[FIX] purchase_stock: update the PO qty without traceback

Steps to reproduce the bug:
- Create a storable product X1:
    - Route: MTO + buy
    - Vendor: Azure Interior
    - BoM:
        - Type: subcontractor
        - Subcontractor: Azure interior
        - Component: any component

- Create a MO:
    - product: P1
    - Component: X1, qty: 3
- Confirm the MO
- Go to the created PO
- Confirm the PO

- Go to the picking
- receive 2 units of P1 and validate it
- create a backorder
- Cancel the backorder
- Try to update the purchased qty in the PO line to 2

Problem:
A traceback is triggered:
File "/home/odoo/src/odoo/addons/purchase_stock/models/purchase.py", line 542, in _prepare_stock_move_vals
'picking_id': picking.id,
AttributeError: 'bool' object has no attribute 'id'

Solution:
When updating the quantity in the purchase order, if no picking requires
an update, it is better to avoid creating a new picking and new moves.

opw-3681064

closes odoo/odoo#152577

X-original-commit: 0da5d6cc0c94320ad39fe9b930dde4b0ef6feff5
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: Djamel Touati (otd) <otd@odoo.com>

addons/mrp_subcontracting_purchase/tests/test_mrp_subcontracting_purchase.py

@@ -621,16 +621,28 @@ class MrpSubcontractingPurchaseTest(TestMrpSubcontractingCommon):
         """
         Test That we can update the quantity of a purchase order line with a subcontracted product
         """
-        po = self.env['purchase.order'].create({
-            'partner_id': self.subcontractor_partner1.id,
-            'order_line': [Command.create({
-                'name': 'finished',
-                'product_id': self.finished.id,
-                'product_qty': 3.0,
-                'product_uom': self.finished.uom_id.id,
-                'price_unit': 50.0}
-            )],
+        mto_route = self.env.ref('stock.route_warehouse0_mto')
+        buy_route = self.env['stock.route'].search([('name', '=', 'Buy')])
+        mto_route.active = True
+        self.finished.route_ids = mto_route.ids + buy_route.ids
+        seller = self.env['product.supplierinfo'].create({
+            'partner_id': self.vendor.id,
+            'price': 12.0,
+            'delay': 0
         })
+        self.finished.seller_ids = [(6, 0, [seller.id])]
+
+        mo = self.env['mrp.production'].create({
+            'product_id': self.finished2.id,
+            'product_qty': 3.0,
+            'move_raw_ids': [(0, 0, {
+                'product_id': self.finished.id,
+                'product_uom_qty': 3.0,
+                'product_uom': self.finished.uom_id.id,
+            })]
+        })
+        mo.action_confirm()
+        po = self.env['purchase.order.line'].search([('product_id', '=', self.finished.id)]).order_id
         po.button_confirm()
         self.assertEqual(len(po.picking_ids), 1)
         picking = po.picking_ids

addons/purchase_stock/models/purchase_order_line.py

@@ -174,7 +174,9 @@ class PurchaseOrderLine(models.Model):
                 # If the user increased quantity of existing line or created a new line
                 pickings = line.order_id.picking_ids.filtered(lambda x: x.state not in ('done', 'cancel') and x.location_dest_id.usage in ('internal', 'transit', 'customer'))
                 picking = pickings and pickings[0] or False
-                if not picking and line.product_qty > line.qty_received:
+                if not picking:
+                    if not line.product_qty > line.qty_received:
+                        continue
                     res = line.order_id._prepare_picking()
                     picking = self.env['stock.picking'].create(res)