[IMP] sale: Use a cache to compute fiscal positions

addons/sale/models/sale_order.py

@@ -403,7 +403,7 @@ class SaleOrder(models.Model):
             if not order.partner_id:
                 order.fiscal_position_id = False
                 continue
-            key = (order.company_id, order.partner_id, order.partner_shipping_id)
+            key = (order.company_id.id, order.partner_id.id, order.partner_shipping_id.id)
             if key not in cache:
                 cache[key] = self.env['account.fiscal.position'].with_company(
                     order.company_id

addons/sale/models/sale_order_line.py

@@ -139,9 +139,12 @@ class SaleOrderLine(models.Model):
 
     @api.depends('product_id')
     def _compute_tax_id(self):
+        cached_fpos = {}
         for line in self:
             line = line.with_company(line.company_id)
-            fpos = line.order_id.fiscal_position_id or line.order_id.fiscal_position_id._get_fiscal_position(line.order_partner_id)
+            if line.order_id not in cached_fpos:
+                cached_fpos[line.order_id] = line.order_id.fiscal_position_id or line.order_id.fiscal_position_id._get_fiscal_position(line.order_partner_id)
+            fpos = cached_fpos[line.order_id]
             # If company_id is set, always filter taxes by the company
             taxes = line.product_id.taxes_id.filtered(lambda t: t.company_id == line.env.company)
             line.tax_id = fpos.map_tax(taxes)