[FIX] stock: scrap insufficient qty bypass UoM

Usecase to reproduce:
- Set 1 unit of product A in stock
- Scrap 1 dozen of product A

Warning message for Insufficient Quantity is not triggered.

It happens because there is no UoM conversion between scrap qty and
product quant quantity.

Fixes #30570

closes odoo/odoo#30589

addons/stock/models/stock_scrap.py

@@ -130,7 +130,8 @@ class StockScrap(models.Model):
                                                             self.package_id,
                                                             self.owner_id,
                                                             strict=True).mapped('quantity'))
-        if float_compare(available_qty, self.scrap_qty, precision_digits=precision) >= 0:
+        scrap_qty = self.product_uom_id._compute_quantity(self.scrap_qty, self.product_id.uom_id)
+        if float_compare(available_qty, scrap_qty, precision_digits=precision) >= 0:
             return self.do_scrap()
         else:
             return {

addons/stock/tests/test_move.py

@@ -3424,6 +3424,24 @@ class StockMove(TransactionCase):
         self.assertEqual(scrap.state, 'done')
         self.assertEqual(move1.reserved_availability, 0.25)
 
+    def test_scrap_6(self):
+        """ Check that scrap correctly handle UoM. """
+        self.env['stock.quant']._update_available_quantity(self.product1, self.stock_location, 1)
+        scrap = self.env['stock.scrap'].create({
+            'product_id': self.product1.id,
+            'product_uom_id': self.uom_dozen.id,
+            'scrap_qty': 1,
+        })
+        warning_message = scrap.action_validate()
+        self.assertEqual(warning_message.get('res_model', 'Wrong Model'), 'stock.warn.insufficient.qty.scrap')
+        insufficient_qty_wizard = self.env['stock.warn.insufficient.qty.scrap'].create({
+            'product_id': self.product1.id,
+            'location_id': self.stock_location.id,
+            'scrap_id': scrap.id
+        })
+        insufficient_qty_wizard.action_done()
+        self.assertEqual(self.env['stock.quant']._gather(self.product1, self.stock_location).quantity, -11)
+
     def test_in_date_1(self):
         """ Check that moving a tracked quant keeps the incoming date.
         """