[FIX] mrp: wrong use of self

The method _workorder_line_ids() is defined on mrp.workorder while `self`
is an instance of change_production_qty wizard in this case. Without this
commit, changing the quantity to produce of a manufactoring order with workorders
already planned raised a traceback.

addons/mrp/tests/test_workorder_operation.py

@@ -827,3 +827,26 @@ class TestWorkOrderProcess(TestMrpCommon):
         # Check that the workorder is planned now and that it lasts one hour
         self.assertEqual(workorder.date_planned_start, date_start, msg="Workorder should be planned tomorrow.")
         self.assertEqual(workorder.date_planned_finished, date_start + timedelta(hours=1), msg="Workorder should be done one hour later.")
+
+    def test_change_production_1(self):
+        """Change the quantity to produce on the MO while workorders are already planned."""
+        dining_table = self.env.ref("mrp.product_product_computer_desk")
+        dining_table.tracking = 'lot'
+        production_table_form = Form(self.env['mrp.production'])
+        production_table_form.product_id = dining_table
+        production_table_form.bom_id = self.env.ref("mrp.mrp_bom_desk")
+        production_table_form.product_qty = 1.0
+        production_table_form.product_uom_id = dining_table.uom_id
+        production_table = production_table_form.save()
+        production_table.action_confirm()
+
+        # Create work order
+        production_table.button_plan()
+
+        context = {'active_id': production_table.id, 'active_model': 'mrp.production'}
+        change_qty_form = Form(self.env['change.production.qty'].with_context(context))
+        change_qty_form.product_qty = 2.00
+        change_qty = change_qty_form.save()
+        change_qty.change_prod_qty()
+
+        self.assertEqual(production_table.workorder_ids[0].qty_producing, 2, "Quantity to produce not updated")

addons/mrp/wizard/change_production_qty.py

@@ -106,7 +106,7 @@ class ChangeProductionQty(models.TransientModel):
                 (moves_finished + moves_raw).write({'workorder_id': wo.id})
                 if wo.state not in ('done', 'cancel'):
                     line_values = wo._update_workorder_lines()
-                    self._workorder_line_ids().create(line_values['to_create'])
+                    wo._workorder_line_ids().create(line_values['to_create'])
                     if line_values['to_delete']:
                         line_values['to_delete'].unlink()
                     for line, vals in line_values['to_update'].items():