fix(backend): 商品编码改用最大序号生成不复用软删号 + 加 (shop_id,code) 唯一约束，根治重复编码

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YZ4DskSRKsSiheQonFtQvx

CHANGELOG-server.md

@@ -5,6 +5,11 @@
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.0.68] - 2026-06-21
+
+### 修复
+- 根治商品编码可能重复的问题：自动编码改为按现有最大序号递增生成（不再复用已删除商品占用过的编号、并发下也不会撞号），并在数据库层为「同门店 + 编码」加唯一约束，从此重复编码无法静默产生
+
 ## [1.0.67] - 2026-06-20
 
 ### 修复

backend/internal/handler/product.go

@@ -62,6 +62,29 @@ func (h *ProductHandler) List(c *gin.Context) {
 	})
 }
 
+// nextProductCode 生成该门店下一个自动商品编码（P001、P002…）。
+// 取现有 P 开头编码的最大数字序号 +1，**含软删行**（deleted_at 非空也计入，不复用已删商品占用过的号）。
+// 不加行锁——并发下两请求可能算出同号，由 uk_shop_code 唯一约束 + 调用方 ErrDuplicatedKey 重试兜底。
+// 用 GORM 表达式（非 MySQL 方言 SQL），sqlite 单测也能跑。
+func nextProductCode(tx *gorm.DB, shopID uint64) (string, error) {
+	var codes []string
+	if err := tx.Model(&model.Product{}).
+		Where("shop_id = ? AND code LIKE 'P%'", shopID).
+		Pluck("code", &codes).Error; err != nil {
+		return "", err
+	}
+	maxN := 0
+	for _, c := range codes {
+		if len(c) < 2 {
+			continue
+		}
+		if n, err := strconv.Atoi(c[1:]); err == nil && n > maxN {
+			maxN = n
+		}
+	}
+	return fmt.Sprintf("P%03d", maxN+1), nil
+}
+
 // Create POST /api/v1/products
 func (h *ProductHandler) Create(c *gin.Context) {
 	shopID := middleware.GetShopID(c)
@@ -74,31 +97,24 @@ func (h *ProductHandler) Create(c *gin.Context) {
 	product.PublicID = uuid.New().String()
 	product.NamePinyin, product.NameInitials = util.ToPinyin(product.Name)
 
-	// Auto-generate product code if not provided (e.g. P001, P002)
-	// Retry up to 5 times on duplicate key to handle concurrent creates
-	if product.Code == "" {
-		var count int64
-		h.db.Model(&model.Product{}).
-			Where("shop_id = ? AND deleted_at IS NULL", shopID).
-			Count(&count)
-		product.Code = fmt.Sprintf("P%03d", count+1)
-	}
-
+	// 未显式指定编码时自动生成（事务内 max+1）；撞 uk_shop_code 唯一约束则重算下一号重试（应对并发）。
+	autoCode := product.Code == ""
 	var createErr error
 	for attempt := 0; attempt < 5; attempt++ {
-		if createErr = h.db.Create(&product).Error; createErr == nil {
+		createErr = h.db.Transaction(func(tx *gorm.DB) error {
+			if autoCode {
+				code, err := nextProductCode(tx, shopID)
+				if err != nil {
+					return err
+				}
+				product.Code = code
+			}
+			product.ID = 0
+			return tx.Create(&product).Error
+		})
+		if createErr == nil || !autoCode || !errors.Is(createErr, gorm.ErrDuplicatedKey) {
 			break
 		}
-		if !errors.Is(createErr, gorm.ErrDuplicatedKey) {
-			break
-		}
-		// Duplicate code: try next slot
-		var count int64
-		h.db.Model(&model.Product{}).
-			Where("shop_id = ? AND deleted_at IS NULL", shopID).
-			Count(&count)
-		product.ID = 0
-		product.Code = fmt.Sprintf("P%03d", count+int64(attempt)+2)
 	}
 	if createErr != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": createErr.Error()})
@@ -256,25 +272,37 @@ func (h *ProductHandler) FindOrCreate(c *gin.Context) {
 		return
 	}
 
