From 0154702a987bd06d20e53fe23284b2c4a93b9063 Mon Sep 17 00:00:00 2001
From: Alex Morozov <inductor2000@mail.ru>
Date: Tue, 10 Nov 2015 16:06:59 +0300
Subject: [PATCH] [1.9.x] Fixed #25548 -- Prevented FormView.form_invalid()
 from discarding its form argument.

Backport of e171a83b1516a3a2a393a5300527af1aab21c213 from master
---
 django/views/generic/edit.py     |  2 +-
 docs/releases/1.9.1.txt          |  3 +++
 tests/generic_views/test_edit.py |  7 +++++++
 tests/generic_views/urls.py      |  2 ++
 tests/generic_views/views.py     | 10 ++++++++++
 5 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/django/views/generic/edit.py b/django/views/generic/edit.py
index 9120e1dd76..4ebf06a497 100644
--- a/django/views/generic/edit.py
+++ b/django/views/generic/edit.py
@@ -112,7 +112,7 @@ class FormMixin(six.with_metaclass(FormMixinBase, ContextMixin)):
         If the form is invalid, re-render the context data with the
         data-filled form and errors.
         """
-        return self.render_to_response(self.get_context_data())
+        return self.render_to_response(self.get_context_data(form=form))
 
     def get_context_data(self, **kwargs):
         """
diff --git a/docs/releases/1.9.1.txt b/docs/releases/1.9.1.txt
index 91a0f33a2a..e7c0bfeceb 100644
--- a/docs/releases/1.9.1.txt
+++ b/docs/releases/1.9.1.txt
@@ -11,3 +11,6 @@ Bugfixes
 
 * Fixed ``BaseCache.get_or_set()`` with the ``DummyCache`` backend
   (:ticket:`25840`).
+
+* Fixed a regression in ``FormMixin`` causing forms to be validated twice
+  (:ticket:`25548`).
diff --git a/tests/generic_views/test_edit.py b/tests/generic_views/test_edit.py
index e93965a670..e0730b1118 100644
--- a/tests/generic_views/test_edit.py
+++ b/tests/generic_views/test_edit.py
@@ -98,6 +98,13 @@ class BasicFormTests(TestCase):
         res = self.client.post('/contact/', {'name': "Me", 'message': "Hello"})
         self.assertRedirects(res, '/list/authors/')
 
+    def test_late_form_validation(self):
+        """
+        A form can be marked invalid in the form_valid() method (#25548).
+        """
+        res = self.client.post('/late-validation/', {'name': "Me", 'message': "Hello"})
+        self.assertFalse(res.context['form'].is_valid())
+
 
 class ModelFormMixinTests(SimpleTestCase):
     def test_get_form(self):
diff --git a/tests/generic_views/urls.py b/tests/generic_views/urls.py
index d455924a9e..85a6243b7f 100644
--- a/tests/generic_views/urls.py
+++ b/tests/generic_views/urls.py
@@ -65,6 +65,8 @@ urlpatterns = [
     # FormView
     url(r'^contact/$',
         views.ContactView.as_view()),
+    url(r'^late-validation/$',
+        views.LateValidationView.as_view()),
 
     # Create/UpdateView
     url(r'^edit/artists/create/$',
diff --git a/tests/generic_views/views.py b/tests/generic_views/views.py
index b40bbe92f0..b66418eb7b 100644
--- a/tests/generic_views/views.py
+++ b/tests/generic_views/views.py
@@ -307,3 +307,13 @@ class NonModelDetail(generic.DetailView):
 class ObjectDoesNotExistDetail(generic.DetailView):
     def get_queryset(self):
         return Book.does_not_exist.all()
+
+
+class LateValidationView(generic.FormView):
+    form_class = ContactForm
+    success_url = reverse_lazy('authors_list')
+    template_name = 'generic_views/form.html'
+
+    def form_valid(self, form):
+        form.add_error(None, 'There is an error')
+        return self.form_invalid(form)