[FIX] l10n_it_delivery_note: allow validation of backorders

This fixes the following issue:

Steps to reproduce:

* create a SO with two lines and confirm it
* delivery partially only one of the two lines
* validate the backorder

Current behavior:

The backorder is not validated as stock_delivery_note_line_move_uniq constraint is raised

Expected behavior:

The backorder is validated

l10n_it_delivery_note/models/stock_picking.py

@@ -343,3 +343,11 @@ def write(self, vals):
                 self.mapped('delivery_note_id').update_detail_lines()
 
         return res
+
+    def _create_backorder(self):
+        """When we make a backorder of a picking the delivery note lines needed
+        to be updated otherwise stock_delivery_note_line_move_uniq
+        constraint is raised"""
+        backorders = super()._create_backorder()
+        for backorder in backorders:
+            backorder.backorder_id.delivery_note_id.update_detail_lines()

l10n_it_delivery_note/readme/CONTRIBUTORS.rst

@@ -7,3 +7,4 @@
 * Letizia Freda <[email protected]>
 * Andrea Piovesana <[email protected]>
 * Giovanni Serra <[email protected]>
+* Alex Comba <[email protected]>

l10n_it_delivery_note/tests/__init__.py

@@ -1,2 +1,3 @@
 from . import delivery_note_common
 from . import test_stock_delivery_note_invoicing
+from . import test_stock_delivery_note

l10n_it_delivery_note/tests/test_stock_delivery_note.py

@@ -0,0 +1,50 @@
+# Copyright 2021 Alex Comba - Agile Business Group
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+from .delivery_note_common import StockDeliveryNoteCommon
+
+
+class StockDeliveryNote(StockDeliveryNoteCommon):
+
+    # ⇒ "Ordine singolo: consegna parziale"
+    def test_partial_delivering_single_so(self):
+        #
+        #     SO ┐         ┌ DdT
+        #        ├ Picking ┘
+        #        │
+        #        └ Picking ┐
+        #                  └ DdT
+        #
+
+        # remove use_advanced_delivery_notes group in order to automatically
+        # create delivery note when picking is validated
+        use_adv_notes_group_id = self.env.ref(
+            "l10n_it_delivery_note.use_advanced_delivery_notes").id
+        self.env.user.write({'groups_id': [(3, use_adv_notes_group_id)]})
+
+        StockPicking = self.env["stock.picking"]
+        StockBackorderConfirmationWizard = self.env['stock.backorder.confirmation']
+        sales_order = self.create_sales_order(
+            [
+                self.large_desk_line,  # 1
+                self.desk_combination_line,  # 1
+            ],
+        )
+        self.assertEqual(len(sales_order.order_line), 2)
+        sales_order.action_confirm()
+        self.assertEqual(len(sales_order.picking_ids), 1)
+        picking = sales_order.picking_ids
+        self.assertEqual(len(picking.move_lines), 2)
+
+        # deliver only the first product
+        picking.move_lines[0].quantity_done = 1
+
+        backorder_wiz_id = picking.button_validate()['res_id']
+        backorder_wiz = StockBackorderConfirmationWizard.browse(backorder_wiz_id)
+        backorder_wiz.process()
+        self.assertTrue(picking.delivery_note_id)
+        picking_backorder = StockPicking.search([("backorder_id", "=", picking.id)])
+        self.assertEqual(len(picking_backorder.move_lines), 1)
+        picking_backorder.move_lines[0].quantity_done = 1
+        picking_backorder.button_validate()
+        self.assertTrue(picking_backorder.delivery_note_id)