from contextlib import contextmanager
from copy import copy
# Hard-coded processor for easier use of CSRF protection.
_builtin_context_processors = ('django.template.context_processors.csrf',)
[文档]class ContextPopException(Exception):
"pop() has been called more times than push()"
pass
class ContextDict(dict):
def __init__(self, context, *args, **kwargs):
super().__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:
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())
duplicate.dicts = self.dicts[:]
return duplicate
def __repr__(self):
return repr(self.dicts)
def __iter__(self):
return reversed(self.dicts)
def push(self, *args, **kwargs):
dicts = []
for d in args:
if isinstance(d, BaseContext):
dicts += d.dicts[1:]
else:
dicts.append(d)
return ContextDict(self, *dicts, **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 set_upward(self, key, value):
"""
Set a variable in one of the higher contexts if it exists there,
otherwise in the current context.
"""
context = self.dicts[-1]
for d in reversed(self.dicts):
if key in d:
context = d
break
context[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 __contains__(self, key):
return any(key in d for d in self.dicts)
def get(self, key, otherwise=None):
for d in reversed(self.dicts):
if key in d:
return d[key]
return otherwise
def setdefault(self, key, default=None):
try:
return self[key]
except KeyError:
self[key] = default
return default
def new(self, values=None):
"""
Return 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):
"""
Return self.dicts as one dictionary.
"""
flat = {}
for d in self.dicts:
flat.update(d)
return flat
def __eq__(self, other):
"""
Compare two contexts by comparing theirs 'dicts' attributes.
"""
return (
isinstance(other, BaseContext) and
# because dictionaries can be put in different order
# we have to flatten them like in templates
self.flatten() == other.flatten()
)
[文档]class Context(BaseContext):
"A stack container for variable context"
def __init__(self, dict_=None, autoescape=True, use_l10n=None, use_tz=None):
self.autoescape = autoescape
self.use_l10n = use_l10n
self.use_tz = use_tz
self.template_name = "unknown"
self.render_context = RenderContext()
# Set to the original template -- as opposed to extended or included
# templates -- during rendering, see bind_template.
self.template = None
super().__init__(dict_)
@contextmanager
def bind_template(self, template):
if self.template is not None:
raise RuntimeError("Context is already bound to a template")
self.template = template
try:
yield
finally:
self.template = None
def __copy__(self):
duplicate = super().__copy__()
duplicate.render_context = copy(self.render_context)
return duplicate
[文档] def update(self, other_dict):
"Push 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.')
if isinstance(other_dict, BaseContext):
other_dict = other_dict.dicts[1:].pop()
return ContextDict(self, 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.
"""
template = None
def __iter__(self):
yield from self.dicts[-1]
def __contains__(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]
@contextmanager
def push_state(self, template, isolated_context=True):
initial = self.template
self.template = template
if isolated_context:
self.push()
try:
yield
finally:
self.template = initial
if isolated_context:
self.pop()
[文档]class RequestContext(Context):
"""
This subclass of template.Context automatically populates itself using
the processors defined in the engine's configuration.
Additional processors can be specified as a list of callables
using the "processors" keyword argument.
"""
def __init__(self, request, dict_=None, processors=None, use_l10n=None, use_tz=None, autoescape=True):
super().__init__(dict_, use_l10n=use_l10n, use_tz=use_tz, autoescape=autoescape)
self.request = request
self._processors = () if processors is None else tuple(processors)
self._processors_index = len(self.dicts)
# placeholder for context processors output
self.update({})
# empty dict for any new modifications
# (so that context processors don't overwrite them)
self.update({})
@contextmanager
def bind_template(self, template):
if self.template is not None:
raise RuntimeError("Context is already bound to a template")
self.template = template
# Set context processors according to the template engine's settings.
processors = (template.engine.template_context_processors +
self._processors)
updates = {}
for processor in processors:
updates.update(processor(self.request))
self.dicts[self._processors_index] = updates
try:
yield
finally:
self.template = None
# Unset context processors.
self.dicts[self._processors_index] = {}
def new(self, values=None):
new_context = super().new(values)
# This is for backwards-compatibility: RequestContexts created via
# Context.new don't include values from context processors.
if hasattr(new_context, '_processors_index'):
del new_context._processors_index
return new_context
def make_context(context, request=None, **kwargs):
"""
Create a suitable Context from a plain dict and optionally an HttpRequest.
"""
if context is not None and not isinstance(context, dict):
raise TypeError('context must be a dict rather than %s.' % context.__class__.__name__)
if request is None:
context = Context(context, **kwargs)
else:
# The following pattern is required to ensure values from
# context override those from template context processors.
original_context = context
context = RequestContext(request, **kwargs)
if original_context:
context.push(original_context)
return context
