• Language: en

Source code for django.template.context

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',)


[docs]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): yield from 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): for d in self.dicts: if key in d: return True return False 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() )
[docs]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
[docs] 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()
[docs]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
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