Fixing #26524 -- Made a foreign key id reference in ModelAdmin.list_display display the id.

django/contrib/admin/utils.py

@@ -19,6 +19,11 @@ from django.utils.text import capfirst
 from django.utils.translation import ungettext
 
 
+class FieldIsAForeignKeyColumnName(Exception):
+    """A field is a foreign key attname, i.e. <FK>_id."""
+    pass
+
+
 def lookup_needs_distinct(opts, lookup_path):
     """
     Returns True if 'distinct()' should be used to query the given lookup path.
@@ -272,7 +277,7 @@ def lookup_field(name, obj, model_admin=None):
     opts = obj._meta
     try:
         f = _get_non_gfk_field(opts, name)
-    except FieldDoesNotExist:
+    except (FieldDoesNotExist, FieldIsAForeignKeyColumnName):
         # For non-field values, the value is either a method, property or
         # returned via a callable.
         if callable(name):
@@ -310,6 +315,11 @@ def _get_non_gfk_field(opts, name):
             # Generic foreign keys OR reverse relations
             ((field.many_to_one and not field.related_model) or field.one_to_many)):
         raise FieldDoesNotExist()
+
+    # Avoid coercing <FK>_id fields to FK
+    if field.is_relation and hasattr(field, 'attname') and field.attname == name:
+        raise FieldIsAForeignKeyColumnName()
+
     return field
 
 
@@ -362,6 +372,10 @@ def label_for_field(name, model, model_admin=None, return_attr=False):
                     label = pretty_name(attr.__name__)
             else:
                 label = pretty_name(name)
+    except FieldIsAForeignKeyColumnName:
+        label = pretty_name(name)
+        attr = name
+
     if return_attr:
         return (label, attr)
     else:
@@ -372,7 +386,7 @@ def help_text_for_field(name, model):
     help_text = ""
     try:
         field = _get_non_gfk_field(model._meta, name)
-    except FieldDoesNotExist:
+    except (FieldDoesNotExist, FieldIsAForeignKeyColumnName):
         pass
     else:
         if hasattr(field, 'help_text'):

django/contrib/admin/views/main.py

@@ -371,6 +371,9 @@ class ChangeList(object):
                 pass
             else:
                 if isinstance(field.remote_field, models.ManyToOneRel):
+                    # <FK>_id field names don't require a join.
+                    if field_name == field.get_attname():
+                        continue
                     return True
         return False
 

docs/releases/1.11.txt

@@ -253,6 +253,10 @@ Miscellaneous
 * CSRF failures are logged to the ``django.security.csrf ``` logger instead of
   ``django.request``.
 
+* Using a foreign key's id (e.g. ``'field_id'``) in ``ModelAdmin.list_display``
+  displays the related object's ID instead of ``repr(object)``. Remove the
+  ``_id`` suffix if you want the ``repr()``.
+
 .. _deprecated-features-1.11:
 
 Features deprecated in 1.11

tests/admin_utils/tests.py

@@ -259,6 +259,7 @@ class UtilsTests(SimpleTestCase):
             label_for_field(lambda x: "nothing", Article),
             "--"
         )
+        self.assertEqual(label_for_field('site_id', Article), 'Site id')
 
         class MockModelAdmin(object):
             def test_from_model(self, obj):

tests/admin_views/tests.py

@@ -538,6 +538,18 @@ class AdminViewBasicTest(AdminViewBasicTestCase):
             self.assertContentBefore(response, 'The First Item', 'The Middle Item')
             self.assertContentBefore(response, 'The Middle Item', 'The Last Item')
 
+    def test_has_related_field_in_list_display(self):
+        """Joins shouldn't be performed for <FK>_id fields in list display."""
+        state = State.objects.create(name='Karnataka')
+        City.objects.create(state=state, name='Bangalore')
+        response = self.client.get(reverse('admin:admin_views_city_changelist'), {})
+
+        response.context['cl'].list_display = ['id', 'name', 'state']
+        self.assertEqual(response.context['cl'].has_related_field_in_list_display(), True)
+
+        response.context['cl'].list_display = ['id', 'name', 'state_id']
+        self.assertEqual(response.context['cl'].has_related_field_in_list_display(), False)
+
     def test_limited_filter(self):
         """Ensure admin changelist filters do not contain objects excluded via limit_choices_to.
         This also tests relation-spanning filters (e.g. 'color__value').