[Django] #35417: RequestContext.new creates a context that cannot be flattened

#35417: RequestContext.new creates a context that cannot be flattened
-----------------------------------------+------------------------
               Reporter:  Lily Foote     |          Owner:  nobody
                   Type:  Uncategorized  |         Status:  new
              Component:  Uncategorized  |        Version:  5.0
               Severity:  Normal         |       Keywords:
           Triage Stage:  Unreviewed     |      Has patch:  0
    Needs documentation:  0              |    Needs tests:  0
Patch needs improvement:  0              |  Easy pickings:  0
                  UI/UX:  0              |
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 In
 
[https://github.com/django/django/blob/c187f5f9242b681abaa199173e02066997439425/django/template/library.py#L273
 InclusionNode.render] Django creates a {{{new_context}}} from two existing
 contexts ({{{context}}} and {{{_dict}}}) by calling {{{new_context =
 context.new(_dict)}}}. These can both be instances of {{{RequestContext}}}
 leading to {{{new_context}}} also being a {{{RequestContext}}} (I have not
 tried with any other context types). However, calling
 {{{new_context.flatten()}}} raises a {{{ValueError}}}:

 {{{
 ValueError: dictionary update sequence element #0 has length 1; 2 is
 required
 }}}

 I can reproduce this in a small test:

 {{{
 from django.template.context import RequestContext
 from django.test import RequestFactory, TestCase


 class RequestContextTestCase(TestCase):
     def test_flatten_request_context_new(self):
         factory = RequestFactory()

         request = factory.get("/foo/")
         context = RequestContext(request)
         context_2 = RequestContext(request)
         context_3 = context.new(context_2)

         self.assertEqual(
             context_3.flatten(), {"False": False, "None": None, "True":
 True}
         )
 }}}

 I discovered this when running Kolo on a Django admin view
 (http://127.0.0.1:8000/admin/auth/user/). Kolo calls
 {{{context.flatten()}}} internally when introspecting a template during
 rendering, which leads to this exception:

 {{{
 Traceback (most recent call last):
   File "/home/lily/work/kloppindustries/kolo/python/src/kolo/profiler.py",
 line 170, in __call__
     frame_data = processor.process(
                  ^^^^^^^^^^^^^^^^^^
   File "/home/lily/work/kloppindustries/kolo/python/src/kolo/plugins.py",
 line 107, in process
     data.update(self.process_extra(frame, event, arg, self.context))
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   File
 "/home/lily/work/kloppindustries/kolo/python/src/kolo/filters/django.py",
 line 89, in process_django_template
     template_context = template_context.flatten()
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^
   File "/home/lily/.local/share/lilyenv/virtualenvs/kolo-
 sandbox/3.12/lib/python3.12/site-packages/django/template/context.py",
 line 120, in flatten
     flat.update(d)
 ValueError: dictionary update sequence element #0 has length 3; 2 is
 required
 }}}
-- 
Ticket URL: <https://code.djangoproject.com/ticket/35417>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

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