Fixed some bugs in django/contrib/sites/managers and added some error checking

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2961 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/sites/managers.py

@@ -1,11 +1,26 @@
-from django.db import models
 from django.conf import settings
+from django.db import models
+from django.db.models.fields import FieldDoesNotExist
 
 class CurrentSiteManager(models.Manager):
     "Use this to limit objects to those associated with the current site."
-    def __init__(self, field_name='site')
-        super(SiteLimitManager, self).__init__()
-        self.__lookup = field_name + '__id__exact'
+    def __init__(self, field_name='site'):
+        super(CurrentSiteManager, self).__init__()
+        self.__field_name = field_name
+
+    def contribute_to_class(self, *args, **kwargs):
+        # This method is overridden purely to check for errors in
+        # self.field_name. We can't do this in __init__() because of
+        # how Managers are implemented -- self.model isn't available
+        # until after contribute_to_class() is called.
+        super(CurrentSiteManager, self).contribute_to_class(*args, **kwargs)
+        try:
+            self.model._meta.get_field(self.__field_name)
+        except FieldDoesNotExist:
+            raise ValueError, "%s couldn't find a field named %s in %s." % \
+                (self.__class__.__name__, self.__field_name, self.model._meta.object_name)
+        self.__lookup = self.__field_name + '__id__exact'
+        del self.__field_name
 
     def get_query_set(self):
-        return super(SiteLimitManager, self).get_query_set().filter(self.__lookup=settings.SITE_ID)
+        return super(SiteLimitManager, self).get_query_set().filter(**{self.__lookup: settings.SITE_ID})