Fixed #12550 -- better handling with choices and null fields when displaying read-only values

Thanks Jacques Beaurain for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12148 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/admin/util.py

@@ -281,7 +281,12 @@ def label_for_field(name, model, model_admin):
 def display_for_field(value, field):
     from django.contrib.admin.templatetags.admin_list import _boolean_icon
     from django.contrib.admin.views.main import EMPTY_CHANGELIST_VALUE
-    if isinstance(field, models.DateField) or isinstance(field, models.TimeField):
+
+    if field.flatchoices:
+        return dict(field.flatchoices).get(value, EMPTY_CHANGELIST_VALUE)
+    elif value is None:
+        return EMPTY_CHANGELIST_VALUE
+    elif isinstance(field, models.DateField) or isinstance(field, models.TimeField):
         return formats.localize(value)
     elif isinstance(field, models.BooleanField) or isinstance(field, models.NullBooleanField):
         return _boolean_icon(value)
@@ -289,7 +294,5 @@ def display_for_field(value, field):
         return formats.number_format(value, field.decimal_places)
     elif isinstance(field, models.FloatField):
         return formats.number_format(value)
-    elif field.flatchoices:
-        return dict(field.flatchoices).get(value, EMPTY_CHANGELIST_VALUE)
     else:
         return smart_unicode(value)

tests/regressiontests/admin_util/models.py

+# needed for tests
\ No newline at end of file

tests/regressiontests/admin_util/tests.py

+import unittest
+
+from django.db import models
+
+from django.contrib import admin
+from django.contrib.admin.util import display_for_field
+from django.contrib.admin.views.main import EMPTY_CHANGELIST_VALUE
+
+
+
+class UtilTests(unittest.TestCase):
+    def test_null_display_for_field(self):
+        """
+        Regression test for #12550: display_for_field should handle None
+        value.
+        """
+        display_value = display_for_field(None, models.CharField())
+        self.assertEqual(display_value, EMPTY_CHANGELIST_VALUE)
+
+        display_value = display_for_field(None, models.CharField(
+            choices=(
+                (None, "test_none"),
+            )
+        ))
+        self.assertEqual(display_value, "test_none")
+
+        display_value = display_for_field(None, models.DateField())
+        self.assertEqual(display_value, EMPTY_CHANGELIST_VALUE)
+
+        display_value = display_for_field(None, models.TimeField())
+        self.assertEqual(display_value, EMPTY_CHANGELIST_VALUE)
+
+        display_value = display_for_field(None, models.NullBooleanField())
+        self.assertEqual(display_value, EMPTY_CHANGELIST_VALUE)
+
+        display_value = display_for_field(None, models.DecimalField())
+        self.assertEqual(display_value, EMPTY_CHANGELIST_VALUE)
+
+        display_value = display_for_field(None, models.FloatField())
+        self.assertEqual(display_value, EMPTY_CHANGELIST_VALUE)