#24765: Calling flatten on a Context object fails in some cases
---------------------------------+--------------------
Reporter: poirier | Owner: nobody
Type: Bug | Status: new
Component: Template system | Version: 1.8
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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For example, if one of the "dicts" in the Context object is actually a
RequestContext. Here's the `flatten` method in Django 1.8.1 (from
django/template/context.py, line 101):
{{{
def flatten(self):
"""
Returns self.dicts as one dictionary
"""
flat = {}
for d in self.dicts:
flat.update(d)
return flat
}}}
The line `flat.update(d)` fails because a RequestContext doesn't provide
enough of a dictionary's interface to be used in an `update`, and you get
errors like:
{{{
File ".../lib/python2.7/site-packages/django/template/context.py",
line 107, in flatten
flat.update(d)
ValueError: dictionary update sequence element #0 has length 6; 2 is
required
}}}
It might be a little tricky to come up with a case where a Context ends up
with a RequestContext in it. I believe in my case it's happening when a
template uses an `inclusion_tag` type template tag that returns its
`context` argument, possibly modified, e.g.:
{{{
@register.inclusion_tag('template_fragment.html',
takes_context=True)
def some_tag(context):
context['thingy'] = 12
return context
}}}
The return value gets pushed onto the Context. During testing, the Context
ends up being returned in the list of Context objects in Response.context,
which is where I was trying to call flatten on it.
I don't know if the right fix is to make a RequestContext behave more like
a dictionary, or to avoid pushing RequestContext objects onto a Context,
or something else. I will probably work around for now by forcing the
return values from my inclusion_tags to be simple dictionaries.
Context.flatten:
https://docs.djangoproject.com/en/1.8/ref/templates/api/#django.template.Context.flatten
--
Ticket URL: <https://code.djangoproject.com/ticket/24765>
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