zapslog: inline group if empty key uber-go#1402

Signed-off-by: junya koyama <arukiidou@yahoo.co.jp>

exp/zapslog/handler.go

@@ -88,6 +88,10 @@ func convertAttrToField(attr slog.Attr) zapcore.Field {
 	case slog.KindUint64:
 		return zap.Uint64(attr.Key, attr.Value.Uint64())
 	case slog.KindGroup:
+		if attr.Key == "" {
+			// Inlines recursively.
+			return zap.Inline(groupObject(attr.Value.Group()))
+		}
 		return zap.Object(attr.Key, groupObject(attr.Value.Group()))
 	case slog.KindLogValuer:
 		return convertAttrToField(slog.Attr{

exp/zapslog/handler_test.go

@@ -150,6 +150,39 @@ func TestWithName(t *testing.T) {
 	})
 }
 
+func TestInlineGroup(t *testing.T) {
+	t.Parallel()
+	fac, observedLogs := observer.New(zapcore.DebugLevel)
+	t.Run("inline-group", func(t *testing.T) {
+		sl := slog.New(NewHandler(fac))
+		sl.Info("msg", "a", "b", slog.Group("", slog.String("c", "d")), "e", "f")
+
+		logs := observedLogs.TakeAll()
+		require.Len(t, logs, 1, "Expected exactly one entry to be logged")
+		entry := logs[0]
+		assert.Equal(t, "", entry.LoggerName, "Unexpected logger name")
+		assert.Equal(t, map[string]any{
+			"a": "b",
+			"c": "d",
+			"e": "f",
+		}, logs[0].ContextMap(), "Unexpected context")
+	})
+	t.Run("inline-group-recursive", func(t *testing.T) {
+		sl := slog.New(NewHandler(fac))
+		sl.Info("msg", "a", "b", slog.Group("", slog.Group("", slog.Group("", slog.String("c", "d"))), slog.Group("", "e", "f")))
+
+		logs := observedLogs.TakeAll()
+		require.Len(t, logs, 1, "Expected exactly one entry to be logged")
+		entry := logs[0]
+		assert.Equal(t, "", entry.LoggerName, "Unexpected logger name")
+		assert.Equal(t, map[string]any{
+			"a": "b",
+			"c": "d",
+			"e": "f",
+		}, logs[0].ContextMap(), "Unexpected context")
+	})
+}
+
 type Token string
 
 func (Token) LogValue() slog.Value {