from copy import copy
from django.utils.module_loading import import_string
# 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 ContextDict(dict):
def __init__(self, context, *args, **kwargs):
super(ContextDict, self).__init__(*args, **kwargs)
context.dicts.append(self)
self.context = context
def __enter__(self):
return self
def __exit__(self, *args, **kwargs):
self.context.pop()
class BaseContext(object):
def __init__(self, dict_=None):
self._reset_dicts(dict_)
def _reset_dicts(self, value=None):
builtins = {'True': True, 'False': False, 'None': None}
self.dicts = [builtins]
if value is not None:
self.dicts.append(value)
def __copy__(self):
duplicate = copy(super(BaseContext, self))
duplicate.dicts = self.dicts[:]
return duplicate
def __repr__(self):
return repr(self.dicts)
def __iter__(self):
for d in reversed(self.dicts):
yield d
def push(self, *args, **kwargs):
return ContextDict(self, *args, **kwargs)
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
def new(self, values=None):
"""
Returns a new context with the same properties, but with only the
values given in 'values' stored.
"""
new_context = copy(self)
new_context._reset_dicts(values)
return new_context
def flatten(self):
"""
Returns self.dicts as one dictionary
"""
flat = {}
for d in self.dicts:
flat.update(d)
return flat
def __eq__(self, other):
"""
Compares two contexts by comparing theirs 'dicts' attributes.
"""
if isinstance(other, BaseContext):
# because dictionaries can be put in different order
# we have to flatten them like in templates
return self.flatten() == other.flatten()
# if it's not comparable return false
return False
[docs]class Context(BaseContext):
"A stack container for variable context"
def __init__(self, dict_=None, autoescape=True, current_app=None,
use_l10n=None, use_tz=None):
self.autoescape = autoescape
self.current_app = current_app
self.use_l10n = use_l10n
self.use_tz = use_tz
self.render_context = RenderContext()
super(Context, self).__init__(dict_)
def __copy__(self):
duplicate = super(Context, self).__copy__()
duplicate.render_context = copy(self.render_context)
return duplicate
[docs] def update(self, other_dict):
"Pushes other_dict to the stack of dictionaries in 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):
return self.dicts[-1].get(key, otherwise)
def __getitem__(self, key):
return self.dicts[-1][key]
# 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:
func = import_string(path)
processors.append(func)
_standard_context_processors = tuple(processors)
return _standard_context_processors
[docs]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,
use_l10n=None, use_tz=None):
Context.__init__(self, dict_, current_app=current_app,
use_l10n=use_l10n, use_tz=use_tz)
if processors is None:
processors = ()
else:
processors = tuple(processors)
updates = dict()
for processor in get_standard_processors() + processors:
updates.update(processor(request))
self.update(updates)
Feb 24, 2017