[FIX] mrp: unit_factor computation

Updating the quantity to produce in a production order will recompute
each raw move's unit factor. The issue was this computation did not
take care of the previously product quantity. The unit factor was wrong
and so the next created workorder lines get the wrong quantity.

Example:
  - 1 components for 1 finished product (unit_factor = 1)
  - Create a production for 2 finished product -> quantity to consume = 2
  - Produce 1 then change quantity to produce to 3 -> quantity to consume = 3
    and quantity done = 1 but unit factor became 1.5

closes odoo/odoo#40990

X-original-commit: 79976600df45afc6150150734eef405fd41a70a3
Signed-off-by: William Henrotin <Whenrow@users.noreply.github.com>

addons/mrp/models/mrp_production.py

@@ -625,7 +625,7 @@ class MrpProduction(models.Model):
                 move[0].with_context(do_not_unreserve=True).write({'product_uom_qty': quantity})
                 move[0]._recompute_state()
                 move[0]._action_assign()
-                move[0].unit_factor = remaining_qty and quantity / remaining_qty or 1.0
+                move[0].unit_factor = remaining_qty and (quantity - move[0].quantity_done) / remaining_qty or 1.0
                 return move[0], old_qty, quantity
             else:
                 if move[0].quantity_done > 0:

addons/mrp/tests/test_order.py

@@ -363,6 +363,42 @@ class TestMrpOrder(TestMrpCommon):
         self.assertEqual(sum(mo.move_raw_ids.filtered(lambda m: m.product_id == p1).mapped('quantity_done')), 20)
         self.assertEqual(sum(mo.move_finished_ids.mapped('quantity_done')), 5)
 
+    def test_update_quantity_3(self):
+        """ Build 1 final products then update the Manufacturing
+        order quantity. Check the remaining quantity to produce
+        take care of the first quantity produced."""
+        self.stock_location = self.env.ref('stock.stock_location_stock')
+        mo, bom, p_final, p1, p2 = self.generate_mo(qty_final=2)
+        self.assertEqual(len(mo), 1, 'MO should have been created')
+
+        self.env['stock.quant']._update_available_quantity(p1, self.stock_location, 20)
+        self.env['stock.quant']._update_available_quantity(p2, self.stock_location, 5)
+        mo.action_assign()
+
+        produce_form = Form(self.env['mrp.product.produce'].with_context({
+            'active_id': mo.id,
+            'active_ids': [mo.id],
+        }))
+        produce_form.qty_producing = 1
+        produce_wizard = produce_form.save()
+        produce_wizard.do_produce()
+
+        update_quantity_wizard = self.env['change.production.qty'].create({
+            'mo_id': mo.id,
+            'product_qty': 3,
+        })
+        update_quantity_wizard.change_prod_qty()
+
+        produce_form = Form(self.env['mrp.product.produce'].with_context({
+            'active_id': mo.id,
+            'active_ids': [mo.id],
+        }))
+        produce_wizard = produce_form.save()
+        produce_wizard.do_produce()
+        mo.button_mark_done()
+        self.assertEqual(sum(mo.move_raw_ids.filtered(lambda m: m.product_id == p1).mapped('quantity_done')), 12)
+        self.assertEqual(sum(mo.move_finished_ids.mapped('quantity_done')), 3)
+
     def test_rounding(self):
         """ Checks we round up when bringing goods to produce and round half-up when producing.
         This implementation allows to implement an efficiency notion (see rev 347f140fe63612ee05e).