added default_adaptor to ItemAdaptor

--HG--
extra : convert_revision : svn%3Ab85faa78-f9eb-468e-a121-7cced6da292c%40947

scrapy/trunk/scrapy/contrib_exp/newitem/adaptors.py

@@ -20,6 +20,7 @@ class ItemAdaptor(object):
         self.item_instance = item if item else self.item_class()
         self._response = response
         self._field_adaptors = self._get_field_adaptors()
+        self._default_adaptor = self._get_default_adaptor()
 
     def _get_field_adaptors(self):
         fa = {}
@@ -31,14 +32,24 @@ class ItemAdaptor(object):
 
         return fa
 
+    def _get_default_adaptor(self):
+        try:
+            return object.__getattribute__(self, 'default_adaptor')
+        except:
+            return None
+
     def __setattr__(self, name, value):
-        if name.startswith('_') or name == 'item_instance':
+        if name.startswith('_') or name == 'item_instance' \
+                or name == 'default_adaptor':
             return object.__setattr__(self, name, value)
 
         try:
             fa = self._field_adaptors[name]
         except KeyError:
-            return setattr(self.item_instance, name, value)
+            if self._default_adaptor:
+                fa = self._default_adaptor
+            else:
+                return setattr(self.item_instance, name, value)
 
         adaptor_args = {'response': self._response}
         ovalue = fa(value, adaptor_args=adaptor_args)

scrapy/trunk/scrapy/tests/test_itemadaptor.py

@@ -23,6 +23,16 @@ class ItemAdaptorTest(unittest.TestCase):
         self.assertEqual(ia.item_instance.name, 'Marta')
         self.assertEqual(ia.name, 'Marta')
 
+    def test_defaultadaptor(self):
+        class DefaultedTestAdaptor(ItemAdaptor):
+            item_class = TestItem
+            default_adaptor = lambda v, adaptor_args: v.title()
+
+        dta = DefaultedTestAdaptor()
+        assert dta._default_adaptor
+        dta.name = 'marta'
+        assert dta.name == 'Marta'
+
     def test_inheritance(self):
         class ChildTestAdaptor(TestAdaptor):
             url = lambda v, adaptor_args: v.lower()