Fixed #29247 -- Allowed blank model field choice to be defined in nested choices.

django/db/models/fields/__init__.py

@@ -816,8 +816,7 @@ class Field(RegisterLookupMixin):
         if self.choices:
             choices = list(self.choices)
             if include_blank:
-                named_groups = isinstance(choices[0][1], (list, tuple))
-                blank_defined = not named_groups and any(choice in ('', None) for choice, __ in choices)
+                blank_defined = any(choice in ('', None) for choice, _ in self.flatchoices)
                 if not blank_defined:
                     choices = blank_choice + choices
             return choices

tests/model_fields/tests.py

@@ -140,6 +140,19 @@ class GetChoicesTests(SimpleTestCase):
         f = models.CharField(choices=choices)
         self.assertEqual(f.get_choices(include_blank=True), choices)
 
+    def test_blank_in_grouped_choices(self):
+        choices = [
+            ('f', 'Foo'),
+            ('b', 'Bar'),
+            ('Group', (
+                ('', 'No Preference'),
+                ('fg', 'Foo'),
+                ('bg', 'Bar'),
+            )),
+        ]
+        f = models.CharField(choices=choices)
+        self.assertEqual(f.get_choices(include_blank=True), choices)
+
     def test_lazy_strings_not_evaluated(self):
         lazy_func = lazy(lambda x: 0 / 0, int)  # raises ZeroDivisionError if evaluated.
         f = models.CharField(choices=[(lazy_func('group'), (('a', 'A'), ('b', 'B')))])