Fix db engine (#32351)

Fix #32349

models/db/context_test.go

@@ -84,3 +84,47 @@ func TestTxContext(t *testing.T) {
 		}))
 	}
 }
+
+func TestContextSafety(t *testing.T) {
+	type TestModel1 struct {
+		ID int64
+	}
+	type TestModel2 struct {
+		ID int64
+	}
+	assert.NoError(t, unittest.GetXORMEngine().Sync(&TestModel1{}, &TestModel2{}))
+	assert.NoError(t, db.TruncateBeans(db.DefaultContext, &TestModel1{}, &TestModel2{}))
+	testCount := 10
+	for i := 1; i <= testCount; i++ {
+		assert.NoError(t, db.Insert(db.DefaultContext, &TestModel1{ID: int64(i)}))
+		assert.NoError(t, db.Insert(db.DefaultContext, &TestModel2{ID: int64(-i)}))
+	}
+
+	actualCount := 0
+	// here: db.GetEngine(db.DefaultContext) is a new *Session created from *Engine
+	_ = db.WithTx(db.DefaultContext, func(ctx context.Context) error {
+		_ = db.GetEngine(ctx).Iterate(&TestModel1{}, func(i int, bean any) error {
+			// here: db.GetEngine(ctx) is always the unclosed "Iterate" *Session with autoResetStatement=false,
+			// and the internal states (including "cond" and others) are always there and not be reset in this callback.
+			m1 := bean.(*TestModel1)
+			assert.EqualValues(t, i+1, m1.ID)
+
+			// here: XORM bug, it fails because the SQL becomes "WHERE id=-1", "WHERE id=-1 AND id=-2", "WHERE id=-1 AND id=-2 AND id=-3" ...
+			// and it conflicts with the "Iterate"'s internal states.
+			// has, err := db.GetEngine(ctx).Get(&TestModel2{ID: -m1.ID})
+
+			actualCount++
+			return nil
+		})
+		return nil
+	})
+	assert.EqualValues(t, testCount, actualCount)
+
+	// deny the bad usages
+	assert.PanicsWithError(t, "using database context in an iterator would cause corrupted results", func() {
+		_ = unittest.GetXORMEngine().Iterate(&TestModel1{}, func(i int, bean any) error {
+			_ = db.GetEngine(db.DefaultContext)
+			return nil
+		})
+	})
+}