[FIX] stock: set correct return quantity

Steps to reproduce:
-Enable multistep routes for manufacturing
-create a MO for 50 products
-In internal transfers from Stock to Pre-production validate
part of the tansfer (20 units) and create a back order
for the remaining qty (30 units)
-create and validate another pertail transfer (3 units)with a back order
for the remaining quantity (27 units)
-create a return for the last validated transfers

Bug:
the default qty for the return is set to -20 where it should be 3
this commit[1] deducts the previous transfers from the returned amount

Fix:
only deduct returns from current transfer

opw-3104699
[1]:https://github.com/odoo/odoo/commit/7b08f0ae0a39e8f575b21e744de16264b6365704

closes odoo/odoo#115929

X-original-commit: 0278a4a7ba5cdd7a722e5d576d22820a3ee64308
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: Walid Hanniche (waha) <waha@odoo.com>

addons/sale_stock/tests/test_sale_stock.py

@@ -1232,6 +1232,37 @@ class TestSaleStock(TestSaleCommon, ValuationReconciliationTestCommon):
         self.assertEqual(so.order_line[1].qty_delivered, 1)
         self.assertEqual(so.order_line[1].product_uom.id, uom_km_id)
 
+    def test_multiple_returns(self):
+        # Creates a sale order for 10 products.
+        sale_order = self._get_new_sale_order()
+        # Valids the sale order, then valids the delivery.
+        sale_order.action_confirm()
+        picking = sale_order.picking_ids
+        picking.move_ids.write({'quantity_done': 10})
+        picking.button_validate()
+
+        # Creates a return from the delivery picking.
+        return_picking_form = Form(self.env['stock.return.picking']
+            .with_context(active_ids=picking.ids, active_id=picking.id,
+            active_model='stock.picking'))
+        return_wizard = return_picking_form.save()
+        # Check that the correct quantity is set on the retrun
+        self.assertEqual(return_wizard.product_return_moves.quantity, 10)
+        return_wizard.product_return_moves.quantity = 2
+        # Valids the return picking.
+        res = return_wizard.create_returns()
+        return_picking = self.env['stock.picking'].browse(res['res_id'])
+        return_picking.move_ids.write({'quantity_done': 2})
+        return_picking.button_validate()
+
+        # Creates a second return from the delivery picking.
+        return_picking_form = Form(self.env['stock.return.picking']
+            .with_context(active_ids=picking.ids, active_id=picking.id,
+            active_model='stock.picking'))
+        return_wizard = return_picking_form.save()
+        # Check that the remaining quantity is set on the retrun
+        self.assertEqual(return_wizard.product_return_moves.quantity, 8)
+
     def test_return_with_mto_and_multisteps(self):
         """
         Suppose a product P and a 3-steps delivery.

addons/stock/wizard/stock_picking_return.py

@@ -79,7 +79,7 @@ class ReturnPicking(models.TransientModel):
     def _prepare_stock_return_picking_line_vals_from_move(self, stock_move):
         quantity = stock_move.product_qty
         for move in stock_move.move_dest_ids:
-            if move.origin_returned_move_id and move.origin_returned_move_id != stock_move:
+            if not move.origin_returned_move_id or move.origin_returned_move_id != stock_move:
                 continue
             if move.state in ('partially_available', 'assigned'):
                 quantity -= sum(move.move_line_ids.mapped('reserved_qty'))