Fixed deferred loading of fields with default values.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10113 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/base.py

@@ -272,14 +272,14 @@ class Model(object):
 
         for field in fields_iter:
             is_related_object = False
-            if kwargs:
             # This slightly odd construct is so that we can access any
-                # data-descriptor object (DeferredAttribute) without triggering
-                # its __get__ method.
+            # data-descriptor object (DeferredAttribute) without triggering its
+            # __get__ method.
             if (field.attname not in kwargs and
                     isinstance(self.__class__.__dict__.get(field.attname), DeferredAttribute)):
                 # This field will be populated on request.
                 continue
+            if kwargs:
                 if isinstance(field.rel, ManyToOneRel):
                     try:
                         # Assume object instance was passed in.

tests/regressiontests/defer_regress/models.py

@@ -0,0 +1,47 @@
+"""
+Regression tests for defer() / only() behavior.
+"""
+
+from django.conf import settings
+from django.db import connection, models
+
+class Item(models.Model):
+    name = models.CharField(max_length=10)
+    text = models.TextField(default="xyzzy")
+    value = models.IntegerField()
+    other_value = models.IntegerField(default=0)
+
+    def __unicode__(self):
+        return self.name
+
+__test__ = {"regression_tests": """
+Deferred fields should really be deferred and not accidentally use the field's
+default value just because they aren't passed to __init__.
+
+>>> settings.DEBUG = True
+>>> _ = Item.objects.create(name="first", value=42)
+>>> obj = Item.objects.only("name", "other_value").get(name="first")
+
+# Accessing "name" doesn't trigger a new database query. Accessing "value" or
+# "text" should.
+>>> num = len(connection.queries)
+>>> obj.name
+u"first"
+>>> obj.other_value
+0
+>>> len(connection.queries) == num
+True
+>>> obj.value
+42
+>>> len(connection.queries) == num + 1      # Effect of values lookup.
+True
+>>> obj.text
+u"xyzzy"
+>>> len(connection.queries) == num + 2      # Effect of text lookup.
+True
+
+>>> settings.DEBUG = False
+
+"""
+}
+