Fix race condition in WithLazy implementation (#1426)

zapcore/lazy_with.go

@@ -23,7 +23,7 @@ package zapcore
 import "sync"
 
 type lazyWithCore struct {
-	Core
+	core   Core
 	sync.Once
 	fields []Field
 }
@@ -32,23 +32,38 @@ type lazyWithCore struct {
 // the logger is written to (or is further chained in a lon-lazy manner).
 func NewLazyWith(core Core, fields []Field) Core {
 	return &lazyWithCore{
-		Core:   core,
+		core:   core,
 		fields: fields,
 	}
 }
 
 func (d *lazyWithCore) initOnce() {
 	d.Once.Do(func() {
-		d.Core = d.Core.With(d.fields)
+		d.core = d.core.With(d.fields)
 	})
 }
 
 func (d *lazyWithCore) With(fields []Field) Core {
 	d.initOnce()
-	return d.Core.With(fields)
+	return d.core.With(fields)
 }
 
 func (d *lazyWithCore) Check(e Entry, ce *CheckedEntry) *CheckedEntry {
 	d.initOnce()
-	return d.Core.Check(e, ce)
+	return d.core.Check(e, ce)
+}
+
+func (d *lazyWithCore) Enabled(level Level) bool {
+	d.initOnce()
+	return d.core.Enabled(level)
+}
+
+func (d *lazyWithCore) Write(e Entry, fields []Field) error {
+	d.initOnce()
+	return d.core.Write(e, fields)
+}
+
+func (d *lazyWithCore) Sync() error {
+	d.initOnce()
+	return d.core.Sync()
 }

zapcore/lazy_with_test.go

@@ -21,6 +21,7 @@
 package zapcore_test
 
 import (
+	"sync"
 	"sync/atomic"
 	"testing"
 
@@ -152,3 +153,34 @@ func TestLazyCore(t *testing.T) {
 		})
 	}
 }
+
+// TestLazyCoreRace tests concurrent access to lazyWithCore methods
+// This is a regression test for issue #1426
+func TestLazyCoreRace(t *testing.T) {
+	core, _ := observer.New(zapcore.InfoLevel)
+	lazyCore := zapcore.NewLazyWith(core, []zapcore.Field{
+		makeInt64Field("lazy", 42),
+	})
+
+	var wg sync.WaitGroup
+	const numGoroutines = 50
+
+	// Test concurrent access to Enabled() method which was the source of the race
+	for i := 0; i < numGoroutines; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+
+			// These operations should not race
+			_ = lazyCore.Enabled(zapcore.InfoLevel)
+			_ = lazyCore.Enabled(zapcore.DebugLevel)
+
+			// Also test other methods for good measure
+			if ce := lazyCore.Check(zapcore.Entry{Level: zapcore.InfoLevel, Message: "test"}, nil); ce != nil {
+				_ = lazyCore.Write(zapcore.Entry{Level: zapcore.InfoLevel, Message: "test"}, nil)
+			}
+		}()
+	}
+
+	wg.Wait()
+}