fix(order): persist cleared courier tracking numbers

order/src/main/java/com/baiyue/order/entity/OrderEntity.java

@@ -64,6 +64,8 @@ public class OrderEntity extends BaseEntity {
     private Long rootOrderId;
     private Integer splitSequence;
     private String expressCompany;
+    // 客户清空单号或改用其他交货方式时，必须把 NULL 写入数据库。
+    @TableField(updateStrategy = FieldStrategy.ALWAYS)
     private String expressTrackingNo;
     private LocalDateTime submittedAt;
     private LocalDateTime completedAt;

order/src/test/java/com/baiyue/order/service/MerchantOrderCommandTransactionTest.java

@@ -44,6 +44,30 @@ class MerchantOrderCommandTransactionTest {
     private OrderRequests.SaveRequest draft;
     private com.baiyue.order.client.FirstlegInboundClient firstleg;
 
+    /** 通过真实 MyBatis 和内存数据库验证单号更新及清空，避免空值被更新策略忽略。 */
+    @Test
+    void courierTrackingCanBeClearedAndSwitchingPickupMethodClearsItInDatabase() {
+        var fields = (com.fasterxml.jackson.databind.node.ObjectNode) json.valueToTree(draft);
+        fields.remove("carrierSnapshotComplete");
+        fields.put("expressTrackingNo", "  SF-ORIGINAL  ");
+        var filled = json.convertValue(fields, OrderRequests.SaveRequest.class);
+        long id = service.createDraft(11L, 7L, "operator", filled, "courier-create");
+        assertThat(db.queryForObject("SELECT express_tracking_no FROM ord_order WHERE id=?", String.class, id))
+            .isEqualTo("SF-ORIGINAL");
+
+        fields.remove("expressTrackingNo");
+        var blank = json.convertValue(fields, OrderRequests.SaveRequest.class);
+        service.updateDraft(11L, 7L, id, new OrderRequests.DraftUpdateRequest(0, blank), "courier-clear");
+        assertThat(db.queryForObject("SELECT express_tracking_no FROM ord_order WHERE id=?", String.class, id)).isNull();
+
+        service.updateDraft(11L, 7L, id, new OrderRequests.DraftUpdateRequest(1, filled), "courier-restore");
+        fields.put("pickupMethod", "SELF_TRUCK");
+        fields.put("expressTrackingNo", "SPOOFED");
+        var truck = json.convertValue(fields, OrderRequests.SaveRequest.class);
+        service.updateDraft(11L, 7L, id, new OrderRequests.DraftUpdateRequest(2, truck), "courier-switch");
+        assertThat(db.queryForObject("SELECT express_tracking_no FROM ord_order WHERE id=?", String.class, id)).isNull();
+    }
+
     @BeforeEach
     void prepare() throws Exception {
         JdbcDataSource source = new JdbcDataSource();