Reject buffered writes after BufferedWriteSyncer.Stop

zapcore/buffered_write_syncer.go

@@ -22,6 +22,7 @@ package zapcore
 
 import (
 	"bufio"
+	"io"
 	"sync"
 	"time"
 
@@ -134,10 +135,15 @@ func (s *BufferedWriteSyncer) initialize() {
 
 // Write writes log data into buffer syncer directly, multiple Write calls will be batched,
 // and log data will be flushed to disk when the buffer is full or periodically.
+// Write returns io.ErrClosedPipe after Stop has been called.
 func (s *BufferedWriteSyncer) Write(bs []byte) (int, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
+	if s.stopped {
+		return 0, io.ErrClosedPipe
+	}
+
 	if !s.initialized {
 		s.initialize()
 	}
@@ -193,14 +199,14 @@ func (s *BufferedWriteSyncer) Stop() (err error) {
 		s.mu.Lock()
 		defer s.mu.Unlock()
 
-		if !s.initialized {
+		if s.stopped {
 			return false
 		}
+		s.stopped = true
 
-		if s.stopped {
+		if !s.initialized {
 			return false
 		}
-		s.stopped = true
 
 		s.ticker.Stop()
 		close(s.stop) // tell flushLoop to stop

zapcore/buffered_write_syncer_test.go

@@ -22,6 +22,7 @@ package zapcore
 
 import (
 	"bytes"
+	"io"
 	"testing"
 	"time"
 
@@ -146,3 +147,30 @@ func TestBufferWriterWithoutStart(t *testing.T) {
 		assert.NoError(t, ws.Sync(), "Sync must not fail")
 	})
 }
+
+func TestBufferedWriteSyncerWriteAfterStop(t *testing.T) {
+	for _, initialized := range []bool{false, true} {
+		name := "before first write"
+		if initialized {
+			name = "after first write"
+		}
+		t.Run(name, func(t *testing.T) {
+			buf := &bytes.Buffer{}
+			ws := &BufferedWriteSyncer{WS: AddSync(buf)}
+			t.Cleanup(func() { assert.NoError(t, ws.Stop()) })
+			if initialized {
+				requireWriteWorks(t, ws)
+			}
+			require.NoError(t, ws.Stop())
+			before := buf.String()
+			for attempt := 0; attempt < 2; attempt++ {
+				n, err := ws.Write([]byte("lost log"))
+				assert.Zero(t, n)
+				assert.ErrorIs(t, err, io.ErrClosedPipe)
+				require.NoError(t, ws.Stop())
+			}
+			require.NoError(t, ws.Sync())
+			assert.Equal(t, before, buf.String())
+		})
+	}
+}