better handling of default value in newitem

scrapy/contrib_exp/newitem/fields.py

@@ -6,7 +6,7 @@ import time
 
 class BaseField(object):
     def __init__(self, default=None):
-        self.default = default or self.to_python(None)
+        self._default = self.to_python(default) if default is not None else None
 
     def to_python(self, value):
         """
@@ -15,6 +15,10 @@ class BaseField(object):
         """
         return value
 
+    def get_default(self):
+        """Returns the default value for the field."""
+        return self._default
+
 
 class MultiValuedField(BaseField):
     def __init__(self, field_type, default=None):

scrapy/contrib_exp/newitem/models.py

@@ -44,7 +44,7 @@ class Item(ScrapedItem):
             return self._values[name]
         except KeyError:
             try:
-                return self.fields[name].default
+                return self.fields[name].get_default()
             except KeyError:
                 raise AttributeError(name)
 
@@ -54,3 +54,4 @@ class Item(ScrapedItem):
         """
         values = dict((field, getattr(self, field)) for field in self.fields)
         return "%s(%s)" % (self.__class__.__name__, repr(values))
+

scrapy/tests/test_newitem.py

@@ -63,6 +63,13 @@ class NewItemTest(unittest.TestCase):
         i = TestItem()
         assert i.name == u'John'
 
+    def test_wrong_default(self):
+        def set_wrong_default():
+            class TestItem(Item):
+                name = fields.TextField(default=3)
+        
+        self.assertRaises(ValueError, set_wrong_default)
+
     def test_to_python_iter(self):
         class TestItem(Item):
             name = fields.TextField()
@@ -117,7 +124,7 @@ class NewItemFieldsTest(unittest.TestCase):
     def test_base_field(self):
         f = fields.BaseField()
 
-        assert f.default == None
+        assert f.get_default() is None
         assert f.to_python(1) == 1
 
     def test_boolean_field(self):