-	var count int64
-	h.db.Model(&model.Product{}).Where("shop_id = ? AND deleted_at IS NULL", shopID).Count(&count)
 	namePinyin, nameInitials := util.ToPinyin(req.Name)
-	product = model.Product{
-		TenantBase:       model.TenantBase{ShopID: shopID},
-		PublicID:         uuid.New().String(),
-		Name:             req.Name,
-		Series:           req.Series,
-		Spec:             req.Spec,
-		Code:             fmt.Sprintf("P%03d", count+1),
-		NamePinyin:       namePinyin,
-		NameInitials:     nameInitials,
-		OriginID:         req.OriginID,
-		ShelfLifeID:      req.ShelfLifeID,
-		StorageID:        req.StorageID,
-		DescriptionDocID: req.DescriptionDocID,
+	// 事务内 max+1 生成编码；撞 uk_shop_code 唯一约束则重算下一号重试（应对并发）。
+	var createErr error
+	for attempt := 0; attempt < 5; attempt++ {
+		createErr = h.db.Transaction(func(tx *gorm.DB) error {
+			code, err := nextProductCode(tx, shopID)
+			if err != nil {
+				return err
+			}
+			product = model.Product{
+				TenantBase:       model.TenantBase{ShopID: shopID},
+				PublicID:         uuid.New().String(),
+				Name:             req.Name,
+				Series:           req.Series,
+				Spec:             req.Spec,
+				Code:             code,
+				NamePinyin:       namePinyin,
+				NameInitials:     nameInitials,
+				OriginID:         req.OriginID,
+				ShelfLifeID:      req.ShelfLifeID,
+				StorageID:        req.StorageID,
+				DescriptionDocID: req.DescriptionDocID,
+			}
+			return tx.Create(&product).Error
+		})
+		if createErr == nil || !errors.Is(createErr, gorm.ErrDuplicatedKey) {
+			break
+		}
 	}
-	if createErr := h.db.Create(&product).Error; createErr != nil {
-		// Race condition: try to find the record created by another request
+	if createErr != nil {
+		// Race condition: 并发可能已按同 name/series/spec 建好，回查返回既有
 		if h.db.Where("shop_id = ? AND name = ? AND series = ? AND spec = ? AND deleted_at IS NULL",
 			shopID, req.Name, req.Series, req.Spec).First(&product).Error == nil {
 			util.RespondSuccess(c, product)

backend/internal/handler/product_test.go

@@ -2,13 +2,16 @@ package handler
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"gorm.io/gorm"
 
+	"github.com/wangjia/jiu/backend/internal/model"
 	"github.com/wangjia/jiu/backend/testutil"
 )
 
