[FIX] stock: block updating uom factor if reserved moves.

This commit block users to change unit of measure factor. if there are
reserved move on product using this UoM. This will allow the quantities
to be correctly unreserved when the stock move will be confirmed.

Task id : 1844684

addons/stock/models/product.py

@@ -583,3 +583,23 @@ class ProductCategory(models.Model):
             category = category.parent_id
             routes |= category.route_ids
         self.total_route_ids = routes
+
+
+class ProductUoM(models.Model):
+    _inherit = 'product.uom'
+
+    def write(self, values):
+        # Users can not update the factor if open stock moves are based on it
+        if 'factor' in values or 'factor_inv' in values or 'category_id' in values:
+            stock_move_lines = self.env['stock.move.line'].search_count([
+                ('product_uom_id.category_id', '=', self.category_id.id),
+                ('state', '!=', 'cancel'),
+            ])
+
+            if stock_move_lines:
+                raise UserError(_(
+                    "You cannot change the ratio of this unit of mesure as some"
+                    " products with this UoM have already been moved or are "
+                    "currently reserved."
+                ))
+        return super(ProductUoM, self).write(values)

addons/stock/tests/__init__.py

@@ -9,3 +9,4 @@ from . import test_quant
 from . import test_inventory
 from . import test_move
 from . import test_move2
+from . import test_robustness

addons/stock/tests/test_robustness.py

@@ -0,0 +1,65 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from odoo.exceptions import UserError
+from odoo.tests.common import TransactionCase
+
+
+class TestRobustness(TransactionCase):
+    def setUp(self):
+        super(TestRobustness, self).setUp()
+        self.stock_location = self.env.ref('stock.stock_location_stock')
+        self.customer_location = self.env.ref('stock.stock_location_customers')
+        self.uom_unit = self.env.ref('product.product_uom_unit')
+        self.uom_dozen = self.env.ref('product.product_uom_dozen')
+        self.product1 = self.env['product.product'].create({
+            'name': 'Product A',
+            'type': 'product',
+            'categ_id': self.env.ref('product.product_category_all').id,
+        })
+
+    def test_uom_factor(self):
+        """ Changing the factor of a unit of measure shouldn't be allowed while
+        quantities are reserved, else the existing move lines won't be consistent
+        with the `reserved_quantity` on quants.
+        """
+        # make some stock
+        self.env['stock.quant']._update_available_quantity(
+            self.product1,
+            self.stock_location,
+            12,
+        )
+
+        # reserve a dozen
+        move1 = self.env['stock.move'].create({
+            'name': 'test_uom_rounding',
+            'location_id': self.stock_location.id,
+            'location_dest_id': self.customer_location.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_dozen.id,
+            'product_uom_qty': 1,
+        })
+        move1._action_confirm()
+        move1._action_assign()
+        self.assertEqual(move1.state, 'assigned')
+        quant = self.env['stock.quant']._gather(
+            self.product1,
+            self.stock_location,
+        )
+
+        # assert the reservation
+        self.assertEqual(quant.reserved_quantity, 12)
+        self.assertEqual(move1.product_qty, 12)
+
+        # change the factor
+        with self.assertRaises(UserError):
+            with self.cr.savepoint():
+                move1.product_uom.factor = 0.05
+
+        # assert the reservation
+        self.assertEqual(quant.reserved_quantity, 12)
+        self.assertEqual(move1.state, 'assigned')
+        self.assertEqual(move1.product_qty, 12)
+
+        # unreserve
+        move1._do_unreserve()