Fixed #21924 -- Added the ability to specify a reverse order for admin_order_field.

Thanks Klemens Mantzos for the report and initial patch.

django/contrib/admin/views/main.py

@@ -293,7 +293,11 @@ class ChangeList(six.with_metaclass(RenameChangeListMethods)):
                     order_field = self.get_ordering_field(field_name)
                     if not order_field:
                         continue  # No 'admin_order_field', skip it
-                    ordering.append(pfx + order_field)
+                    # reverse order if order_field has already "-" as prefix
+                    if order_field.startswith('-') and pfx == "-":
+                        ordering.append(order_field[1:])
+                    else:
+                        ordering.append(pfx + order_field)
                 except (IndexError, ValueError):
                     continue  # Invalid ordering specified, skip it.
 

docs/ref/contrib/admin/index.txt

@@ -664,6 +664,14 @@ subclass::
       The above will tell Django to order by the ``first_name`` field when
       trying to sort by ``colored_first_name`` in the admin.
 
+      .. versionadded:: 1.7
+
+      To indicate descending order with ``admin_model_field`` you can use a
+      hyphen prefix on the field name. Using the above example, this would
+      look like::
+
+          colored_first_name.admin_order_field = '-first_name'
+
     * Elements of ``list_display`` can also be properties. Please note however,
       that due to the way properties work in Python, setting
       ``short_description`` on a property is only possible when using the

docs/releases/1.7.txt

@@ -292,6 +292,10 @@ Minor features
   <django.contrib.admin.ModelAdmin.view_on_site>` to control whether or not to
   display the "View on site" link.
 
+* You can specify a descending ordering for a :attr:`ModelAdmin.list_display
+  <django.contrib.admin.ModelAdmin.list_display>` value by prefixing the
+  ``admin_order_field`` value with a hyphen.
+
 :mod:`django.contrib.auth`
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 

tests/admin_views/admin.py

@@ -76,7 +76,8 @@ class ChapterXtra1Admin(admin.ModelAdmin):
 
 
 class ArticleAdmin(admin.ModelAdmin):
-    list_display = ('content', 'date', callable_year, 'model_year', 'modeladmin_year')
+    list_display = ('content', 'date', callable_year, 'model_year',
+                    'modeladmin_year', 'model_year_reversed')
     list_filter = ('date', 'section')
     view_on_site = False
     fieldsets = (

tests/admin_views/models.py

@@ -41,6 +41,11 @@ class Article(models.Model):
     model_year.admin_order_field = 'date'
     model_year.short_description = ''
 
+    def model_year_reversed(self):
+        return self.date.year
+    model_year_reversed.admin_order_field = '-date'
+    model_year_reversed.short_description = ''
+
 
 @python_2_unicode_compatible
 class Book(models.Model):

tests/admin_views/tests.py

@@ -260,7 +260,7 @@ class AdminViewBasicTest(AdminViewBasicTestCase):
     def testChangeListSortingModelAdmin(self):
         """
         Ensure we can sort on a list_display field that is a ModelAdmin method
-        (colunn 4 is 'modeladmin_year' in ArticleAdmin)
+        (column 4 is 'modeladmin_year' in ArticleAdmin)
         """
         response = self.client.get('/test_admin/%s/admin_views/article/' % self.urlbit, {'o': '4'})
         self.assertContentBefore(response, 'Oldest content', 'Middle content',
@@ -268,6 +268,25 @@ class AdminViewBasicTest(AdminViewBasicTestCase):
         self.assertContentBefore(response, 'Middle content', 'Newest content',
             "Results of sorting on ModelAdmin method are out of order.")
 
+    def testChangeListSortingModelAdminReverse(self):
+        """
+        Ensure we can sort on a list_display field that is a ModelAdmin
+        method in reverse order (i.e. admin_order_field uses the '-' prefix)
+        (column 6 is 'model_year_reverse' in ArticleAdmin)
+        """
+        response = self.client.get('/test_admin/%s/admin_views/article/' % self.urlbit, {'o': '6'})
+        self.assertContentBefore(response, '2009', '2008',
+            "Results of sorting on ModelAdmin method are out of order.")
+        self.assertContentBefore(response, '2008', '2000',
+            "Results of sorting on ModelAdmin method are out of order.")
+        # Let's make sure the ordering is right and that we don't get a
+        # FieldError when we change to descending order
+        response = self.client.get('/test_admin/%s/admin_views/article/' % self.urlbit, {'o': '-6'})
+        self.assertContentBefore(response, '2000', '2008',
+            "Results of sorting on ModelAdmin method are out of order.")
+        self.assertContentBefore(response, '2008', '2009',
+            "Results of sorting on ModelAdmin method are out of order.")
+
     def testChangeListSortingMultiple(self):
         p1 = Person.objects.create(name="Chris", gender=1, alive=True)
         p2 = Person.objects.create(name="Chris", gender=2, alive=True)