@@ -199,3 +202,67 @@ func TestProductHandler_Create_ShopIDFromToken(t *testing.T) {
 	dataBytes, _ := json.Marshal(data)
 	_ = dataBytes
 }
+
+// 自动编码按最大序号递增：P001 → P002 → P003。
+func TestProductHandler_AutoCode_Increment(t *testing.T) {
+	db := testutil.SetupTestDB()
+	shop := testutil.CreateTestShop(db, "AC001")
+	user := testutil.CreateTestUser(db, shop.ID, "admin", "pass", "admin")
+	token := getAuthToken(user.ID, shop.ID, "admin")
+	r := setupProtectedRouter(db)
+
+	var codes []string
+	for i := 0; i < 3; i++ {
+		w := makeRequest(r, "POST", "/api/v1/products", token, map[string]interface{}{
+			"name": fmt.Sprintf("AutoP %d", i), "unit": "个",
+		})
+		require.Equal(t, http.StatusCreated, w.Code)
+		data := parseResponse(w)["data"].(map[string]interface{})
+		codes = append(codes, data["code"].(string))
+	}
+	assert.Equal(t, []string{"P001", "P002", "P003"}, codes)
+}
+
+// 软删商品后，新建不复用被删的号（旧 count+1 逻辑会复用 → 重复，此为根因修复回归测试）。
+func TestProductHandler_AutoCode_NoReuseAfterSoftDelete(t *testing.T) {
+	db := testutil.SetupTestDB()
+	shop := testutil.CreateTestShop(db, "AC002")
+	user := testutil.CreateTestUser(db, shop.ID, "admin", "pass", "admin")
+	token := getAuthToken(user.ID, shop.ID, "admin")
+	r := setupProtectedRouter(db)
+
+	var lastID uint64
+	for i := 0; i < 3; i++ { // P001 P002 P003
+		w := makeRequest(r, "POST", "/api/v1/products", token, map[string]interface{}{
+			"name": fmt.Sprintf("NR %d", i), "unit": "个",
+		})
+		require.Equal(t, http.StatusCreated, w.Code)
+		lastID = extractID(w)
+	}
+	// 软删 P003
+	w := makeRequest(r, "DELETE", fmt.Sprintf("/api/v1/products/%d", lastID), token, nil)
+	require.Equal(t, http.StatusOK, w.Code)
+
+	// 再建 → 必须是 P004，不能复用已软删的 P003
+	w = makeRequest(r, "POST", "/api/v1/products", token, map[string]interface{}{
+		"name": "NR new", "unit": "个",
+	})
+	require.Equal(t, http.StatusCreated, w.Code)
+	data := parseResponse(w)["data"].(map[string]interface{})
+	assert.Equal(t, "P004", data["code"])
+}
+
+// (shop_id, code) 唯一约束生效，且重复被翻译成 gorm.ErrDuplicatedKey（Create/FindOrCreate 重试的前提）。
+func TestProductHandler_UniqueShopCode(t *testing.T) {
+	db := testutil.SetupTestDB()
+	shop := testutil.CreateTestShop(db, "UQ001")
+	require.NoError(t, db.Exec("CREATE UNIQUE INDEX uk_shop_code ON products(shop_id, code)").Error)
+
+	p1 := model.Product{TenantBase: model.TenantBase{ShopID: shop.ID}, Name: "A", Code: "P001"}
+	require.NoError(t, db.Create(&p1).Error)
+
+	p2 := model.Product{TenantBase: model.TenantBase{ShopID: shop.ID}, Name: "B", Code: "P001"}
+	err := db.Create(&p2).Error
+	require.Error(t, err)
+	assert.True(t, errors.Is(err, gorm.ErrDuplicatedKey))
+}

backend/internal/model/product.go

@@ -10,6 +10,8 @@ type ProductCategory struct {
 type Product struct {
 	TenantBase
 	PublicID      string  `gorm:"size:36;uniqueIndex" json:"public_id"`
+	// Code 商品编码：同店内唯一。(shop_id, code) 联合唯一索引 uk_shop_code 由 autoMigrate 显式建（见 main.go），
+	// 不在此用 tag 声明——ShopID 在共用 TenantBase 上，tag 只能建单列索引会破坏多租户隔离。
 	Code          string  `gorm:"size:50" json:"code"`
 	Barcode       string  `gorm:"size:100" json:"barcode"`
 	Name          string  `gorm:"size:200;not null" json:"name"`

backend/main.go

@@ -87,7 +87,8 @@ func initDB() *gorm.DB {
 	}
 
 	db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{
-		Logger: logger.Default.LogMode(logLevel),
+		Logger:         logger.Default.LogMode(logLevel),
+		TranslateError: true, // 把 MySQL 1062 翻译成 gorm.ErrDuplicatedKey，供编码撞唯一约束时重试
 	})
 	if err != nil {
 		log.Fatalf("failed to connect database: %v", err)
@@ -136,5 +137,12 @@ func autoMigrate(db *gorm.DB) {
 	if err != nil {
 		log.Fatalf("auto migrate failed: %v", err)
 	}
+	// products(shop_id, code) 联合唯一索引：ShopID 在共用 TenantBase 上无法用 struct tag 表达，
+	// 故在此幂等显式建（保证同店内商品编码唯一，DB 层兜底防止重复编码静默落库）。
+	if !db.Migrator().HasIndex(&model.Product{}, "uk_shop_code") {
+		if err := db.Exec("CREATE UNIQUE INDEX uk_shop_code ON products (shop_id, code)").Error; err != nil {
+			log.Fatalf("create unique index uk_shop_code failed: %v", err)
+		}
+	}
 	log.Println("AutoMigrate completed")
 }

backend/testutil/setup.go

@@ -46,7 +46,8 @@ func SetupTestDB() *gorm.DB {
 	InitConfig()
 
 	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{
-		Logger: logger.Default.LogMode(logger.Silent),
+		Logger:         logger.Default.LogMode(logger.Silent),
+		TranslateError: true,
 	})
 	if err != nil {
 		panic(fmt.Sprintf("failed to open sqlite: %v", err))