use custom labels for front attributes

handler.go

@@ -39,6 +39,17 @@ func (h namedHandler) Handle(ctx context.Context, record slog.Record) error {
 	opts := &slog.HandlerOptions{
 		AddSource: config.EnableSource,
 		Level:     leveler,
+		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+			switch a.Key {
+			case slog.MessageKey, slog.LevelKey, slog.TimeKey:
+				// ignore these built in attributes
+				// so that we can customize the order
+				return slog.Attr{}
+			case slog.SourceKey:
+				a.Key = "$source"
+			}
+			return a
+		},
 	}
 
 	var output io.Writer

logger.go

@@ -88,12 +88,17 @@ func (l *Logger) log(ctx context.Context, level slog.Level, err error, msg strin
 	}
 
 	r := slog.NewRecord(time.Now(), level, msg, pcs[0])
-	r.Add(slog.Any("name", l.name))
+	// add front attributes in specific order
+	r.Add(slog.String("$time", r.Time.Format(time.DateTime)))
+	r.Add(slog.String("$name", l.name))
+	r.Add(slog.Any("$level", r.Level))
+	r.Add(slog.String("$msg", r.Message))
+	// add remaining attributes
 	r.AddAttrs(args...)
 
 	// add stack trace if enabled
 	if err != nil && config.EnableStackTrace {
-		r.Add("stacktrace", fmt.Sprintf("%+v", err))
+		r.Add("$stack", fmt.Sprintf("%+v", err))
 	}
 
 	_ = l.handler.Handle(ctx, r)

logger_test.go

@@ -49,9 +49,11 @@ func TestLoggerLogWithConfigOverride(t *testing.T) {
 	assert.Equal(t, "test", handler.records[0].Message)
 
 	attrs := []slog.Attr{
-		slog.Any("name", "test"),
+		slog.Any("$name", "test"),
+		slog.Any("$level", slog.LevelInfo),
+		slog.Any("$msg", "test"),
 		slog.Any("arg1", "val1"),
-		slog.Any("stacktrace", fmt.Sprintf("%+v", err)),
+		slog.Any("$stack", fmt.Sprintf("%+v", err)),
 	}
 	assertRecordAttrs(t, handler.records[0], attrs...)
 }
@@ -71,7 +73,14 @@ func TestLoggerInfoWithEnableSource(t *testing.T) {
 	assert.Equal(t, slog.LevelInfo, handler.records[0].Level)
 	assert.Equal(t, "test", handler.records[0].Message)
 	assert.NotEqual(t, uintptr(0x00), handler.records[0].PC)
-	assertRecordAttrs(t, handler.records[0], slog.Any("name", "test"), slog.Any("arg1", "val1"))
+
+	attrs := []slog.Attr{
+		slog.Any("$name", "test"),
+		slog.Any("$level", slog.LevelInfo),
+		slog.Any("$msg", "test"),
+		slog.Any("arg1", "val1"),
+	}
+	assertRecordAttrs(t, handler.records[0], attrs...)
 }
 
 func TestLoggerWithAttrs(t *testing.T) {
@@ -109,7 +118,9 @@ func assertRecordAttrs(
 ) {
 	var actual []slog.Attr
 	record.Attrs(func(a slog.Attr) bool {
-		actual = append(actual, a)
+		if a.Key != "$time" {
+			actual = append(actual, a)
+		}
 		return true
 	})
 	assert.Equal(t, expected, actual)