Do not browse records at a datetime before they were created

If user tries to get the cost price of a product before it was created, it
should return None instead of raising an access error.

issue7334
review49281002

location.py

@@ -378,24 +378,25 @@ class Location(DeactivableMixin, ModelSQL, ModelView):
         if not any(map(valid_context, ['product', 'product_template'])):
             return cost_values
 
+        def get_record():
+            if trans_context.get('product') is not None:
+                return Product(trans_context['product'])
+            else:
+                return Template(trans_context['product_template'])
+
         context = {}
         if 'stock_date_end' in trans_context:
             # Use the last cost_price of the day
             context['_datetime'] = datetime.datetime.combine(
                 trans_context['stock_date_end'], datetime.time.max)
-        with Transaction().set_context(context):
-
-            if trans_context.get('product') is not None:
-                product = Product(trans_context['product'])
-                cost_price = product.cost_price
-            else:
-                template = Template(trans_context['product_template'])
-                cost_price = template.cost_price
             # The date could be before the product creation
-            # or the template may have more than one product
-            if not isinstance(cost_price, Decimal):
+            record = get_record()
+            if record.create_date > context['_datetime']:
                 return cost_values
-
+        with Transaction().set_context(context):
+            cost_price = get_record().cost_price
+        # The template may have more than one product
+        if cost_price is not None:
             for location in locations:
                 cost_values[location.id] = (
                     Decimal(str(location.quantity)) * cost_price)

product.py

@@ -136,21 +136,22 @@ class Product(StockMixin, object):
 
     @classmethod
     def get_cost_value(cls, products, name):
-        cost_values = {}
+        cost_values = {p.id: None for p in products}
         context = {}
         trans_context = Transaction().context
         if trans_context.get('stock_date_end'):
             # Use the last cost_price of the day
             context['_datetime'] = datetime.datetime.combine(
                 trans_context['stock_date_end'], datetime.time.max)
+            # The date could be before the product creation
+            products = [p for p in products
+                if p.create_date <= context['_datetime']]
         with Transaction().set_context(context):
             for product in cls.browse(products):
-                # The date could be before the product creation
-                if not isinstance(product.cost_price, Decimal):
-                    cost_values[product.id] = None
-                else:
-                    cost_values[product.id] = (Decimal(str(product.quantity))
-                        * product.cost_price)
+                # The product may not have a cost price
+                if product.cost_price is not None:
+                    cost_values[product.id] = (
+                        Decimal(str(product.quantity)) * product.cost_price)
         return cost_values
 
     @classmethod