[FIX] stock: don't update a move line with qty=1 with serial product

Use case to reproduce:
- create a product A with serial number
- add 2 product A in stock
- create a delivery order with this 4 product
- Check Availability
- add 2 more product A in stock
- Check Availability
- in the first line the quantity is now 3

It happens because _update_reserved_quantity on stock move
try to add the quantity reserved on simililar move lines.
Howevever in serial case we don't want to have a move line
with a reserved quantity greater than 1.

addons/stock/models/stock_move.py

@@ -816,7 +816,8 @@ class StockMove(models.Model):
 
         # Find a candidate move line to update or create a new one.
         for reserved_quant, quantity in quants:
-            to_update = self.move_line_ids.filtered(lambda m: m.location_id.id == reserved_quant.location_id.id and m.lot_id.id == reserved_quant.lot_id.id and m.package_id.id == reserved_quant.package_id.id and m.owner_id.id == reserved_quant.owner_id.id)
+            to_update = self.move_line_ids.filtered(lambda m: m.product_id.tracking != 'serial' and
+                                                    m.location_id.id == reserved_quant.location_id.id and m.lot_id.id == reserved_quant.lot_id.id and m.package_id.id == reserved_quant.package_id.id and m.owner_id.id == reserved_quant.owner_id.id)
             if to_update:
                 to_update[0].with_context(bypass_reservation_update=True).product_uom_qty += self.product_id.uom_id._compute_quantity(quantity, self.product_uom, rounding_method='HALF-UP')
             else:

addons/stock/tests/test_move.py

@@ -756,6 +756,28 @@ class StockMove(TransactionCase):
         self.assertEqual(customer_quants.quantity, 30)
         self.assertEqual(customer_quants.reserved_quantity, 0)
 
+    def test_availability_5(self):
+        """ Check that rerun action assign only create new stock move
+        lines instead of adding quantity in existing one.
+        """
+        self.env['stock.quant']._update_available_quantity(self.product2, self.stock_location, 2.0)
+        # move from shelf1
+        move = self.env['stock.move'].create({
+            'name': 'test_edit_moveline_1',
+            'location_id': self.stock_location.id,
+            'location_dest_id': self.customer_location.id,
+            'product_id': self.product2.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 4.0,
+        })
+        move._action_confirm()
+        move._action_assign()
+
+        self.env['stock.quant']._update_available_quantity(self.product2, self.stock_location, 4.0)
+        move._action_assign()
+
+        self.assertEqual(len(move.move_line_ids), 4.0)
+
     def test_unreserve_1(self):
         """ Check that unreserving a stock move sets the products reserved as available and
         set the state back to confirmed.