Avoided rewrapping Contexts in render_to_response.

This change preserves backwards-compatibility for a very common misuse
of render_to_response which even occurred in the official documentation.

It fixes that misuse wherever it happened in the code base and docs.

Context.__init__ is documented as accepting a dict and nothing else.
Since Context is dict-like, Context(Context({})) could work to some
extent. However, things get complicated with RequestContext and that
gets in the way of refactoring the template engine. This is the real
rationale for this change.

3 files changed, 19 insertions, 0 deletions

diff --git a/tests/shortcuts/tests.py b/tests/shortcuts/tests.py
index 4835b40797..24a73d4ffd 100644
--- a/tests/shortcuts/tests.py
+++ b/tests/shortcuts/tests.py
@@ -32,6 +32,15 @@ class ShortcutTests(TestCase):
         self.assertEqual(response.content, b'spam eggs\n')
         self.assertEqual(response['Content-Type'], 'text/html; charset=utf-8')
 
+    def test_render_to_response_with_context_instance_misuse(self):
+        """
+        For backwards-compatibility, ensure that it's possible to pass a
+        RequestContext instance in the dictionary argument instead of the
+        context_instance argument.
+        """
+        response = self.client.get('/render_to_response/context_instance_misuse/')
+        self.assertContains(response, 'context processor output')
+
     def test_render(self):
         response = self.client.get('/render/')
         self.assertEqual(response.status_code, 200)
diff --git a/tests/shortcuts/urls.py b/tests/shortcuts/urls.py
index cd18c8a01b..f02e74a745 100644
--- a/tests/shortcuts/urls.py
+++ b/tests/shortcuts/urls.py
@@ -7,6 +7,7 @@ urlpatterns = [
     url(r'^render_to_response/request_context/$', views.render_to_response_view_with_request_context),
     url(r'^render_to_response/content_type/$', views.render_to_response_view_with_content_type),
     url(r'^render_to_response/dirs/$', views.render_to_response_view_with_dirs),
+    url(r'^render_to_response/context_instance_misuse/$', views.render_to_response_with_context_instance_misuse),
     url(r'^render/$', views.render_view),
     url(r'^render/base_context/$', views.render_view_with_base_context),
     url(r'^render/content_type/$', views.render_view_with_content_type),
diff --git a/tests/shortcuts/views.py b/tests/shortcuts/views.py
index afae78d4d8..c75d324a34 100644
--- a/tests/shortcuts/views.py
+++ b/tests/shortcuts/views.py
@@ -33,6 +33,15 @@ def render_to_response_view_with_dirs(request):
     return render_to_response('render_dirs_test.html', dirs=dirs)
 
 
+def context_processor(request):
+    return {'bar': 'context processor output'}
+
+
+def render_to_response_with_context_instance_misuse(request):
+    context_instance = RequestContext(request, {}, processors=[context_processor])
+    # Incorrect -- context_instance should be passed as a keyword argument.
+    return render_to_response('shortcuts/render_test.html', context_instance)
+
 def render_view(request):
     return render(request, 'shortcuts/render_test.html', {
         'foo': 'FOO',