修改为0的判断

services/wallet-service/internal/service/wallet/service_test.go

@@ -382,6 +382,55 @@ func TestDebitGiftUsesRegionalReturnCoinRatioWithoutChangingHostDiamonds(t *test
 	}
 }
 
+func TestDebitGiftAllowsZeroReturnCoinRatio(t *testing.T) {
+	repository := mysqltest.NewRepository(t)
+	svc := walletservice.New(repository)
+	cases := []struct {
+		name     string
+		giftID   string
+		giftType string
+		regionID int64
+		senderID int64
+		targetID int64
+		wantHeat int64
+	}{
+		{name: "lucky", giftID: "zero-return-lucky-gift", giftType: resourcedomain.GiftTypeLucky, regionID: 7702, senderID: 14601, targetID: 14602, wantHeat: 10},
+		{name: "super-lucky", giftID: "zero-return-super-lucky-gift", giftType: resourcedomain.GiftTypeSuperLucky, regionID: 7703, senderID: 14603, targetID: 14604, wantHeat: 1},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			repository.SetBalance(tc.senderID, 500)
+			repository.SetGiftPrice(tc.giftID, "v1", 100, 100, 100)
+			repository.SetGiftType(tc.giftID, tc.giftType)
+			// 0% 返币是后台可配置的合法业务结果；扣费和房间贡献仍要按礼物真实价格结算。
+			repository.SetGiftReturnCoinRatio(tc.regionID, tc.giftType, "0.00")
+
+			receipt, err := svc.DebitGift(context.Background(), ledger.DebitGiftCommand{
+				CommandID:      "cmd-zero-return-" + tc.name,
+				RoomID:         "room-zero-return-" + tc.name,
+				SenderUserID:   tc.senderID,
+				SenderRegionID: 1001,
+				RegionID:       tc.regionID,
+				TargetUserID:   tc.targetID,
+				GiftID:         tc.giftID,
+				GiftCount:      1,
+				PriceVersion:   "v1",
+			})
+			if err != nil {
+				t.Fatalf("DebitGift with zero return ratio failed: %v", err)
+			}
+			if receipt.CoinSpent != 100 || receipt.HeatValue != tc.wantHeat || receipt.BalanceAfter != 400 {
+				t.Fatalf("zero return ratio settlement mismatch: %+v want heat %d", receipt, tc.wantHeat)
+			}
+			assertBalance(t, svc, tc.senderID, ledger.AssetCoin, 400)
+			assertBalance(t, svc, tc.targetID, ledger.AssetCoin, 0)
+			if got := repository.CountRows("wallet_outbox", "transaction_id = ? AND event_type = ?", receipt.TransactionID, "WalletGiftIncomeCredited"); got != 0 {
+				t.Fatalf("zero return ratio must not publish gift income event, got %d", got)
+			}
+		})
+	}
+}
+
 func TestBatchDebitGiftAppliesGlobalDefaultGiftDiamondRatioToEachTargetHeatValue(t *testing.T) {
 	repository := mysqltest.NewRepository(t)
 	repository.SetBalance(15001, 1000)

services/wallet-service/internal/storage/mysql/gift_pricing.go

@@ -174,6 +174,10 @@ func giftDiamondAmount(chargeAmount int64, ratioPPM int64) (int64, error) {
 	if chargeAmount < 0 || ratioPPM < 0 {
 		return 0, xerr.New(xerr.InvalidArgument, "gift diamond amount is invalid")
 	}
+	if chargeAmount == 0 || ratioPPM == 0 {
+		// 0 金额或 0% 比例都是合法业务结果；这里只跳过乘法溢出工具的正数乘数约束，不放宽负数和数量校验。
+		return 0, nil
+	}
 	product, err := checkedMul(chargeAmount, ratioPPM)
 	if err != nil {
 		return 0, err