support default values on fields (and models)

import_export/fields.py

@@ -4,6 +4,7 @@
 
 from django.core.exceptions import ObjectDoesNotExist
 from django.db.models.manager import Manager
+from django.db.models.fields import NOT_PROVIDED
 
 
 class Field(object):
@@ -22,11 +23,14 @@ class Field(object):
 
     ``readonly`` boolean value defines that if this field will be assigned
     to object during import.
+
+    ``default`` value returned by :meth`clean` if returned value evaluates to False
     """
 
     def __init__(self, attribute=None, column_name=None, widget=None,
-            readonly=False):
+                 default=None, readonly=False):
         self.attribute = attribute
+        self.default = default
         self.column_name = column_name
         if not widget:
             widget = widgets.Widget()
@@ -59,6 +63,11 @@ def clean(self, data):
         except ValueError as e:
             raise ValueError("Column '%s': %s" % (self.column_name, e))
 
+        if not value and self.default != NOT_PROVIDED:
+            if callable(self.default):
+                self.default = self.default()
+            return self.default
+
         return value
 
     def get_value(self, obj):

import_export/resources.py

@@ -139,7 +139,7 @@ def __new__(cls, name, bases, attrs):
 
         # Add direct options
         options = getattr(new_class, 'Meta', None)
-        for option in [option for option in dir(options) 
+        for option in [option for option in dir(options)
                        if not option.startswith('_')]:
             setattr(meta, option, getattr(options, option))
         new_class._meta = meta
@@ -569,8 +569,13 @@ def field_from_django_field(self, field_name, django_field, readonly):
 
         FieldWidget = self.widget_from_django_field(django_field)
         widget_kwargs = self.widget_kwargs_for_field(field_name)
-        field = Field(attribute=field_name, column_name=field_name,
-                widget=FieldWidget(**widget_kwargs), readonly=readonly)
+        field = Field(
+            attribute=field_name,
+            column_name=field_name,
+            widget=FieldWidget(**widget_kwargs),
+            readonly=readonly,
+            default=django_field.default,
+        )
         return field
 
     def get_import_id_fields(self):
@@ -598,4 +603,3 @@ def modelresource_factory(model, resource_class=ModelResource):
 
     metaclass = ModelDeclarativeMetaclass
     return metaclass(class_name, (resource_class,), class_attrs)
-

tests/core/models.py

@@ -43,3 +43,7 @@ class Profile(models.Model):
 
 class Entry(models.Model):
     user = models.ForeignKey('auth.User')
+
+
+class WithDefault(models.Model):
+    name = models.CharField('Default', max_length=75, blank=True, default=lambda: 'foo_bar')

tests/core/tests/resources_tests.py

@@ -23,7 +23,7 @@
 from import_export import results
 from import_export.instance_loaders import ModelInstanceLoader
 
-from core.models import Book, Author, Category, Entry, Profile
+from core.models import Book, Author, Category, Entry, Profile, WithDefault
 
 try:
     from django.utils.encoding import force_text
@@ -115,6 +115,12 @@ class Meta:
         exclude = ('imported', )
 
 
+class WithDefaultResource(resources.ModelResource):
+    class Meta:
+        model = WithDefault
+        fields = ('name',)
+
+
 class ModelResourceTest(TestCase):
     def setUp(self):
         self.resource = BookResource()
@@ -154,6 +160,10 @@ def test_init_instance(self):
         instance = self.resource.init_instance()
         self.assertIsInstance(instance, Book)
 
+    def test_default(self):
+        self.assertTrue(callable(WithDefaultResource.fields['name'].default))
+        self.assertEquals(WithDefaultResource.fields['name'].clean({'name': ''}), 'foo_bar')
+
     def test_get_instance(self):
         instance_loader = self.resource._meta.instance_loader_class(
                 self.resource)