from django.core.exceptions import ImproperlyConfigured
from django.utils.importlib import import_module
# Cache of actual callables.
_standard_context_processors = None
# We need the CSRF processor no matter what the user has in their settings,
# because otherwise it is a security vulnerability, and we can't afford to leave
# this to human error or failure to read migration instructions.
_builtin_context_processors = ('django.core.context_processors.csrf',)
class ContextPopException(Exception):
"pop() has been called more times than push()"
pass
class BaseContext(object):
def __init__(self, dict_=None):
dict_ = dict_ or {}
self.dicts = [dict_]
def __repr__(self):
return repr(self.dicts)
def __iter__(self):
for d in reversed(self.dicts):
yield d
def push(self):
d = {}
self.dicts.append(d)
return d
def pop(self):
if len(self.dicts) == 1:
raise ContextPopException
return self.dicts.pop()
def __setitem__(self, key, value):
"Set a variable in the current context"
self.dicts[-1][key] = value
def __getitem__(self, key):
"Get a variable's value, starting at the current context and going upward"
for d in reversed(self.dicts):
if key in d:
return d[key]
raise KeyError(key)
def __delitem__(self, key):
"Delete a variable from the current context"
del self.dicts[-1][key]
def has_key(self, key):
for d in self.dicts:
if key in d:
return True
return False
def __contains__(self, key):
return self.has_key(key)
def get(self, key, otherwise=None):
for d in reversed(self.dicts):
if key in d:
return d[key]
return otherwise
class Context(BaseContext):
"A stack container for variable context"
def __init__(self, dict_=None, autoescape=True, current_app=None):
self.autoescape = autoescape
self.current_app = current_app
self.render_context = RenderContext()
super(Context, self).__init__(dict_)
def update(self, other_dict):
"Like dict.update(). Pushes an entire dictionary's keys and values onto the context."
if not hasattr(other_dict, '__getitem__'):
raise TypeError('other_dict must be a mapping (dictionary-like) object.')
self.dicts.append(other_dict)
return other_dict
class RenderContext(BaseContext):
"""
A stack container for storing Template state.
RenderContext simplifies the implementation of template Nodes by providing a
safe place to store state between invocations of a node's `render` method.
The RenderContext also provides scoping rules that are more sensible for
'template local' variables. The render context stack is pushed before each
template is rendered, creating a fresh scope with nothing in it. Name
resolution fails if a variable is not found at the top of the RequestContext
stack. Thus, variables are local to a specific template and don't affect the
rendering of other templates as they would if they were stored in the normal
template context.
"""
def __iter__(self):
for d in self.dicts[-1]:
yield d
def has_key(self, key):
return key in self.dicts[-1]
def get(self, key, otherwise=None):
d = self.dicts[-1]
if key in d:
return d[key]
return otherwise
# This is a function rather than module-level procedural code because we only
# want it to execute if somebody uses RequestContext.
def get_standard_processors():
from django.conf import settings
global _standard_context_processors
if _standard_context_processors is None:
processors = []
collect = []
collect.extend(_builtin_context_processors)
collect.extend(settings.TEMPLATE_CONTEXT_PROCESSORS)
for path in collect:
i = path.rfind('.')
module, attr = path[:i], path[i+1:]
try:
mod = import_module(module)
except ImportError, e:
raise ImproperlyConfigured('Error importing request processor module %s: "%s"' % (module, e))
try:
func = getattr(mod, attr)
except AttributeError:
raise ImproperlyConfigured('Module "%s" does not define a "%s" callable request processor' % (module, attr))
processors.append(func)
_standard_context_processors = tuple(processors)
return _standard_context_processors
class RequestContext(Context):
"""
This subclass of template.Context automatically populates itself using
the processors defined in TEMPLATE_CONTEXT_PROCESSORS.
Additional processors can be specified as a list of callables
using the "processors" keyword argument.
"""
def __init__(self, request, dict=None, processors=None, current_app=None):
Context.__init__(self, dict, current_app=current_app)
if processors is None:
processors = ()
else:
processors = tuple(processors)
for processor in get_standard_processors() + processors:
self.update(processor(request))
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