[1.8.x] Fixed #26267 -- Fixed BoundField to reallow slices of subwidgets.

Backport of b412681359 from master

django/forms/forms.py

@@ -554,7 +554,7 @@ class BoundField(object):
     def __getitem__(self, idx):
         # Prevent unnecessary reevaluation when accessing BoundField's attrs
         # from templates.
-        if not isinstance(idx, six.integer_types):
+        if not isinstance(idx, six.integer_types + (slice,)):
             raise TypeError
         return list(self.__iter__())[idx]
 

docs/releases/1.8.10.txt

@@ -24,3 +24,5 @@ Bugfixes
 
 * Reallowed dashes in top-level domain names of URLs checked by
   ``URLValidator`` to fix a regression in Django 1.8 (:ticket:`26204`).
+
+* Fixed ``BoundField`` to reallow slices of subwidgets (:ticket:`26267`).

docs/spelling_wordlist

@@ -512,6 +512,7 @@ quoteless
 Radziej
 rc
 readded
+reallow
 reallowed
 rebase
 rebased

tests/forms_tests/tests/test_forms.py

@@ -468,6 +468,20 @@ class FormsTestCase(TestCase):
         f = BeatleForm(auto_id=False)
         self.assertHTMLEqual('\n'.join(str(bf) for bf in f['name']), '<input type="text" name="name" />')
 
+    def test_boundfield_slice(self):
+        class BeatleForm(Form):
+            name = ChoiceField(
+                choices=[('john', 'John'), ('paul', 'Paul'), ('george', 'George'), ('ringo', 'Ringo')],
+                widget=RadioSelect,
+            )
+
+        f = BeatleForm()
+        bf = f['name']
+        self.assertEqual(
+            [str(item) for item in bf[1:]],
+            [str(bf[1]), str(bf[2]), str(bf[3])],
+        )
+
     def test_forms_with_multiple_choice(self):
         # MultipleChoiceField is a special case, as its data is required to be a list:
         class SongForm(Form):