backend/app/services/no_generator.py

@@ -8,7 +8,7 @@
 
 from datetime import datetime
 
-from sqlalchemy import select
+from sqlalchemy import func, select
 from sqlalchemy.orm import Session
 
 
@@ -35,10 +35,13 @@ def next_no(
     """
     like_prefix = today_prefix(prefix)
     column = getattr(model, column_name)
+    # 排序按「长度优先、同级字典序」：同前缀下序号位数增多（9999→10000）后
+    # 纯字典序会反转（"-10000" < "-9999"，'1'<'9'），seq 将恒重算出同一号码、
+    # 每笔建单都撞唯一键 —— 长度大即数值大，同级同长时字典序与数值序一致
     max_no = session.execute(
         select(column)
         .where(column.like(f"{like_prefix}%"))
-        .order_by(column.desc())
+        .order_by(func.length(column).desc(), column.desc())
         .limit(1)
         .with_for_update()
     ).scalar()

backend/tests/integration/test_no_generator.py

@@ -0,0 +1,82 @@
+"""单据编号生成器的跨位宽正确性（no_generator）。
+
+守：当日序号超过 4 位宽度（9999→10000）后，VARCHAR 字典序排序会失效
+（"-10000" < "-9999"，'1'<'9'）——MAX 检索若按纯字典序，seq 会恒重算出
+同一号码，每笔建单都撞唯一键。修复口径：长度优先、同级按字典序
+（同前缀下长度大即数值大；同长时字典序与数值序一致）。
+"""
+
+import pytest
+from sqlalchemy import select
+
+from app.core.constants import NO_PREFIX_BUSINESS
+from app.core.db import get_session_factory
+from app.models import Business, Customer
+from app.services.no_generator import next_no, today_prefix
+
+pytestmark = pytest.mark.integration
+
+
+def _insert_business_nos(nos: list[str]) -> None:
+    """直插同日前缀的业务编号行（仅编号用于 MAX 检索；其余列取默认/可空）。
+
+    直插绕过服务层（服务层走完整创建链太重），业务行为挂在 t_ 客户名下，
+    由 integration/conftest 兜底清理（YW% 单据 + t\\_% 客户）。
+    """
+    factory = get_session_factory()
+    with factory() as session:
+        customer = Customer(
+            company_name="t_no_generator_client",
+            owner_name="t_no_generator_owner",
+            customer_type="enterprise",
+        )
+        session.add(customer)
+        session.flush()
+        session.add_all(Business(business_no=no, customer_id=customer.id) for no in nos)
+        session.commit()
+
+
+class TestMaxCrossWidth:
+    """MAX 检索在同日前缀下跨位宽取最大序号。"""
+
+    def test_序号破四位宽后仍按数值取最大(self) -> None:
+        """4 位与 5 位并存："-9999" 字典序大于 "-10000"，纯字典序会取错。"""
+        prefix = today_prefix(NO_PREFIX_BUSINESS)
+        _insert_business_nos([f"{prefix}9999", f"{prefix}10000"])
+        factory = get_session_factory()
+        with factory() as session:
+            no = next_no(
+                session, model=Business, column_name="business_no", prefix=NO_PREFIX_BUSINESS
+            )
+        assert no == f"{prefix}10001"
+
+    def test_同位宽内字典序与数值序一致仍取最大(self) -> None:
+        """同宽多行（修复的排序不破坏原行为）：是长度优先而非只按长度取首行。"""
+        prefix = today_prefix(NO_PREFIX_BUSINESS)
+        _insert_business_nos([f"{prefix}0099", f"{prefix}8499", f"{prefix}8500"])
+        factory = get_session_factory()
+        with factory() as session:
+            no = next_no(
+                session, model=Business, column_name="business_no", prefix=NO_PREFIX_BUSINESS
+            )
+        assert no == f"{prefix}8501"
+
+    def test_无当日编号时从1起编(self) -> None:
+        """当日无同前缀行（昨日编号不被 like 命中）：从 0001 起，不受历史天数影响。
+
+        当日若已有其他用例留下的同前缀编号（用例间无隔离库），跳过——
+        空表场景由每次 `down -v` 重建后的首个用例覆盖。
+        """
+        prefix = today_prefix(NO_PREFIX_BUSINESS)
+        factory = get_session_factory()
+        with factory() as session:
+            existing = session.execute(
+                select(Business.id).where(Business.business_no.like(f"{prefix}%")).limit(1)
+            ).scalar()
+        if existing is not None:
+            pytest.skip(f"当日已有同前缀编号 {existing}，空表场景跳过")
+        with factory() as session:
+            no = next_no(
+                session, model=Business, column_name="business_no", prefix=NO_PREFIX_BUSINESS
+            )
+        assert no == f"{prefix}0001"