logger/slog: fix dedup keys

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

logger/options.go

@@ -106,7 +106,9 @@ func WithAddFields(fields ...interface{}) Option {
 					}
 				}
 			}
-			o.Fields = append(o.Fields, fields...)
+			if len(fields) > 0 {
+				o.Fields = append(o.Fields, fields...)
+			}
 		} else {
 			o.Fields = append(o.Fields, fields...)
 		}

logger/slog/slog.go

@@ -142,6 +142,7 @@ func (s *slogLogger) Fields(fields ...interface{}) logger.Logger {
 	s.mu.RUnlock()
 
 	l := &slogLogger{opts: options}
+	logger.WithAddFields(fields...)(&l.opts)
 
 	if len(options.ContextAttrFuncs) == 0 {
 		options.ContextAttrFuncs = logger.DefaultContextAttrFuncs

logger/slog/slog_test.go

@@ -15,7 +15,29 @@ import (
 	"go.unistack.org/micro/v3/metadata"
 )
 
-func TestWithDuplicate(t *testing.T) {
+func TestWithFields(t *testing.T) {
+	ctx := context.TODO()
+	buf := bytes.NewBuffer(nil)
+	l := NewLogger(logger.WithLevel(logger.InfoLevel), logger.WithOutput(buf),
+		WithHandlerFunc(slog.NewTextHandler),
+		logger.WithDedupKeys(true),
+	)
+	if err := l.Init(logger.WithFields("key1", "val1")); err != nil {
+		t.Fatal(err)
+	}
+
+	l.Info(ctx, "msg1")
+
+	l = l.Fields("key1", "val2")
+
+	l.Info(ctx, "msg2")
+
+	if !bytes.Contains(buf.Bytes(), []byte(`msg=msg2 key1=val1`)) {
+		t.Fatalf("logger error not works, buf contains: %s", buf.Bytes())
+	}
+}
+
+func TestWithDedupKeysWithAddFields(t *testing.T) {
 	ctx := context.TODO()
 	buf := bytes.NewBuffer(nil)
 	l := NewLogger(logger.WithLevel(logger.InfoLevel), logger.WithOutput(buf),