fix: inherit log level changes in wrapped subloggers

logger.go

@@ -30,6 +30,8 @@ type Logger struct {
 	isDiscard uint32
 
 	level           int64
+	hasCustomLevel  uint32
+	parent          *Logger
 	prefix          string
 	timeFunc        TimeFunction
 	timeFormat      string
@@ -58,7 +60,7 @@ func (l *Logger) Log(level Level, msg any, keyvals ...any) {
 	}
 
 	// check if the level is allowed
-	if atomic.LoadInt64(&l.level) > int64(level) {
+	if l.getLevel() > int64(level) {
 		return
 	}
 
@@ -231,18 +233,28 @@ func (l *Logger) SetReportCaller(report bool) {
 	l.reportCaller = report
 }
 
+func (l *Logger) getLevel() int64 {
+	for cur := l; cur != nil; cur = cur.parent {
+		if atomic.LoadUint32(&cur.hasCustomLevel) != 0 || cur.parent == nil {
+			return atomic.LoadInt64(&cur.level)
+		}
+	}
+	return int64(InfoLevel)
+}
+
 // GetLevel returns the current level.
 func (l *Logger) GetLevel() Level {
 	l.mu.RLock()
 	defer l.mu.RUnlock()
-	return Level(l.level)
+	return Level(l.getLevel())
 }
 
 // SetLevel sets the current level.
 func (l *Logger) SetLevel(level Level) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
 	atomic.StoreInt64(&l.level, int64(level))
+	atomic.StoreUint32(&l.hasCustomLevel, 1)
 }
 
 // GetPrefix returns the current prefix.
@@ -340,6 +352,8 @@ func (l *Logger) With(keyvals ...any) *Logger {
 	sl.fields = append(make([]any, 0, len(l.fields)+len(keyvals)), l.fields...)
 	sl.fields = append(sl.fields, keyvals...)
 	sl.styles = &st
+	sl.parent = l
+	sl.hasCustomLevel = 0
 	return &sl
 }
 

logger_121.go

@@ -6,7 +6,6 @@ import (
 	"context"
 	"log/slog"
 	"runtime"
-	"sync/atomic"
 )
 
 // type aliases for slog.
@@ -24,7 +23,7 @@ const slogKindGroup = slog.KindGroup
 //
 // Implements slog.Handler.
 func (l *Logger) Enabled(_ context.Context, level slog.Level) bool {
-	return atomic.LoadInt64(&l.level) <= int64(level)
+	return l.getLevel() <= int64(level)
 }
 
 // Handle handles the Record. It will only be called if Enabled returns true.

logger_no121.go

@@ -5,7 +5,6 @@ package log
 import (
 	"context"
 	"runtime"
-	"sync/atomic"
 
 	"golang.org/x/exp/slog"
 )
@@ -25,7 +24,7 @@ const slogKindGroup = slog.KindGroup
 //
 // Implements slog.Handler.
 func (l *Logger) Enabled(_ context.Context, level slog.Level) bool {
-	return atomic.LoadInt64(&l.level) <= int64(level)
+	return l.getLevel() <= int64(level)
 }
 
 // Handle handles the Record. It will only be called if Enabled returns true.

