[FIX] stock_account: valuation and costing method

In v9, the creation of a product doesn't set a `valuation` or a
`cost_method` by default. It means that the corresponding fields of the
product category is selected instead.

In v10, this is the other way around: a default value is set on these
fields, and therefore the value on the product is selected. This is
obviously a change in behavior, and moreover the field is invisible in
the product view, meaning that it cannot be changed.

This is due to the new API conversion. In the new API, the methods
`_compute_valuation_type` and `_compute_cost_method` are called through
the 'onchange' mechanism. This sets the associated fields, which are
then copied in their `property_` counterpart thanks to the inverse
function.

opw-691231

addons/stock_account/models/product.py

@@ -40,7 +40,7 @@ class ProductTemplate(models.Model):
     @api.one
     @api.depends('property_valuation', 'categ_id.property_valuation')
     def _compute_valuation_type(self):
-        self.valuation = self.property_valuation if self.property_valuation else self.categ_id.property_valuation
+        self.valuation = self.property_valuation or self.categ_id.property_valuation
 
     @api.one
     def _set_valuation_type(self):
@@ -49,7 +49,7 @@ class ProductTemplate(models.Model):
     @api.one
     @api.depends('property_cost_method', 'categ_id.property_cost_method')
     def _compute_cost_method(self):
-        self.cost_method = self.property_cost_method if self.property_cost_method else self.categ_id.property_cost_method
+        self.cost_method = self.property_cost_method or self.categ_id.property_cost_method
 
     @api.one
     def _set_cost_method(self):
@@ -57,9 +57,8 @@ class ProductTemplate(models.Model):
 
     @api.onchange('type')
     def onchange_type_valuation(self):
-        if self.type != 'product':
-            self.valuation = 'manual_periodic'
-        return {}
+        # TO REMOVE IN MASTER
+        pass
 
     @api.multi
     def _get_product_accounts(self):
@@ -90,9 +89,8 @@ class ProductProduct(models.Model):
 
     @api.onchange('type')
     def onchange_type_valuation(self):
-        if self.type != 'product':
-            self.valuation = 'manual_periodic'
-        return {}
+        # TO REMOVE IN MASTER
+        pass
 
     @api.multi
     def do_change_standard_price(self, new_price, account_id):

addons/stock_account/views/product_views.xml

@@ -33,8 +33,8 @@
             <field name="arch" type="xml">
                 <data>
                     <field name="list_price" position="after">
-                        <field name="valuation" invisible="1"/>
-                        <field name="cost_method" invisible="1"/>
+                        <field name="valuation" invisible="1" readonly="1"/>
+                        <field name="cost_method" invisible="1" readonly="1"/>
                         <field name="property_cost_method" groups="stock_account.group_inventory_valuation" invisible="1"/>
                     </field>
                     <field name="standard_price" position="replace">