[FIX] purchase: _anglo_saxon_purchase_move_lines

Let's consider a stockable product P with a product category PC with costing method = real price,
valuation = perpetual, stock valuation account = SVA and price diff account = PDA.
The cost defined for P in product.template is equal to 1$.

Steps

-Create a PO for P with a price unit = 5$
-Confirm PO and generate the invoice
-Update the qty for P in the invoice and validate it(price unit is still 5$)

Bug:

In the general ledger: a move with a debit of 1$ is created for SVA and a debit of 4$
is created for PDA which is wrong. The expected result is: just a move of 5$ created
for SVA and nothing for PDA because the difference between the purchase price and the
invoiced price is 0.

This commit fixes this problem.

NB: in real price and average price, the considered cost must be the purchase price
and not the cost defined in the product template.

opw:740879

addons/purchase/models/account_invoice.py

@@ -144,6 +144,7 @@ class AccountInvoice(models.Model):
                     valuation_price_unit = i_line.product_id.uom_id._compute_price(i_line.product_id.standard_price, i_line.uom_id)
                     if i_line.product_id.cost_method != 'standard' and i_line.purchase_line_id:
                         #for average/fifo/lifo costing method, fetch real cost price from incomming moves
+                        valuation_price_unit = i_line.purchase_line_id.product_uom._compute_price(i_line.purchase_line_id.price_unit, i_line.uom_id)
                         stock_move_obj = self.env['stock.move']
                         valuation_stock_move = stock_move_obj.search([('purchase_line_id', '=', i_line.purchase_line_id.id), ('state', '=', 'done')])
                         if valuation_stock_move: