[FIX] stock: unreserve drop all the processed work

Usecase to reproduce(or any other way to lower initial demand on move):
- Build a MO with 5 products to do
- Produce 3
- Update the quantity on the mo to 3
-> All the consumed quantity on move lines is dropped.

It happens because lowering the initial demand on a move
will call unlink on its move lines. (increase it will
update the move's state and reassign if it comes from a supplier)

Instead of dropping and reassign the move in order to change
the reservation, it is possible to directly write the new
reserved quantity on the move lines and that will update the
reservation on qaunt directly. Also we don't want move lines
without reserved quantity and quantity done thus we drop them.

closes odoo/odoo#29941

addons/mrp/models/mrp_production.py

@@ -439,7 +439,10 @@ class MrpProduction(models.Model):
         move = self.move_raw_ids.filtered(lambda x: x.bom_line_id.id == bom_line.id and x.state not in ('done', 'cancel'))
         if move:
             if quantity > 0:
-                move[0].write({'product_uom_qty': quantity})
+                move[0]._decrease_reserved_quanity(quantity)
+                move[0].with_context(do_not_unreserve=True).write({'product_uom_qty': quantity})
+                move[0]._recompute_state()
+                move[0]._action_assign()
                 move.unit_factor = quantity / move.raw_material_production_id.product_qty
             elif quantity < 0:  # Do not remove 0 lines
                 if move[0].quantity_done > 0:

addons/mrp/models/stock_move.py

@@ -182,6 +182,24 @@ class StockMove(models.Model):
         self.sudo().unlink()
         return processed_moves
 
+    def _decrease_reserved_quanity(self, quantity):
+        """ Decrease the reservation on move lines but keeps the
+        all other data.
+        """
+        move_line_to_unlink = self.env['stock.move.line']
+        for move in self:
+            reserved_quantity = quantity
+            for move_line in self.move_line_ids:
+                if move_line.product_uom_qty > reserved_quantity:
+                    move_line.product_uom_qty = reserved_quantity
+                else:
+                    move_line.product_uom_qty = 0
+                    reserved_quantity -= move_line.product_uom_qty
+                if not move_line.product_uom_qty and not move_line.qty_done:
+                    move_line_to_unlink |= move_line
+        move_line_to_unlink.unlink()
+        return True
+
     def _prepare_phantom_move_values(self, bom_line, quantity):
         return {
             'picking_id': self.picking_id.id if self.picking_id else False,

addons/mrp/tests/test_order.py

@@ -617,3 +617,49 @@ class TestMrpOrder(TestMrpCommon):
 
         mo.button_mark_done()
         self.assertEqual(mo.state, 'done', "Production order should be in done state.")
+
+    def test_product_produce_5(self):
+        """ Build 5 final products with different consumed lots,
+        then edit the finished quantity and update the Manufacturing
+        order quantity. Then check if the produced quantity do not
+        change and it is possible to close the MO.
+        """
+        self.stock_location = self.env.ref('stock.stock_location_stock')
+        mo, bom, p_final, p1, p2 = self.generate_mo(tracking_base_1='lot')
+        self.assertEqual(len(mo), 1, 'MO should have been created')
+
+        lot_1 = self.env['stock.production.lot'].create({
+            'name': 'lot1',
+            'product_id': p1.id,
+        })
+        lot_2 = self.env['stock.production.lot'].create({
+            'name': 'lot2',
+            'product_id': p1.id,
+        })
+
+        self.env['stock.quant']._update_available_quantity(p1, self.stock_location, 10, lot_id=lot_1)
+        self.env['stock.quant']._update_available_quantity(p1, self.stock_location, 10, lot_id=lot_2)
+
+        self.env['stock.quant']._update_available_quantity(p2, self.stock_location, 5)
+        mo.action_assign()
+
+        produce_wizard = self.env['mrp.product.produce'].with_context({
+            'active_id': mo.id,
+            'active_ids': [mo.id],
+        }).create({
+            'product_qty': 5.0,
+        })
+
+        for produce_line in produce_wizard.produce_line_ids:
+            produce_line.qty_done = produce_line.qty_to_consume
+        produce_wizard.do_produce()
+
+        mo.move_finished_ids.move_line_ids.qty_done -= 1
+        update_quantity_wizard = self.env['change.production.qty'].create({
+            'mo_id': mo.id,
+            'product_qty': 4,
+        })
+        update_quantity_wizard.change_prod_qty()
+
+        self.assertEqual(mo.move_raw_ids.filtered(lambda m: m.product_id == p1).quantity_done, 20, 'Update the produce quantity should not impact already produced quantity.')
+        mo.button_mark_done()

addons/mrp/wizard/change_production_qty.py

@@ -50,7 +50,6 @@ class ChangeProductionQty(models.TransientModel):
             qty_produced = production.product_id.uom_id._compute_quantity(sum(done_moves.mapped('product_qty')), production.product_uom_id)
             factor = production.product_uom_id._compute_quantity(production.product_qty - qty_produced, production.bom_id.product_uom_id) / production.bom_id.product_qty
             boms, lines = production.bom_id.explode(production.product_id, factor, picking_type=production.bom_id.picking_type_id)
-            done_quantities = {move: move.quantity_done for move in production.move_raw_ids}
             for line, line_data in lines:
                 production._update_raw_move(line, line_data)
             operation_bom_qty = {}
@@ -60,9 +59,6 @@ class ChangeProductionQty(models.TransientModel):
             self._update_product_to_produce(production, production.product_qty - qty_produced)
             moves = production.move_raw_ids.filtered(lambda x: x.state not in ('done', 'cancel'))
             moves._action_assign()
-            for move in production.move_raw_ids:
-                if move.quantity_done != done_quantities[move]:
-                    move._set_quantity_done(done_quantities[move])
             for wo in production.workorder_ids:
                 operation = wo.operation_id
                 if operation_bom_qty.get(operation.id):