Remove Admin's swallowing of AttributeError (#16655, #18593, #18747)

During the new-admin changes, catching of AttributeError was added to
the admin.  This patch removes that as it's no longer possible to add a
value to a ModelAdmin that is not available.  Adding an attribute that
can not be called causes an ImproperlyConfigured exception to be raised.

django/contrib/admin/templatetags/admin_list.py

@@ -182,7 +182,7 @@ def items_for_result(cl, result, form):
         row_class = ''
         try:
             f, attr, value = lookup_field(field_name, result, cl.model_admin)
-        except (AttributeError, ObjectDoesNotExist):
+        except ObjectDoesNotExist:
             result_repr = EMPTY_CHANGELIST_VALUE
         else:
             if f is None:

tests/regressiontests/admin_views/admin.py

@@ -27,11 +27,14 @@ from .models import (Article, Chapter, Account, Media, Child, Parent, Picture,
     Album, Question, Answer, ComplexSortedPerson, PrePopulatedPostLargeSlug,
     AdminOrderedField, AdminOrderedModelMethod, AdminOrderedAdminMethod,
     AdminOrderedCallable, Report, Color2, UnorderedObject, MainPrepopulated,
-    RelatedPrepopulated, UndeletableObject)
+    RelatedPrepopulated, UndeletableObject, Simple)
 
 
 def callable_year(dt_value):
+    try:
         return dt_value.year
+    except AttributeError:
+        return None
 callable_year.admin_order_field = 'date'
 
 
@@ -575,6 +578,14 @@ class UndeletableObjectAdmin(admin.ModelAdmin):
         return super(UndeletableObjectAdmin, self).change_view(*args, **kwargs)
 
 
+def callable_on_unknown(obj):
+    return obj.unknown
+
+
+class AttributeErrorRaisingAdmin(admin.ModelAdmin):
+    list_display = [callable_on_unknown, ]
+
+
 site = admin.AdminSite(name="admin")
 site.register(Article, ArticleAdmin)
 site.register(CustomArticle, CustomArticleAdmin)
@@ -648,6 +659,7 @@ site.register(AdminOrderedModelMethod, AdminOrderedModelMethodAdmin)
 site.register(AdminOrderedAdminMethod, AdminOrderedAdminMethodAdmin)
 site.register(AdminOrderedCallable, AdminOrderedCallableAdmin)
 site.register(Color2, CustomTemplateFilterColorAdmin)
+site.register(Simple, AttributeErrorRaisingAdmin)
 
 # Register core models we need in our tests
 from django.contrib.auth.models import User, Group

tests/regressiontests/admin_views/customadmin.py

@@ -49,3 +49,4 @@ site.register(models.Fabric, base_admin.FabricAdmin)
 site.register(models.ChapterXtra1, base_admin.ChapterXtra1Admin)
 site.register(User, UserLimitedAdmin)
 site.register(models.UndeletableObject, base_admin.UndeletableObjectAdmin)
+site.register(models.Simple, base_admin.AttributeErrorRaisingAdmin)

tests/regressiontests/admin_views/models.py

@@ -649,3 +649,9 @@ class UndeletableObject(models.Model):
     Refs #10057.
     """
     name = models.CharField(max_length=255)
+
+
+class Simple(models.Model):
+    """
+    Simple model with nothing on it for use in testing
+    """

tests/regressiontests/admin_views/tests.py

@@ -46,7 +46,7 @@ from .models import (Article, BarAccount, CustomArticle, EmptyModel, FooAccount,
     OtherStory, ComplexSortedPerson, Parent, Child, AdminOrderedField,
     AdminOrderedModelMethod, AdminOrderedAdminMethod, AdminOrderedCallable,
     Report, MainPrepopulated, RelatedPrepopulated, UnorderedObject,
-    UndeletableObject)
+    Simple, UndeletableObject)
 
 
 ERROR_MESSAGE = "Please enter the correct username and password \
@@ -578,6 +578,20 @@ class AdminViewBasicTest(TestCase):
                                    (self.urlbit, instance.pk))
         self.assertNotContains(response, 'deletelink')
 
+    def test_allows_attributeerror_to_bubble_up(self):
+        """
+        Ensure that AttributeErrors are allowed to bubble when raised inside
+        a change list view.
+
+        Requires a model to be created so there's something to be displayed
+
+        Refs: #16655, #18593, and #18747
+        """
+        Simple.objects.create()
+        with self.assertRaises(AttributeError):
+            self.client.get('/test_admin/%s/admin_views/simple/' % self.urlbit)
+
+
 @override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
 class AdminViewFormUrlTest(TestCase):
     urls = "regressiontests.admin_views.urls"