the registered backends
-// whose level is at least `level`
+// whose level is at least `level`.
 func (l *Logger) Log(level Level, m string) {
-	l.Lock()
-	defer l.Unlock()
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
 
 	r := NewRecord(l.name, level, m)
 	for _, backend := range l.backends {
 		if r.Level >= backend.Level() {
-			_ = backend.Write(r)
+			if err := backend.Write(r); err != nil {
+				//revive:disable-next-line:unhandled-error stop error handling recursion!
+				fmt.Fprintf(os.Stderr, "Cannot write logs: %v", err)
+			}
 		}
 	}
 }
 
-// Debug logs a message with the Debug level
+// Debug logs a message with the Debug level.
 func (l *Logger) Debug(text string) {
 	l.Log(Debug, text)
 }
 
 // Debugf formats the message with given args and logs the result with the
-// Debug level
+// Debug level.
 func (l *Logger) Debugf(text string, args ...interface{}) {
 	l.Debug(fmt.Sprintf(text, args...))
 }
 
-// Info logs a message with the Info level
+// Info logs a message with the Info level.
 func (l *Logger) Info(text string) {
 	l.Log(Info, text)
 }
 
 // Infof formats the message with given args and logs the result with the
-// Info level
+// Info level.
 func (l *Logger) Infof(text string, args ...interface{}) {
 	l.Info(fmt.Sprintf(text, args...))
 }
 
-// Warning logs a message with the Warning level
+// Warning logs a message with the Warning level.
 func (l *Logger) Warning(text string) {
 	l.Log(Warning, text)
 }
 
 // Warningf formats the message with given args and logs the result with the
-// Warning level
+// Warning level.
 func (l *Logger) Warningf(text string, args ...interface{}) {
 	l.Warning(fmt.Sprintf(text, args...))
 }
 
-// Error logs a message with the Error level
+// Error logs a message with the Error level.
 func (l *Logger) Error(text string) {
 	l.Log(Error, text)
 }
 
 // Errorf formats the message with given args and logs the result with the
-// Error level
+// Error level.
 func (l *Logger) Errorf(text string, args ...interface{}) {
 	l.Error(fmt.Sprintf(text, args...))
 }
 
-// Critical logs a message with the Critical level
+// Critical logs a message with the Critical level.
 func (l *Logger) Critical(text string) {
 	l.Log(Critical, text)
 }
 
-// Criticalf formats the message with given args and logs the result with the
-// Critical level
+// Criticalf formats the message with given args and logs the result with the.
+// Critical level.
 func (l *Logger) Criticalf(text string, args ...interface{}) {
 	l.Critical(fmt.Sprintf(text, args...))
 }
 
-// Fatal logs a message with the Fatal level
+// Fatal logs a message with the Fatal level.
 func (l *Logger) Fatal(text string) {
 	l.Log(Debug, text)
-	os.Exit(100)
+
+	os.Exit(exitCodeFatal) //nolint:revive // This is wanted if fatal is called
 }
 
 // Fatalf formats the message with given args and logs the result with the
-// Fatal level
+// Fatal level.
 func (l *Logger) Fatalf(text string, args ...interface{}) {
 	l.Fatal(fmt.Sprintf(text, args...))
 }

logging.go

@@ -12,27 +12,31 @@ package logging defines the following builtin backends:
 
 A backend can safely be used by multiple loggers.
 
-It is the caller's responsability to call Close on backends when they are not
+It is the caller's responsibility to call Close on backends when they are not
 used anymore to free their resources.
 
 */
 package logging
 
 import (
+	"errors"
 	"fmt"
 	"strings"
 	"sync"
 )
 
+//nolint:gochecknoglobals // designed this way
 var (
 	loggers map[string]*Logger
 	lock    sync.Mutex
+
+	errInvalidLogLevel = errors.New("invalid log level")
 )
 
-// Level is the type of log levels
+// Level is the type of log levels.
 type Level byte
 
-//nolint: golint
+//revive:disable:exported
 const (
 	Debug Level = iota
 	Info
@@ -43,9 +47,12 @@ const (
 	DefaultLevel = Info
 )
 
+//revive:enable:exported
+
+//nolint:gochecknoglobals // designed this way
 var levelNames = [6]string{"DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL", "FATAL"}
 
-// Name returns the name of the log level
+// Name returns the name of the log level.
 func (l Level) Name() string {
 	return levelNames[l]
 }
@@ -58,7 +65,8 @@ func LevelByName(l string) (Level, error) {
 			return Level(pos), nil
 		}
 	}
-	return Debug, fmt.Errorf("Invalid log level %s", l)
+
+	return Debug, fmt.Errorf("unknown log level %q: %w", l, errInvalidLogLevel)
 }
 
 // Formatter is the types of the functions that can be used to format a log
@@ -66,14 +74,15 @@ func LevelByName(l string) (Level, error) {
 type Formatter func(*Record) string
 
 // GetLogger returns a logger given its name. if the logger does not exist, it
-// initializes one with the defaults (it logs to stdout with level debug)
-func GetLogger(name string) (l *Logger) {
+// initializes one with the defaults (it logs to stdout with level INFO).
+func GetLogger(name string) *Logger {
 	lock.Lock()
 	defer lock.Unlock()
 
 	if name == "" {
 		name = "default"
 	}
+
 	l, ok := loggers[name]
 	if !ok {
 		l = NewLogger(name)
@@ -82,21 +91,23 @@ func GetLogger(name string) (l *Logger) {
 		l.SetLevel(DefaultLevel)
 		loggers[name] = l
 	}
+
 	return l
 }
 
-var defaultFormatter Formatter = func(r *Record) string {
+func defaultFormatter(r *Record) string {
 	return fmt.Sprintf("%s [%-8s] %s: %s\n",
 		r.Timestamp.Format("2006/01/02 15:04:05"), r.Level.Name(), r.Logger,
 		strings.TrimSpace(r.Message))
 }
 
-var basicFormatter Formatter = func(r *Record) string {
+func basicFormatter(r *Record) string {
 	return fmt.Sprintf("%s: %s", r.Logger, strings.TrimSpace(r.Message))
 }
 
+//nolint:gochecknoinits // init is used by design
 func init() {
-	loggers = make(map[string]*Logger, 3)
+	loggers = map[string]*Logger{}
 
 	logger := NewLogger("default")
 	backend := NewStdoutBackend()

logging_test.go

@@ -3,11 +3,14 @@ package logging
 import "testing"
 
 func Test_LevelByName(t *testing.T) {
+	t.Parallel()
+
 	for _, levelName := range levelNames {
 		l, e := LevelByName(levelName)
 		if e != nil {
 			t.Errorf("level %s not recognized", levelName)
 		}
+
 		if l.Name() != levelName {
 			t.Errorf("expected '%s', got '%s'", levelName, l.Name())
 		}

record.go

@@ -5,7 +5,7 @@ import (
 )
 
 // Record contains the data to be logged. It is passed to a formatter to
-// generate the logged message
+// generate the logged message.
 type Record struct {
 	Logger    string
 	Timestamp time.Time
@@ -13,13 +13,12 @@ type Record struct {
 	Message   string
 }
 
-// NewRecord creates a new record, setting its timestamp to time.Now()
-func NewRecord(name string, l Level, m string) (r *Record) {
-	r = &Record{
+// NewRecord creates a new record, setting its timestamp to time.Now().
+func NewRecord(name string, l Level, m string) *Record {
+	return &Record{
 		Logger:    name,
 		Level:     l,
 		Message:   m,
 		Timestamp: time.Now(),
 	}
-	return
 }