[REF] stock_account: cost method changes

When changing the costing method for a FIFO product to AVCO or standard,
we update the standard price of the product to the average cost in
stock.

2 files changed, 153 insertions, 5 deletions

diff --git a/addons/stock_account/models/product.py b/addons/stock_account/models/product.py
index d35299cf0a6..10d80789938 100644
--- a/addons/stock_account/models/product.py
+++ b/addons/stock_account/models/product.py
@@ -58,6 +58,15 @@ class ProductTemplate(models.Model):
 
     @api.one
     def _set_cost_method(self):
+        # When going from FIFO to AVCO or to standard, we update the standard price with the
+        # average value in stock.
+        if self.property_cost_method == 'fifo' and self.cost_method in ['average', 'standard']:
+            # Cannot use the `stock_value` computed field as it's already invalidated when
+            # entering this method.
+            valuation = sum([variant._sum_remaining_values() for variant in self.product_variant_ids])
+            qty_available = self.with_context(company_owned=True).qty_available
+            if qty_available:
+                self.standard_price = valuation / qty_available
         return self.write({'property_cost_method': self.cost_method})
 
     @api.multi
@@ -158,17 +167,20 @@ class ProductProduct(models.Model):
         candidates = self.env['stock.move'].search(domain, order='date, id')
         return candidates
 
+    def _sum_remaining_values(self):
+        StockMove = self.env['stock.move']
+        domain = [('product_id', '=', self.id)] + StockMove._get_all_base_domain()
+        moves = StockMove.search(domain)
+        return sum(moves.mapped('remaining_value'))
+
     @api.multi
-    @api.depends('stock_move_ids.product_qty', 'stock_move_ids.state')
+    @api.depends('stock_move_ids.product_qty', 'stock_move_ids.state', 'product_tmpl_id.cost_method')
     def _compute_stock_value(self):
         for product in self:
             if product.cost_method in ['standard', 'average']:
                 product.stock_value = product.standard_price * product.with_context(company_owned=True).qty_available
             elif product.cost_method == 'fifo':
-                StockMove = self.env['stock.move']
-                domain = [('product_id', '=', product.id)] + StockMove._get_all_base_domain()
-                moves = StockMove.search(domain)
-                product.stock_value = sum(moves.mapped('remaining_value'))
+                product.stock_value = product._sum_remaining_values()
 
     @api.multi
     def action_open_product_moves(self):
diff --git a/addons/stock_account/tests/test_stockvaluation.py b/addons/stock_account/tests/test_stockvaluation.py
index ab8cae3b905..3059e927acc 100644
--- a/addons/stock_account/tests/test_stockvaluation.py
+++ b/addons/stock_account/tests/test_stockvaluation.py
@@ -2149,3 +2149,139 @@ class TestStockValuation(TransactionCase):
 
         self.assertEqual(move7.value, 100.0)
         self.assertEqual(self.product1.standard_price, 10)
+
+    def test_change_cost_method_1(self):
+        """ Change the cost method from FIFO to AVCO.
+        """
+        # ---------------------------------------------------------------------
+        # Use FIFO, make some operations
+        # ---------------------------------------------------------------------
+        self.product1.product_tmpl_id.cost_method = 'fifo'
+
+        # receive 10@10
+        move1 = self.env['stock.move'].create({
+            'name': '10 units @ 10.00 per unit',
+            'location_id': self.supplier_location.id,
+            'location_dest_id': self.stock_location.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 10.0,
+            'price_unit': 10,
+        })
+        move1._action_confirm()
+        move1._action_assign()
+        move1.move_line_ids.qty_done = 10.0
+        move1._action_done()
+
+        # receive 10@15
+        move2 = self.env['stock.move'].create({
+            'name': '10 units @ 10.00 per unit',
+            'location_id': self.supplier_location.id,
+            'location_dest_id': self.stock_location.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 10.0,
+            'price_unit': 15,
+        })
+        move2._action_confirm()
+        move2._action_assign()
+        move2.move_line_ids.qty_done = 10.0
+        move2._action_done()
+
+        # sell 1
+        move3 = self.env['stock.move'].create({
+            'name': 'Sale 5 units',
+            'location_id': self.stock_location.id,
+            'location_dest_id': self.customer_location.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 1.0,
+        })
+        move3._action_confirm()
+        move3._action_assign()
+        move3.move_line_ids.qty_done = 1.0
+        move3._action_done()
+
+        self.assertEqual(self.product1.stock_value, 240)
+
+        # ---------------------------------------------------------------------
+        # Change the production valuation to AVCO
+        # ---------------------------------------------------------------------
+        self.product1.with_context(debug=True).product_tmpl_id.cost_method = 'average'
+
+        # valuation should stay to ~240
+        self.assertAlmostEqual(self.product1.stock_value, 240, delta=0.03)
+
+        # no accounting entry should be created
+
+        # the cost should now be 12,65
+        # (9 * 10) + (15 * 10) / 19
+        self.assertEqual(self.product1.standard_price, 12.63)
+
+    def test_change_cost_method_2(self):
+        """ Change the cost method from FIFO to standard.
+        """
+        # ---------------------------------------------------------------------
+        # Use FIFO, make some operations
+        # ---------------------------------------------------------------------
+        self.product1.product_tmpl_id.cost_method = 'fifo'
+
+        # receive 10@10
+        move1 = self.env['stock.move'].create({
+            'name': '10 units @ 10.00 per unit',
+            'location_id': self.supplier_location.id,
+            'location_dest_id': self.stock_location.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 10.0,
+            'price_unit': 10,
+        })
+        move1._action_confirm()
+        move1._action_assign()
+        move1.move_line_ids.qty_done = 10.0
+        move1._action_done()
+
+        # receive 10@15
+        move2 = self.env['stock.move'].create({
+            'name': '10 units @ 10.00 per unit',
+            'location_id': self.supplier_location.id,
+            'location_dest_id': self.stock_location.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 10.0,
+            'price_unit': 15,
+        })
+        move2._action_confirm()
+        move2._action_assign()
+        move2.move_line_ids.qty_done = 10.0
+        move2._action_done()
+
+        # sell 1
+        move3 = self.env['stock.move'].create({
+            'name': 'Sale 5 units',
+            'location_id': self.stock_location.id,
+            'location_dest_id': self.customer_location.id,
+            'product_id': self.product1.id,
+            'product_uom': self.uom_unit.id,
+            'product_uom_qty': 1.0,
+        })
+        move3._action_confirm()
+        move3._action_assign()
+        move3.move_line_ids.qty_done = 1.0
+        move3._action_done()
+
+        self.assertEqual(self.product1.stock_value, 240)
+
+        # ---------------------------------------------------------------------
+        # Change the production valuation to AVCO
+        # ---------------------------------------------------------------------
+        self.product1.with_context(debug=True).product_tmpl_id.cost_method = 'standard'
+
+        # valuation should stay to ~240
+        self.assertAlmostEqual(self.product1.stock_value, 240, delta=0.03)
+
+        # no accounting entry should be created
+
+        # the cost should now be 12,65
+        # (9 * 10) + (15 * 10) / 19
+        self.assertEqual(self.product1.standard_price, 12.63)
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