Fixed #24316 -- Made ModelAdmin.list_display callables use an appropriate CSS class name.

Thanks Berker Peksag for the review.

django/contrib/admin/templatetags/admin_list.py

@@ -104,6 +104,7 @@ def result_headers(cl):
             return_attr=True
         )
         if attr:
+            field_name = _coerce_field_name(field_name, i)
             # Potentially not sortable
 
             # if the field is the action checkbox: no sorting and special class
@@ -183,6 +184,18 @@ def _boolean_icon(field_val):
     return format_html('<img src="{}" alt="{}" />', icon_url, field_val)
 
 
+def _coerce_field_name(field_name, field_index):
+    """
+    Coerce a field_name (which may be a callable) to a string.
+    """
+    if callable(field_name):
+        if field_name.__name__ == '<lambda>':
+            return 'lambda' + str(field_index)
+        else:
+            return field_name.__name__
+    return field_name
+
+
 def items_for_result(cl, result, form):
     """
     Generates the actual list of data.
@@ -197,9 +210,9 @@ def items_for_result(cl, result, form):
 
     first = True
     pk = cl.lookup_opts.pk.attname
-    for field_name in cl.list_display:
+    for field_index, field_name in enumerate(cl.list_display):
         empty_value_display = cl.model_admin.get_empty_value_display()
-        row_classes = ['field-%s' % field_name]
+        row_classes = ['field-%s' % _coerce_field_name(field_name, field_index)]
         try:
             f, attr, value = lookup_field(field_name, result, cl.model_admin)
         except ObjectDoesNotExist:

tests/admin_views/admin.py

@@ -90,7 +90,7 @@ class ChapterXtra1Admin(admin.ModelAdmin):
 class ArticleAdmin(admin.ModelAdmin):
     list_display = (
         'content', 'date', callable_year, 'model_year', 'modeladmin_year',
-        'model_year_reversed', 'section',
+        'model_year_reversed', 'section', lambda obj: obj.title,
     )
     list_editable = ('section',)
     list_filter = ('date', 'section')

tests/admin_views/tests.py

@@ -344,6 +344,15 @@ class AdminViewBasicTest(AdminViewBasicTestCase):
         # started with 3 articles, one was deleted.
         self.assertEqual(Section.objects.latest('id').article_set.count(), 2)
 
+    def test_change_list_column_field_classes(self):
+        response = self.client.get(reverse('admin:admin_views_article_changelist'))
+        # callables display the callable name.
+        self.assertContains(response, 'column-callable_year')
+        self.assertContains(response, 'field-callable_year')
+        # lambdas display as "lambda" + index that they appear in list_display.
+        self.assertContains(response, 'column-lambda8')
+        self.assertContains(response, 'field-lambda8')
+
     def test_change_list_sorting_callable(self):
         """
         Ensure we can sort on a list_display field that is a callable