From to + pricing component

modules/purchase_trade/pricing.py

@@ -2,7 +2,7 @@
 # this repository contains the full copyright notices and license terms.
 from trytond.model import fields
 from trytond.pool import Pool, PoolMeta
-from trytond.pyson import Bool, Eval, Id
+from trytond.pyson import Bool, Eval, Id, If
 from trytond.model import (ModelSQL, ModelView)
 from trytond.exceptions import UserError
 from trytond.tools import is_full_text, lstrip_wildcard
@@ -333,11 +333,11 @@ class Pricing(ModelSQL,ModelView):
     pricing_date = fields.Date("Date")
     price_component = fields.Many2One(
         'pricing.component', "Component",
-        domain=[
-            'OR',
-            ('line', '=', Eval('line', -1)),
-            ('sale_line', '=', Eval('sale_line', -1)),
-        ],
+        domain=[If(Bool(Eval('line')),
+            ('line', '=', Eval('line')),
+            If(Bool(Eval('sale_line')),
+                ('sale_line', '=', Eval('sale_line')),
+                ('id', '=', -1)))],
         depends=['line', 'sale_line'])#, ondelete='CASCADE')
     quantity = fields.Numeric("Qt",digits='unit')
     settl_price = fields.Numeric("Settl. price",digits='unit')