logger_test.go

@@ -287,3 +287,159 @@ func TestCustomLevel(t *testing.T) {
 	l.Logf(level500, "foo")
 	assert.Equal(t, "foo\n", buf.String())
 }
+
+func TestWrappedLoggerInheritsLevel(t *testing.T) {
+	var buf bytes.Buffer
+	logger := NewWithOptions(&buf, Options{
+		Level:           InfoLevel,
+		ReportTimestamp: false,
+		ReportCaller:    false,
+	})
+
+	wrappedLogger := logger.With("component", "auth")
+
+	// Initially InfoLevel: debug message must be suppressed on child.
+	wrappedLogger.Debug("auth debug suppressed")
+	assert.Empty(t, buf.String())
+
+	// Changing parent level to DebugLevel must propagate to child.
+	logger.SetLevel(DebugLevel)
+	assert.Equal(t, DebugLevel, wrappedLogger.GetLevel())
+
+	wrappedLogger.Debug("auth debug allowed")
+	assert.Equal(t, "DEBUG auth debug allowed component=auth\n", buf.String())
+
+	// Changing parent level to WarnLevel must suppress info messages on child.
+	buf.Reset()
+	logger.SetLevel(WarnLevel)
+	assert.Equal(t, WarnLevel, wrappedLogger.GetLevel())
+
+	wrappedLogger.Info("auth info suppressed")
+	assert.Empty(t, buf.String())
+
+	wrappedLogger.Warn("auth warning allowed")
+	assert.Equal(t, "WARN  auth warning allowed component=auth\n", buf.String())
+}
+
+func TestWrappedLoggerExplicitChildLevel(t *testing.T) {
+	var buf bytes.Buffer
+	logger := NewWithOptions(&buf, Options{
+		Level:           InfoLevel,
+		ReportTimestamp: false,
+		ReportCaller:    false,
+	})
+
+	child := logger.With("component", "worker")
+	child.SetLevel(WarnLevel)
+
+	// Child override must not mutate parent level.
+	assert.Equal(t, InfoLevel, logger.GetLevel())
+	assert.Equal(t, WarnLevel, child.GetLevel())
+
+	// Subsequent parent level change must not override explicit child setting.
+	logger.SetLevel(DebugLevel)
+	assert.Equal(t, DebugLevel, logger.GetLevel())
+	assert.Equal(t, WarnLevel, child.GetLevel())
+
+	// Parent permits debug messages while child suppresses them.
+	logger.Debug("parent debug allowed")
+	assert.Equal(t, "DEBUG parent debug allowed\n", buf.String())
+
+	buf.Reset()
+	child.Debug("child debug suppressed")
+	assert.Empty(t, buf.String())
+
+	child.Info("child info suppressed")
+	assert.Empty(t, buf.String())
+
+	child.Warn("child warn allowed")
+	assert.Equal(t, "WARN  child warn allowed component=worker\n", buf.String())
+}
+
+func TestWrappedLoggerHierarchy(t *testing.T) {
+	var buf bytes.Buffer
+	root := NewWithOptions(&buf, Options{
+		Level:           InfoLevel,
+		ReportTimestamp: false,
+		ReportCaller:    false,
+	})
+
+	child := root.With("tier", 1)
+	grandchild := child.With("tier", 2)
+
+	assert.Equal(t, InfoLevel, root.GetLevel())
+	assert.Equal(t, InfoLevel, child.GetLevel())
+	assert.Equal(t, InfoLevel, grandchild.GetLevel())
+
+	// Root update propagates down entire hierarchy.
+	root.SetLevel(DebugLevel)
+	assert.Equal(t, DebugLevel, root.GetLevel())
+	assert.Equal(t, DebugLevel, child.GetLevel())
+	assert.Equal(t, DebugLevel, grandchild.GetLevel())
+
+	grandchild.Debug("grandchild debug")
+	assert.Equal(t, "DEBUG grandchild debug tier=1 tier=2\n", buf.String())
+
+	// Overriding child propagates to grandchild, while root is unaffected.
+	buf.Reset()
+	child.SetLevel(ErrorLevel)
+	assert.Equal(t, DebugLevel, root.GetLevel())
+	assert.Equal(t, ErrorLevel, child.GetLevel())
+	assert.Equal(t, ErrorLevel, grandchild.GetLevel())
+
+	grandchild.Warn("grandchild warn suppressed")
+	assert.Empty(t, buf.String())
+
+	grandchild.Error("grandchild error allowed")
+	assert.Equal(t, "ERROR grandchild error allowed tier=1 tier=2\n", buf.String())
+
+	buf.Reset()
+	root.Debug("root debug allowed")
+	assert.Equal(t, "DEBUG root debug allowed\n", buf.String())
+}
+
+func TestWrappedLoggerRace(t *testing.T) {
+	w := io.Discard
+	logger := New(w)
+	child := logger.With("component", "worker")
+	grandchild := child.With("task", 42)
+
+	var wg sync.WaitGroup
+	levels := []Level{DebugLevel, InfoLevel, WarnLevel, ErrorLevel}
+
+	for i := 0; i < 20; i++ {
+		wg.Add(4)
+		lvl := levels[i%len(levels)]
+
+		go func() {
+			defer wg.Done()
+			logger.SetLevel(lvl)
+			logger.Debug("logger debug")
+			logger.Info("logger info")
+		}()
+
+		go func() {
+			defer wg.Done()
+			child.GetLevel()
+			child.Info("child info")
+			child.Warn("child warn")
+		}()
+
+		go func() {
+			defer wg.Done()
+			grandchild.GetLevel()
+			grandchild.Debug("grandchild debug")
+			grandchild.Error("grandchild error")
+		}()
+
+		go func(idx int) {
+			defer wg.Done()
+			if idx%2 == 0 {
+				child.SetLevel(lvl)
+			}
+		}(i)
+	}
+
+	wg.Wait()
+}
+

pkg.go

@@ -50,6 +50,7 @@ func NewWithOptions(w io.Writer, o Options) *Logger {
 		mu:              &sync.RWMutex{},
 		helpers:         &sync.Map{},
 		level:           int64(o.Level),
+		hasCustomLevel:  1,
 		reportTimestamp: o.ReportTimestamp,
 		reportCaller:    o.ReportCaller,
 		prefix:          o.Prefix,