Fixed #11160 - Ensure full_clean is called from non_form_errors

Updated FormSet.non_form_errors() to ensure full_clean() has
been called before returning the errors.

django/forms/formsets.py

@@ -250,9 +250,9 @@ class BaseFormSet(object):
         form -- i.e., from formset.clean(). Returns an empty ErrorList if there
         are none.
         """
-        if self._non_form_errors is not None:
+        if self._non_form_errors is None:
-            return self._non_form_errors
+            self.full_clean()
-        return self.error_class()
+        return self._non_form_errors
 
     @property
     def errors(self):
@@ -291,9 +291,12 @@ class BaseFormSet(object):
 
     def full_clean(self):
         """
-        Cleans all of self.data and populates self._errors.
+        Cleans all of self.data and populates self._errors and
+        self._non_form_errors.
         """
         self._errors = []
+        self._non_form_errors = self.error_class()
+
         if not self.is_bound: # Stop further processing.
             return
         for i in range(0, self.total_form_count()):

tests/forms_tests/tests/test_formsets.py

@@ -972,6 +972,20 @@ class FormsFormsetTestCase(TestCase):
         finally:
             formsets.DEFAULT_MAX_NUM = _old_DEFAULT_MAX_NUM
 
+    def test_non_form_errors_run_full_clean(self):
+        # Regression test for #11160
+        # If non_form_errors() is called without calling is_valid() first,
+        # it should ensure that full_clean() is called.
+        class BaseCustomFormSet(BaseFormSet):
+            def clean(self):
+                raise ValidationError("This is a non-form error")
+
+        ChoiceFormSet = formset_factory(Choice, formset=BaseCustomFormSet)
+        formset = ChoiceFormSet(data, auto_id=False, prefix='choices')
+        self.assertTrue(isinstance(formset.non_form_errors(), ErrorList))
+        self.assertEqual(list(formset.non_form_errors()),
+            ['This is a non-form error'])
+
 
 data = {
     'choices-TOTAL_FORMS': '1', # the number of forms rendered